Part I: Electrolytes are ubiquitous in our world and play essential roles in biology, consumer products, and energy storage. Fundamentally, an electrolyte consists of charged species and a solvent, both of which significantly influence its behavior in the bulk and near interfaces. While it is relatively straightforward to predict charge interactions in a vacuum, the presence of a liquid solvent mediates these interactions in complex and nontrivial ways. Moreover, the interaction of ions with surfaces is highly nuanced and can be strongly affected by the specific chemistry of the ions, solvent, and interface. This is especially relevant in the context of the electric double layer, a subject of scientific inquiry since 1853. Gaining a deeper understanding of these intricate effects and how they govern electrolyte behavior is critical not only for explaining biologically relevant phenomena such as macromolecular complexation, but also for designing batteries and supercapacitors with optimized energy storage performance.
\r\n\r\nThis work presents an analysis of three distinct systems in which the behavior of charged and polar fluids were poorly understood. One area of focus is the effect of introducing non-polar solvents on the charging behavior and energy storage performance of room-temperature ionic liquid supercapacitors, with particular attention to specific surface effects and complex tricritical surface phase behavior. Another topic explored is the entropic origin of ionic interactions in polar solvents, highlighting how entropy is the dominant force driving ion association. Separately, we also investigate the unique surface polarization that arises in asymmetric polar fluids at liquid\u2013vapor interfaces, revealing subtle interfacial phenomena driven solely by molecular asymmetry.
\r\n\r\nPart II: Block copolymers can undergo microphase separation to form a range of ordered nanostructures, including lamellae, lattice-ordered spheres and cylinders, and even network phases. In selective solvents, they self-assemble into micelles, similar to surfactant molecules. However, unlike surfactants, block copolymers often contain hundreds or thousands of repeat units, which significantly slows their dynamics and equilibration. As a result, solutions of diblock copolymer micelles are frequently kinetically trapped far from equilibrium due to large free energy barriers associated with equilibration mechanisms such as chain exchange, micelle fusion, and micelle fission. For applications ranging from viscosity modification and drug delivery to nanoreactors, understanding these kinetic processes is essential. Moreover, developing strategies to achieve consistent and stable micelle size distributions remains a key challenge, particularly in systems far from equilibrium.
\r\n\r\nThis work analyzes the single-chain exchange mechanism in highly segregated copolymer micelles, with particular attention to its chain length dependence, a topic that has been actively debated since the introduction of the Halperin and Alexander theory in 1989. The kinetics of chain exchange are examined under two representative regimes: one involving polymeric solvents, where the micelle core gradually shrinks, and the other involving small-molecule solvents, where the core fully collapses. A combination of simulation and sampling techniques is employed to compare the thermodynamics of the underlying free energy landscape with the actual kinetic pathways of chain escape.
\r\n\r\nThis work also analyzes the kinetic pathways involved in a widely used copolymer micelle preparation technique known as thin film dissolution, or direct dissolution. Mesoscale molecular dynamics simulations are performed to provide a molecular-level picture of micelle formation, starting from both ordered and disordered initial states. In parallel, a mean-field theory is developed to assess how closely the intermediate structures and the final micelles resemble equilibrium configurations.
", "doi": "10.7907/p5ca-t067", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:17783", "collection": "thesis", "collection_id": "17783", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12042025-001904943", "type": "thesis", "title": "Degradation Mechanisms of Oxide Ceramics Under Molten Regolith Electrolysis Conditions", "author": [ { "family_name": "Yu", "given_name": "Kevin", "orcid": "0000-0003-3130-4309", "clpid": "Yu-Kevin" } ], "thesis_advisor": [ { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "thesis_committee": [ { "family_name": "Fultz", "given_name": "Brent T.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B-T" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Ravichandran", "given_name": "Guruswami", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Molten regolith electrolysis (MRE) is a promising in situ resource utilization process that produces both metals and O2 through the direct electrolysis of molten lunar regolith (dirt), in support of a permanent human presence on the Moon. However, MRE requires an operational temperature of 1600\u00b0C, involves contact with corrosive molten regolith, and causes an oxidizing atmosphere during electrolysis. These conditions prevent the usage of many refractory materials due to rapid degradation. Moreover, there are additional challenges associated with MRE, such as bubble detachment and O2 collection at the anode.
\r\n\r\nIn this thesis, a hollow anode design, composed of an oxygen-conducting yttria-stabilized zirconia (YSZ) shell and a platinum current collector, is presented to address the challenges of MRE. Research is performed to evaluate the performance of YSZ electrolytes and containment materials in the extreme MRE environment and identify the mechanisms governing their degradation. From these experiments, a laboratory-scale MRE cell is designed and fabricated to support hollow anode testing. Electrolysis experiments with lunar regolith simulants successfully demonstrate sustained oxygen production for up to 12 hours. Extended testing with a degradation mitigation strategy further increases O2 production efficiencies and enables cumulative operation of 40 hours, establishing design life estimates for YSZ hollow anodes and guidelines for integration into industrial-scale MRE systems.
\r\n\r\nA previously unreported Sc2O3-rich phase, silicon aluminum scandate (SAS), is discovered while performing materials compatibility testing. The crystal structure of SAS is solved using microcrystal electron diffraction, and its material properties are characterized. These results indicate that SAS is an entropy-stabilized oxide with potential applications as a thermally insulating, refractory oxide material.
\r\n\r\nUltimately, the work presented demonstrates the feasibility of YSZ hollow anodes for MRE and expands the understanding of ceramic behavior in molten oxide environments. The successful production of O2 with a hollow anode provides a foundation for scaling MRE toward industrial operation on the lunar surface, while the discovery of SAS highlights the potential for uncovering new oxide materials in extreme environments.
", "doi": "10.7907/41bv-7696", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:17716", "collection": "thesis", "collection_id": "17716", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10072025-232922980", "primary_object_url": { "basename": "mchaffie_daniel_2026_redacted.pdf", "content": "final", "filesize": 43106664, "license": "other", "mime_type": "application/pdf", "url": "/17716/2/mchaffie_daniel_2026_redacted.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "Computational and Data-Driven Discovery of Li Solid-State Electrolytes: From Representation to Experimental Realization", "author": [ { "family_name": "McHaffie", "given_name": "Daniel Brendan", "orcid": "0000-0002-7265-7584", "clpid": "McHaffie-Daniel-Brendan" } ], "thesis_advisor": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "thesis_committee": [ { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" }, { "family_name": "Bernardi", "given_name": "Marco", "orcid": "0000-0001-7289-9666", "clpid": "Bernardi-Marco" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Improvements in energy storage are required to facilitate the transition to renewable energy and the electrification of transport. Lithium-ion batteries (LIBs) are a promising solution, but the current leading chemistry, consisting of a layered oxide cathode and a graphite anode separated by a liquid electrolyte, has been optimized to near-theoretical limits. Replacing the graphitic carbon with Li metal would significantly improve energy density but the instability of the Li metal-electrolyte interface introduces performance and safety challenges. Using a solid-state electrolyte (SSE) to construct an all-solid-state battery (ASSB) could mitigate these issues. However, an ideal SSE material has yet to be identified.
\r\n \r\nThousands of known Li-containing materials have not yet been evaluated as SSEs. Data-driven methods could prioritize materials for experimental study but have historically lacked sufficient data and optimal representations. Chapter 2 presents the largest structure-ionic conductivity database to date and uses semi-supervised learning to determine the highest-performing descriptors. From ~26,000 Li-containing materials, 212 candidates are identified and screened using semi-empirical and first-principles calculations. Li3BS3 exhibits ionic conductivity above 10-3 S cm-1 with defect engineering through substitution and mechanical milling.
\r\n \r\nChapter 3 explores Cl, Al, and Si substitution in Li3BS3 to reveal mechanisms of ionic conductivity enhancement. At low substitution levels, conductivity improvements are driven by disordered environments from reduced crystallinity and microstructural effects. For Cl and Al, higher substitution generates fully amorphous phases with ionic conductivity above 10-4 S cm-1. Sufficient Si substitution produces novel crystalline phases with conductivities exceeding 10-3 S cm-1.
\r\n \r\nPrevious approaches, such as that in Chapter 2, could not represent disordered compounds, excluding much of the training data and candidate materials. This is particularly significant given the importance of disorder highlighted in Chapters 2 and 3 and the prevalence of disorder in known superionic conductors. Chapter 4 implements a transfer-learned graph representation compatible with disordered structures. A larger database is curated and used to train models for screening all known Li-containing materials. Experimental validation of superionic conductivity in an identified candidate demonstrates the utility of this graph-based approach for discovering experimentally relevant, high-performance materials.
", "doi": "10.7907/fn7h-vz84", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:17669", "collection": "thesis", "collection_id": "17669", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09052025-191750417", "type": "thesis", "title": "Developing New Methods of Quantum Spectroscopy with Nonlinear Integrated Photonics", "author": [ { "family_name": "Harper", "given_name": "Nathan Andrew", "orcid": "0000-0001-8727-0932", "clpid": "Harper-Nathan-Andrew" } ], "thesis_advisor": [ { "family_name": "Cushing", "given_name": "Scott K.", "orcid": "0000-0003-3538-2259", "clpid": "Cushing-Scott-K" } ], "thesis_committee": [ { "family_name": "Hadt", "given_name": "Ryan G.", "orcid": "0000-0001-6026-1358", "clpid": "Hadt-Ryan-G" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" }, { "family_name": "Cushing", "given_name": "Scott K.", "orcid": "0000-0003-3538-2259", "clpid": "Cushing-Scott-K" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Photon pairs produced through spontaneous parametric down-conversion exhibit entanglement in their time-energy degrees of freedom, offering sub-100 fs entanglement times while simultaneously exhibiting a joint energy resolution dictated by that of the continuous-wave pump laser. While entangled photon pairs have found many applications in sensing and imaging, taking advantage of their ultrafast correlations has proven to be more difficult.
\r\n\r\nIn this dissertation, we advance a number of practical aspects of spectroscopy with entangled pairs of photons. First, we show that the ultrafast correlations in photon pairs are useful for fluorescence lifetime measurements, enabling a CW laser to perform time-resolved measurements through a simple heralding scheme. Next, we develop bright, efficient, and single spatial mode sources of entangled photons using thin-film lithium niobate nanophotonics, bringing these devices to the visible and near-IR for the first time. In the process, we develop a source of UV light and investigate the performance of thin-film lithium niobate for evanescent sensing. Finally, we show promising results that two down-conversion processes in the same waveguide can be cascaded to generate entangled photon triplets with high efficiency, enabling pairs of photons to be heralded.
", "doi": "10.7907/j0x1-5742", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:17243", "collection": "thesis", "collection_id": "17243", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05192025-180916338", "type": "thesis", "title": "Elucidating the Role of Transition Metal Electronic Structure in Catalysis and Spin Relaxation", "author": [ { "family_name": "Luedecke", "given_name": "Kaitlin Mary", "orcid": "0000-0002-8163-9417", "clpid": "Luedecke-Kaitlin-Mary" } ], "thesis_advisor": [ { "family_name": "Hadt", "given_name": "Ryan", "orcid": "0000-0001-6026-1358", "clpid": "Hadt-Ryan-G" } ], "thesis_committee": [ { "family_name": "Cushing", "given_name": "Scott K.", "orcid": "0000-0003-3538-2259", "clpid": "Cushing-Scott-K" }, { "family_name": "Hadt", "given_name": "Ryan", "orcid": "0000-0001-6026-1358", "clpid": "Hadt-Ryan-G" }, { "family_name": "Agapie", "given_name": "Theodor", "orcid": "0000-0002-9692-7614", "clpid": "Agapie-T" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Transition metal complexes are the workhorses of physical inorganic chemistry and have diverse applications in catalysis and quantum information science, especially. The primary descriptor of transition metal complexes, and a good predictor of their utility, is their electronic structure. Notably, rigorous characterization of the spin states, oxidation states, excited states, and magnetic properties of these complexes is necessary to gain mechanistic detail for these applications; this thesis focuses on elucidating the role of transition metal electronic structure in catalysis and spin relaxation. Chapter 1 introduces important transition metal electronic structure considerations and motivates these studies. Part I includes Chapters 2\u20134 and considers complexes relevant for CO\u2082 reduction chemistry and cross-coupling reactivity. Chapter 2 investigates the conditions under which a CO\u2082 reduction catalyst, Fe-p-TMA, undergoes speciation changes and characterizes its excited-state identities and lifetimes. Chapter 3 considers the electrochemical conditions under which highly reduced CO reduction products are generated in an iron porphyrin system, and important connections to photocatalysis are made. Chapter 4 compares the excited-state identities and reactivities of prototypical and tethered Ni(II)\u2013bpy aryl halide complexes. Part 2 includes Chapters 5\u20136 and focuses on spin relaxation, a key figure of merit in quantum information science. Chapter 5 investigates the effect of structural distortions in S = \u00bd copper porphyrin systems on their spin-lattice relaxation times, and Chapter 6 moves to identifying the mechanism of spin relaxation in an S = 1 Cr(o-tolyl)\u2084 system. Together, these compiled studies reveal the nuanced roles of transition metal electronic structure in catalysis and spin relaxation and highlight the importance of their characterization for developing optimized systems.", "doi": "10.7907/7t77-rd65", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:17233", "collection": "thesis", "collection_id": "17233", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05152025-202058082", "primary_object_url": { "basename": "Stradley_Thesis.pdf", "content": "final", "filesize": 41167317, "license": "other", "mime_type": "application/pdf", "url": "/17233/3/Stradley_Thesis.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Materials and Interfaces to Enable Reversible Mg Electrochemistry for Energy Storage Applications", "author": [ { "family_name": "Stradley", "given_name": "Steven Hartzel", "orcid": "0009-0009-7154-608X", "clpid": "Stradley-Steven-Hartzel" } ], "thesis_advisor": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "thesis_committee": [ { "family_name": "Wang", "given_name": "Zhen-Gang", "orcid": "0000-0002-3361-6114", "clpid": "Wang-Zhen-Gang" }, { "family_name": "Giapis", "given_name": "Konstantinos P.", "orcid": "0000-0002-7393-298X", "clpid": "Giapis-K-P" }, { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Climate change drives the need for a dramatically increased deployment of electric vehicles and intermittent renewable energy sources. Each of these depends intimately on batteries for range and reliability. Although Li-ion batteries are the current industry standard for electrochemical energy storage, they are based on scarce and unevenly distributed resources. It is thus crucial to develop rechargeable battery chemistries based on more energy dense and resource equitable materials. Orders of magnitude more abundant and energy dense than Li, Mg is an attractive alternative to Li for energy storage. Despite its many attractive properties, deployment of Mg-based chemistries is hindered by a lack of cathode, anode, and electrolyte materials which support Mg electrochemistry and are mutually compatible. This thesis endeavors to deploy new materials to sustain reversible Mg electrochemistry and to understand how certain material properties impact electrochemical performance. First, we investigate new cathode materials based on Earth-abundant transition metal chlorides. These cathodes cycle somewhat reversibly but are prone to rapid capacity fade due to active material dissolution and shuttle. We identify electrolyte modification as a means to combat this fade. Next, we characterize halide-free Mg electrolytes based on weakly coordinating Si-centered anions. These electrolytes display impressively high oxidative stabilities but also relatively high reductive overpotentials and a fatal vulnerability to passivation by H\u2082O. We then consider a class of electrolytes based on B-centered anions with aryl ligands. These systems show exceptionally low reductive overpotentials among halide-free Mg electrolytes. We increase the bulk of the anion and correspondingly observe a slight increase in the reductive overpotential and an enhancement in rate performance. Though this class of compounds shows a low oxidative stability, the structure-property relationships gleaned from it may prove useful in future electrolyte studies. Finally, we deploy Al as an Earth-abundant, high capacity alloying anode for Mg-based batteries. Though the native kinetics for Mg-Al alloying prove too sluggish for practical systems, we use Bi to enhance the alloying kinetics of Al by two orders of magnitude. Though alloying capacity is limited by a large particle size, we present a viable method for enhancing Al alloying kinetics to relevant rates, thereby unlocking a highly desirable material for future studies. Taken together, this work expands the scope of cathode, electrolyte, and anode materials which support reversible Mg electrochemistry. Though imperfect, the lessons we learn from them may inform future design decisions to enable reversible Mg-based batteries.", "doi": "10.7907/vs2j-ep54", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:17192", "collection": "thesis", "collection_id": "17192", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05022025-025023583", "type": "thesis", "title": "Beyond Li: Challenges in Moving Towards Earth-Abundant Battery Materials", "author": [ { "family_name": "Qian", "given_name": "Michelle Dena", "orcid": "0000-0002-4815-1014", "clpid": "Qian-Michelle-Dena" } ], "thesis_advisor": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "thesis_committee": [ { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Hadt", "given_name": "Ryan G.", "orcid": "0000-0001-6026-1358", "clpid": "Hadt-Ryan-G" }, { "family_name": "Manthiram", "given_name": "Karthish", "orcid": "0000-0001-9260-3391", "clpid": "Manthiram-Karthish" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Batteries are a necessary component towards the advancement and proliferation of modern day technology, and are also an essential piece of the transition towards renewable energy. The lithium-ion battery (LIB) is the most common type of rechargeable battery, and the archetype relies on a traditional layered transition metal oxide cathode, organic electrolyte with a lithium salt, and a graphite anode. The design of these cells has been optimized to the point that the energy densities in these batteries are approaching their theoretical capacities. Combined with the supply chain challenges associated with many typical cathode elements and increasing energy demand, this highlights the need for new earth-abundant, high energy density battery technology. This thesis addresses challenges in two such systems: Mg-S and sodium-ion batteries (SIBs). Mg-S batteries suffer from capacity fade related to the polysulfide shuttle effect, which results in loss of active material and passivation of the anode. Here, we demonstrate that the rate of passivation is inversely proportional to the chain length of the polysulfides present in solution, and that passivation can be slowed or even reversed through addition of S\u2088 and the consequent perturbation of existing polysulfide speciation equilibria. SIBs are frequently touted as a \"drop-in\" technology for LIBs due to both systems relying on mobile alkali ions, but SIBs have inherently lower energy densities due to larger Na\u207a ion. In Chapters 3 and 4 we explore anion redox as a method of increasing energy densities in SIBs--Chapter 3 shows that in LiNaFeS\u2082, the charge compensation mechanisms from Li and Na cycling are identical. However, Na\u207a cycling is worsened compared to Li\u207a by structural degradation from the removal and insertion of the bulky Na\u207a ion, emphasizing the differences that exist between optimizing SIB cathode performance compared with that of LIBs. In Chapter 4, we aim to develop structure-property relationships that enable a stronger understanding of anion redox that can be leveraged to design high energy density, multielectron redox cathodes. Through the examination of the electrochemically inactive NaCu1.5Fe0.5S\u2082 and its vacancy-containing derivative NaCu1.125Fe0.625S\u2082, we show that vacancies in the transition metal layer enable redox although the redox is observed occurs on the transition metals. The study also demonstrates potential limitations of ideal model systems and bulk spectroscopic analysis techniques in materials with low degrees of redox.
", "doi": "10.7907/s5ws-m162", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:16765", "collection": "thesis", "collection_id": "16765", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09272024-204111663", "type": "thesis", "title": "Electron Dynamics in Molecular Qubits and Catalytic Films", "author": [ { "family_name": "Mirzoyan", "given_name": "Ruben", "orcid": "0000-0002-2334-4012", "clpid": "Mirzoyan-Ruben" } ], "thesis_advisor": [ { "family_name": "Hadt", "given_name": "Ryan G.", "orcid": "0000-0001-6026-1358", "clpid": "Hadt-Ryan-G" } ], "thesis_committee": [ { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "Hadt", "given_name": "Ryan G.", "orcid": "0000-0001-6026-1358", "clpid": "Hadt-Ryan-G" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Winkler", "given_name": "Jay Richmond", "orcid": "0000-0002-4453-9716", "clpid": "Winkler-J-R" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Two significant areas within molecular and materials chemistry are explored: spin-phonon coupling in molecular qubits and electrocatalysis in cobalt oxyhydroxide thin films, detailed over four chapters and an appendix. The first chapter reviews advancements in molecular quantum information science, focusing on decoherence mechanisms in transition metal complex-based qubits, and introduces a dynamic ligand field model that categorizes decoherence regimes and designs qubits for various environments. The second chapter develops and enhances a ligand field theory model to quantify spin-phonon interactions in transition metal complexes, correlating theoretical insights with experimental data to improve quantum coherence in molecular qubits. The third chapter investigates the electron transport and dynamic defect states in cobalt-phosphate and cobalt-borate oxyhydroxide films, crucial for understanding their photoexcited states in oxygen evolution catalysis. The fourth chapter presents a novel magneto-electrochemical setup that quantifies magnetoenhancement in electrocatalytic current for water splitting, highlighting the potential of magnetic fields in enhancing electrocatalytic processes. This work provides both a physical inorganic framework and experimental insights for ongoing and future developments in molecular quantum information science and energy conversion.", "doi": "10.7907/mcq5-js86", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:17399", "collection": "thesis", "collection_id": "17399", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06032025-064811859", "type": "thesis", "title": "Multielectron Redox in Lithium-Rich, Industrial-Element Sulfides for High Energy Density Lithium-Ion Battery Cathodes", "author": [ { "family_name": "Patheria", "given_name": "Eshaan Salim", "orcid": "0000-0002-2761-8498", "clpid": "Patheria-Eshaan-Salim" } ], "thesis_advisor": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "thesis_committee": [ { "family_name": "Chan", "given_name": "Garnet K.", "orcid": "0000-0001-8009-6038", "clpid": "Chan-G-K" }, { "family_name": "Hadt", "given_name": "Ryan G.", "orcid": "0000-0001-6026-1358", "clpid": "Hadt-Ryan-G" }, { "family_name": "Manthiram", "given_name": "Karthish", "orcid": "0000-0001-9260-3391", "clpid": "Manthiram-Karthish" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This thesis develops a thermodynamic and electronic framework for lithium-ion battery cathodes and applies it to a new class of high-capacity sulfides composed exclusively of industrially abundant elements.\r\nIt introduces lithium-rich cathodes composed of aluminum, iron, and sulfur that leverage reversible multielectron anion redox, in which the formation and cleavage of sulfur-sulfur bonds enable especially high extents of charge storage.\r\nA core design framework is established linking delithiated-phase stability to accessible electrochemical redox capacity.\r\nThe chemical space is expanded with copper-substituted phases, in which unique copper-sulfur electronic interactions delocalize charge compensation beyond sulfur-sulfur bonds, thereby improving the reversibility of anion redox.\r\nThese materials achieve high energy densities using only industrial elements, offering a promising foundation for next-generation lithium-ion cathodes that address both performance and raw materials constraints.\r\nThus, this thesis advances the long-term goal of building more sustainable energy systems and expanding access to electricity worldwide.", "doi": "10.7907/2pdg-hs94", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:17097", "collection": "thesis", "collection_id": "17097", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03272025-184257192", "type": "thesis", "title": "Investigation and Control of the Electrode/Electrolyte Interface in Electrochemical Systems", "author": [ { "family_name": "Lee", "given_name": "Brian Chansol", "orcid": "0000-0002-0898-0838", "clpid": "Lee-Brian-Chansol" } ], "thesis_advisor": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "thesis_committee": [ { "family_name": "Agapie", "given_name": "Theodor", "orcid": "0000-0002-9692-7614", "clpid": "Agapie-T" }, { "family_name": "Cushing", "given_name": "Scott K.", "orcid": "0000-0003-3538-2259", "clpid": "Cushing-Scott-K" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "In electrochemical reactions, the electrode/electrolyte interface is of vital importance, as no reactivity occurs in the bulk electrode or the electrolyte. Often, the interface can be the difference between a successful reaction and a failure. In this thesis, we present three works wherein the electrode/electrolyte interface is studied and controlled to drive desired electrochemical reactivity. A Mg-In alloy is employed for Mg metal batteries to prevent Mg dendrite growth, which can cause cell shorting and failure. By coating the surface of Mg metal electrodes with the Mg-In alloy, the nucleation of Mg dendrites is suppressed and instead the Mg electroalloys into the surface alloy upon reduction, significantly increasing the cell life time. Next, the Li-intercalation material LiTiS\u2082 is studied for use in organic reductive electrosynthesis as counter anodes. Traditional metal sacrificial counter anodes are known to cause issues such as surface passivation, chemical reactivity, and cross-plating at the working electrode, which is deleterious to the desired organic reactivity. It is found that LiTiS\u2082 surface is less reactive in organic electrolytes, reducing both passivation and chemical reactivity. Further, Li\u207a de-intercalated from LiTiS\u2082 oxidation is found to be less susceptible to cross-plating than Zn, a common sacrificial anode. Finally, the effect of electrode material on the electrochemical reduction of \u1d57BuI is studied. Using electrochemical characterization, it is found that the reduction is catalyzed on Au and Ag through adsorption of the initial substrate, as well as the adsorption of the reactive intermediate tBu radical. The catalysis of \u1d57BuI reduction can have meaningful consequences for organic reactivity, driving the desirable generation of the carbanion nucleophile from alkyl halide reactants.", "doi": "10.7907/fz2d-pe37", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:17264", "collection": "thesis", "collection_id": "17264", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05222025-165729471", "primary_object_url": { "basename": "pham_kim_2024_thesis-final.pdf", "content": "final", "filesize": 41860246, "license": "other", "mime_type": "application/pdf", "url": "/17264/1/pham_kim_2024_thesis-final.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Application of Ultrafast Spectroscopy Techniques to Probe Correlated Ion Hopping Mechanisms in Solid-State Ion Conductors", "author": [ { "family_name": "Pham", "given_name": "Kim Hoang", "orcid": "0000-0003-4053-6363", "clpid": "Pham-Kim-Hoang" } ], "thesis_advisor": [ { "family_name": "Cushing", "given_name": "Scott K.", "orcid": "0000-0003-3538-2259", "clpid": "Cushing-Scott-K" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "thesis_committee": [ { "family_name": "Blake", "given_name": "Geoffrey A.", "orcid": "0000-0003-0787-1610", "clpid": "Blake-G-A" }, { "family_name": "Stoltz", "given_name": "Brian M.", "orcid": "0000-0001-9837-1528", "clpid": "Stoltz-B-M" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Cushing", "given_name": "Scott K.", "orcid": "0000-0003-3538-2259", "clpid": "Cushing-Scott-K" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Superionic conductors, or solid-state ion conductors that surpass the ionic con- ductivity of its liquid counterpart, can enable more energy dense batteries, robust artificial ion pumps, and optimized fuel cells. The mechanisms enabling superionic conductivity still remain elusive, though many-body correlations between the mi- grating ions, lattice vibrational modes, and charge screening clouds have all been posited to greatly enhance ionic conduction. Most spectroscopic techniques cannot directly probe and validate the role of such correlations due to their inability to transiently resolve these ultrafast dynamics occurring at picosecond timescales. In this work, we develop an ultrafast technique that measures the time-resolved change in impedance while a light source ranging from UV to THz frequencies selectively excites an ion-coupled correlation. The technique is used to compare the relative changes in impedance of a solid-state Li\u207a conductor Li0.5La0.5TiO3 (LLTO) before and after light excitation to elucidate the role of charge screening clouds, optical phonons, and acoustic phonons on ion migration. From our techniques, we deter- mine that electronic screening and rocking phonon-mode interactions significantly dominate the ion migration pathway of LLTO compared to acoustic phonons. Al- though we only present one case study, our technique can extend to O\u00b2\u207b, H\u207a, or other charge carrier transport phenomena where ultrafast correlations control transport. Furthermore, the temporal relaxation of the measured impedance can distinguish ion transport effects caused by many-body correlations, optical heating, correlation, and memory behavior.", "doi": "10.7907/825x-r459", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:16680", "collection": "thesis", "collection_id": "16680", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08282024-022514845", "primary_object_url": { "basename": "Bruch_Dorian_2025.pdf", "content": "final", "filesize": 11174069, "license": "other", "mime_type": "application/pdf", "url": "/16680/1/Bruch_Dorian_2025.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Theoretical Modeling of Interactions Between Electrolytes and Surfaces", "author": [ { "family_name": "Bruch", "given_name": "Dorian Wayne", "orcid": "0000-0002-3983-4841", "clpid": "Bruch-Dorian-Wayne" } ], "thesis_advisor": [ { "family_name": "Wang", "given_name": "Zhen-Gang", "orcid": "0000-0002-3361-6114", "clpid": "Wang-Zhen-Gang" } ], "thesis_committee": [ { "family_name": "Brady", "given_name": "John F.", "orcid": "0000-0001-5817-9128", "clpid": "Brady-J-F" }, { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Wang", "given_name": "Zhen-Gang", "orcid": "0000-0002-3361-6114", "clpid": "Wang-Zhen-Gang" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Electrolytes are ubiquitous in science and engineering and are of active interest, owing to their applications biology, energy storage, colloidal suspensions, and even climate. Near a surface, electrolyte solutions exhibit a plethora of rich thermodynamic and structural phenomena, owing to the interplay of long-ranged electrostatics and nonelectrostatic interactions between ionic species, solvent, and the surface. In this thesis, we present a pedagogical formulation for the thermodynamics of electrolyte solutions near charged surfaces, followed by an examination of interactions and structure of different types of electrolytes near surfaces. Specifically, we investigate the difference between constant surface charge and constant surface potential boundaries in electrolyte solutions, the capacitance applications, double-layer structure, and screening behavior of a zwitterionic polymers, as well as the effect of image charge on structure, capacitance, and forces in simple electrolytes near metal, dielectric, and dielectrically-saturated metal surfaces. We conclude with a Gaussian-fluctuation model for ions with soft-core excluded volume interactions.", "doi": "10.7907/eey8-et93", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:16593", "collection": "thesis", "collection_id": "16593", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:07262024-075858049", "primary_object_url": { "basename": "ye_benjamin_2025_thesis.pdf", "content": "final", "filesize": 44395146, "license": "other", "mime_type": "application/pdf", "url": "/16593/3/ye_benjamin_2025_thesis.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Image Charge Effects Near Solid Surfaces", "author": [ { "family_name": "Ye", "given_name": "Benjamin Bobin", "orcid": "0000-0003-0253-6311", "clpid": "Ye-Benjamin-Bobin" } ], "thesis_advisor": [ { "family_name": "Wang", "given_name": "Zhen-Gang", "orcid": "0000-0002-3361-6114", "clpid": "Wang-Zhen-Gang" } ], "thesis_committee": [ { "family_name": "Giapis", "given_name": "Konstantinos P.", "orcid": "0000-0002-7393-298X", "clpid": "Giapis-K-P" }, { "family_name": "Brady", "given_name": "John F.", "orcid": "0000-0001-5817-9128", "clpid": "Brady-J-F" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Wang", "given_name": "Zhen-Gang", "orcid": "0000-0002-3361-6114", "clpid": "Wang-Zhen-Gang" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Ion\u2013surface interactions underpin fundamental biological and technological processes and hold the key to advancing the performance of modern electrochemical devices, such as electric double-layer capacitors (EDLCs). As such, a comprehensive understanding of the mechanistic details governing these interactions and their effects on the electrical double layer structure and charge transport is crucial. However, accurately modeling ion\u2013surface interactions in theory and simulations remains challenging due to the complexities and computational cost associated with properly treating dielectric discontinuities at ion\u2013surface interfaces. This thesis leverages the efficient method of image charges in coarse-grained molecular dynamics simulations to capture the correct behavior at the ion\u2013surface interface and unravel anomalous phenomena in various charged soft matter systems with conductive metal surfaces. Specifically, we construct a molecular model to demonstrate a spontaneous symmetry breaking transition in room-temperature ionic liquid EDLCs that provides a molecular mechanism for a hysteresis in the capacitance behavior observed experimentally. We also introduce a physically motivated soft-core model, the Gaussian core model with smeared electrostatics (GCMe), which addresses the limitations of traditional hard-core force fields in representing bulky organic ions and their spread charges, while also being orders of magnitude faster. Using GCMe, we then characterize the effects of the polyelectrolyte chain length, electrolyte polarizability, and electrode material on the energy storage of polymerized ionic liquid EDLCs, and the ion adsorption behavior and charging/discharging dynamics in polyelectrolyte EDLCs. Finally, we present MDCraft, an open-source Python assistant designed to streamline computational research workflows by providing tools for simulation setup, data analysis, and visualization. This comprehensive study not only enhances the understanding of ion-surface interactions but also offers practical insights and tools for advancing the design and optimization of systems involving charged species near surfaces, such as next-generation electrochemical energy storage devices.", "doi": "10.7907/fjpq-wn07", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:16457", "collection": "thesis", "collection_id": "16457", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06012024-040012207", "type": "thesis", "title": "Freeze-Cast Porous Ceramics: Tailoring Chemistry and Porosity for Functionality", "author": [ { "family_name": "Quinn", "given_name": "Laura Katherine", "orcid": "0000-0002-6112-028X", "clpid": "Quinn-Laura-Katherine" } ], "thesis_advisor": [ { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "thesis_committee": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "Kornfield", "given_name": "Julia A.", "orcid": "0000-0001-6746-8634", "clpid": "Kornfield-J-A" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Porous ceramics have been created and utilized in applications ranging from the automotive industry to biomedical research, with the chemical and pore characteristics of these ceramic structures crucial to their function and design. In this work, these intertwined factors are explored for a variety of applications by controlling the chemistry through precursor preparation and heat treatments, and the porosity controlled through freeze casting, a tunable and facile pore-forming technique yielding a range of pore sizes and morphologies. First, shape memory and superelastic behaviors in ceria-doped zirconia are observed by creating porous honeycomb structures that can accommodate the volume change of the martensitic transformation enabling such performance. By controlling dopant concentration, powder morphology, and freezing rate, the martensitic transformation is tracked over multiple cycles and collection volumes in these bulk-scale, polycrystalline zirconia ceramics. Next, transparent porous model sediments are created through heat treatments of freeze-cast synthetic cryolite (Na3AlF6) powder. Fluorescent beads the same size as many bacterial cells are visualized in a range of pore morphologies over both depth and time, and these porous ceramics are deployed in a sedimentary environment and the imaging of the microbial communities contained within and are found to colonize the porous cryolite structures. Alternate porous habitats for bacterial colonization are further created using materials such as iron oxides and carbon nanotubes to produce structures that can act both as electron acceptors and as microbial habitats. Finally, thermally anisotropic Si-based porous ceramics are developed with a potential use in optical devices. Using two contrasting preceramic polymers and both traditional and UV-assisted freeze-casting techniques, porous SiOC is produced from preceramic polymers with differing carbon contents. Together, these examples explore how the chemistry and porosity of porous ceramics can be manipulated to affect the chemical, optical, mechanical, and thermal properties of ceramic structures to best suit the intended function.", "doi": "10.7907/nj6y-4315", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16440", "collection": "thesis", "collection_id": "16440", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05302024-015407649", "primary_object_url": { "basename": "Zachery_Iton_Caltech_Thesis_2024_V2.pdf", "content": "final", "filesize": 56370845, "license": "other", "mime_type": "application/pdf", "url": "/16440/1/Zachery_Iton_Caltech_Thesis_2024_V2.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Superionic Conduction of Next-Generation Mobile Ions in Solids Enabled by Coordinating Ligands", "author": [ { "family_name": "Iton", "given_name": "Zachery William Benjamin", "orcid": "https://orcid.org/0000-0002-2226-9006", "clpid": "Iton-Zachery-William-Benjamin" } ], "thesis_advisor": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "thesis_committee": [ { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" }, { "family_name": "Greer", "given_name": "Julia R.", "orcid": "0000-0002-9675-1508", "clpid": "Greer-J-R" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Advancements in battery technologies are a critical step towards meeting the growing demand for sustainable energy storage solutions. The development of next-generation battery technologies using \"beyond-Li\" ions, like Na\u207a, K\u207a, Mg\u00b2\u207a, Ca\u00b2\u207a, Zn\u00b2\u207a, and Al\u00b3\u207a, could potentially offer improved performance, safety, and cost-effectiveness over traditional lithium-ion systems. However, the realization of next-generation battery technology based on \"beyond-Li\" mobile ions is limited, in part, due to a lack of understanding of solid state conduction of next-generation ions, which governs ion transport in electrodes, interphases, and solid electrolytes. \u201cBeyond-Li\u201d ions tend to have relatively low mobility in solids due to: (1) the larger ionic radii (Na\u207a, K\u207a, Ca\u00b2\u207a), which limit the accessible migration pathways, or (2) higher charge densities (Mg\u00b2\u207a, Zn\u00b2\u207a Al\u00b3\u207a), which results in strong electrostatic interactions within the solid.
\r\n \r\nThis work discusses several structure-property relationships and structural modifications that are hypothesized to lead to facile conduction of next-generation working ions. A notable discovery is the superionic conductivity of ZnPS3 after exposure to humid environments. Water is introduced into the grain boundaries, thereby enabling Zn\u00b2\u207a ions from the material to migrate and conduct freely in the network of adsorbed water. The introduction of water leads to potential H\u207a, therefore a methodology for decoupling the contributions of Zn\u00b2\u207a and H\u207a in mixed ionic conducting solids using ion-selective EIS, transference number measurements, and deposition experiments is established.
\r\n \r\nFurther extending this approach, superionic conductivity of other next-generation ions in electronically-insulating inorganic solids is achieved by leveraging the established ion exchange/intercalation mechanism of MPS3 (M = Cd, Mn) materials. The mobile cations that are introduced are coordinated with H2O ligands which simultaneously increase the size of the bottlenecks within the migration pathway and screen the charge-dense ions resulting in high mobilities. Potential applications can be extended to water-incompatible systems by replacing the water ligands with aprotic molecules.
\r\n \r\nThese insights contribute significantly to the understanding and development of next-generation battery technologies, representing an important step toward the development of more sustainable and efficient energy storage solutions.
", "doi": "10.7907/fwyd-2w86", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16356", "collection": "thesis", "collection_id": "16356", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04162024-184348195", "primary_object_url": { "basename": "Sun_Yuchun_2024.pdf", "content": "final", "filesize": 59124352, "license": "other", "mime_type": "application/pdf", "url": "/16356/230/Sun_Yuchun_2024.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "3D Micro-Architected Materials for Batteries", "author": [ { "family_name": "Sun", "given_name": "Yuchun", "orcid": "0000-0002-7028-3523", "clpid": "Sun-Yuchun" } ], "thesis_advisor": [ { "family_name": "Greer", "given_name": "Julia R.", "orcid": "0000-0002-9675-1508", "clpid": "Greer-J-R" } ], "thesis_committee": [ { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "West", "given_name": "William C.", "orcid": "0000-0001-6417-8930", "clpid": "West-W-C" }, { "family_name": "Greer", "given_name": "Julia R.", "orcid": "0000-0002-9675-1508", "clpid": "Greer-J-R" } ], "local_group": [ { "literal": "Resnick Sustainability Institute" }, { "literal": "div_eng" } ], "abstract": "Additive manufacturing (AM) enables three-dimensional micro-patterning of battery electrode materials, permitting complex structural designs beyond those of traditional slurry electrodes. We demonstrate two novel AM approaches for architecting electrode materials in lithium-ion batteries. First, we introduce a process for fabricating 3D micro-architected cathodes utilizing gel infusion additive manufacturing, and demonstrate this technique with lithium cobalt oxide (LCO). This method combines VP-based 3D printing with subsequent ion infusion and calcination processes. It starts with the printing of a blank organogel structure using a customized acrylate-based photoresin. This organogel is then converted into a hydrogel, infused with lithium and cobalt precursors, and finally subjected to calcination to form the LCO structure. This technique achieves 3D micro-architected LCO lattices with beam diameters of 45 \u03bcm, and maintains the designed architecture with tunable microstructures. By fabricating 3D micro-architected LiNi0.33Mn0.33Co0.33O2 (NMC111) through a very similar process, we demonstrate the potential for this gel infusion additive manufacturing method to engineer a variety of cathode materials for lithium-ion batteries in 3D.
\r\n\r\nWe also develop a fabrication method to create 3D lithium anodes supported by micro-architected carbon scaffold. By pyrolyzing 3D printed polymer microlattices, mechanically robust carbon electrodes are produced. Their micro-scale features and flexible structural control make them suitable as scaffolds for lithium-metal anodes. Surface functionalization and lithium electrodeposition are explored for dense lithium nucleation and uniform epitaxial growth on the carbon framework, resulting in micro-architected lithium/carbon anodes. With the rapid development of high-resolution AM techniques in recent decades, these approaches to additively manufacture cathode and anode materials provide promising pathways to build batteries with customizable 3D designs, and pursue higher energy and power densities for different applications.
", "doi": "10.7907/y6bt-xb40", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16151", "collection": "thesis", "collection_id": "16151", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08032023-213853772", "primary_object_url": { "basename": "Hickam_Bryce_2023.pdf", "content": "final", "filesize": 28267294, "license": "other", "mime_type": "application/pdf", "url": "/16151/1/Hickam_Bryce_2023.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Exploring How Entangled Photon Correlations Can Enhance Spectroscopy", "author": [ { "family_name": "Hickam", "given_name": "Bryce Patrick", "orcid": "0000-0003-2120-4769", "clpid": "Hickam-Bryce-Patrick" } ], "thesis_advisor": [ { "family_name": "Cushing", "given_name": "Scott K.", "orcid": "0000-0003-3538-2259", "clpid": "Cushing-Scott-K" } ], "thesis_committee": [ { "family_name": "Hadt", "given_name": "Ryan G.", "orcid": "0000-0001-6026-1358", "clpid": "Hadt-Ryan-G" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Blake", "given_name": "Geoffrey A.", "orcid": "0000-0003-0787-1610", "clpid": "Blake-G-A" }, { "family_name": "Cushing", "given_name": "Scott K.", "orcid": "0000-0003-3538-2259", "clpid": "Cushing-Scott-K" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Quantum light sources consisting of highly correlated or \"entangled\" photon pairs are increasingly becoming popular alternatives to classical light sources to perform microscopy and spectroscopy. Entangled photon pairs can replicate and enhance spectroscopic signals and have practical advantages compared to the pulsed laser systems that are typically utilized to perform these measurements. For instance, entangled photons are inherently low-flux, enabling measurements to be performed without undesired photoeffects, such as sample heating and degredation or nonideal photoinduced sample behavior. In addition, entangled photon sources can be generated and manipulated on much smaller physical footprints than state-of-the-art pulsed laser systems with comparable frequency bandwidths and time resolutions. Together, these capabilities could allow for the development of spectroscopic instruments that do not rely on bulky, expensive pulsed laser systems that necessitate teams of specialists to maintain. In turn, this instrument development could enable more widespread access to exotic forms of atomic and material characterization.
\r\n\r\nDespite a growing body of theoretical work, the field of experimental entangled photon spectroscopy is still nascent and entangled light-matter interactions have yet to be fully characterized in laboratory settings. Here, we investigate entangled photon light-matter interactions towards the goal of developing entangled spectroscopic techniques. A broadband entangled photon source with femtosecond coherence times is designed and characterized to perform these measurements. Using this source and an entangled photon spectrometer, characterization of the entangled photon enhancement to two-photon absorption are attempted by in studies of two different molecular dyes, Rhodamine 6G and zinc tetraphenylporphyrin. The entangled photon two-photon absorption enhancement is determined to be below previously reported values due to the presence of single photon scattering signals. Finally, entangled photons are utilized to replicate fluorescence lifetime measurements using a continuous wave pump laser and the temporal correlations inherent to entangled photon pairs. As the first experimental demonstration of this technique, the fluorescence lifetimes of indocyanine green in three solvent systems are measured.
", "doi": "10.7907/ez5h-qp07", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16161", "collection": "thesis", "collection_id": "16161", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08212023-202451948", "primary_object_url": { "basename": "Zhang_Caltech_Thesis_Final.pdf", "content": "final", "filesize": 45557113, "license": "other", "mime_type": "application/pdf", "url": "/16161/1/Zhang_Caltech_Thesis_Final.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Efforts Towards C-C Bond Formations: From Ni Catalysis to Transition-Metal Free Electrolysis", "author": [ { "family_name": "Zhang", "given_name": "Wanji Wendy", "orcid": "0000-0002-6895-9598", "clpid": "Zhang-Wanji-Wendy" } ], "thesis_advisor": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "thesis_committee": [ { "family_name": "Reisman", "given_name": "Sarah E.", "orcid": "0000-0001-8244-9300", "clpid": "Reisman-S-E" }, { "family_name": "Stoltz", "given_name": "Brian M.", "orcid": "0000-0001-9837-1528", "clpid": "Stoltz-B-M" }, { "family_name": "Fu", "given_name": "Gregory C.", "orcid": "0000-0002-0927-680X", "clpid": "Fu-G-C" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The selective construction of C-C bonds has been a critical challenge in modern synthetic organic chemistry. Among the numerous methodologies developed, cross-coupling remains an attractive strategy for direct C-C bond formation. Herein, a diverse range of cross-coupling reactions for C-C bond formations are investigated from different perspectives. First, the mechanism of a Ni/cyano-box-catalyzed asymmetric Suzuki alkynylation is studied. The existing data is consistent with a radical chain pathway that is previously proposed for other Ni-catalyzed enantioselective cross-coupling reactions. Next, moving on from the traditional electrophile-nucleophile cross-couplings, we explore Ni-catalyzed reductive coupling of alkyl halides with internal olefins in the presence of a hydrosilane. With judicious choice of the directing group, hydroalkylation of internal olefins can be achieved with high regio- and enantioselectivity. Following that, an electrochemically driven, transition-metal free cross-electrophile coupling reaction is explored as a greener alternative to constructive C(sp\u00b3)-C(sp\u00b3) bonds. Specifically, we focus on improving the Mg sacrificial anode performance in these electroreductive systems. By carefully choosing the electrolyte composition, we are able to manipulate the metal electrode interfaces for a more effective counter electrode. Finally, Al stripping in ethereal solvents is investigated for its application as a sacrificial anode in reductive electrosynthesis. Inspired by Al corrosion chemistry, we are able to achieve bulk Al stripping in THF-based electrolyte by incorporating halide co-supporting electrolytes.
", "doi": "10.7907/czam-9x35", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16364", "collection": "thesis", "collection_id": "16364", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04292024-194607461", "primary_object_url": { "basename": "Allison Stanko PhD Thesis FINAL.pdf", "content": "final", "filesize": 20735784, "license": "other", "mime_type": "application/pdf", "url": "/16364/1/Allison Stanko PhD Thesis FINAL.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Assembly of Complex Carbocyclic Architectures via Palladium and Nickel-Catalyzed Cyclizations", "author": [ { "family_name": "Stanko", "given_name": "Allison Michelle", "orcid": "0000-0003-0576-3739", "clpid": "Stanko-Allison-Michelle" } ], "thesis_advisor": [ { "family_name": "Stoltz", "given_name": "Brian M.", "orcid": "0000-0001-9837-1528", "clpid": "Stoltz-B-M" } ], "thesis_committee": [ { "family_name": "Nelson", "given_name": "Hosea M.", "orcid": "0000-0002-4666-2793", "clpid": "Nelson-H-M" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Reisman", "given_name": "Sarah E.", "orcid": "0000-0001-8244-9300", "clpid": "Reisman-S-E" }, { "family_name": "Stoltz", "given_name": "Brian M.", "orcid": "0000-0001-9837-1528", "clpid": "Stoltz-B-M" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Transition metal catalysis can be leveraged to construct challenging chemical bonds with excellent chemo- and stereoselectivity. Herein we describe the discovery of a novel palladium-catalyzed cascade cyclization and a nickel-catalyzed spirocyclization, enabling the assembly of complex carbocyclic architectures. We begin with an introduction describing notable applications of palladium-catalyzed cascade cyclizations in natural product synthesis, enabling the concurrent formation of C\u2013C and C\u2013N bonds in a single synthetic step.
\r\n\r\nNext, the development of a palladium-catalyzed oxidative Heck/aza-Wacker cascade cyclization is described. This cascade reaction enabled the construction of an all-carbon quaternary center, a C\u2013C bond, and a C\u2013N bond in a single synthetic step. Furthermore, it was employed to build the carbocyclic core of the natural product noraugustamine.
\r\n\r\nThen, we outline the discovery and optimization of an enantioselective nickel-catalyzed \u03b1-spirocyclization of lactones. The established method efficiently and enantioselectively forges 5-, 6-, and 7-membered rings containing all-carbon quaternary centers. This discovery represents an expansion of the synthetic toolkit for enantioselective spirocyclization, providing access to chiral, pharmaceutically relevant spirocyclic products.
\r\n\r\nFinally, we describe a collaborative project with the Su lab at the University of Arizona in the area of polymer synthesis and gas sensing, where we designed a sensor for the selective detection of gaseous nitric oxide. The sensor\u2019s excellent specificity and part-per-trillion level sensitivity was enabled by novel ferrocene-containing polymeric coatings.
", "doi": "10.7907/xx1b-9262", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16395", "collection": "thesis", "collection_id": "16395", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05202024-184723401", "primary_object_url": { "basename": "John Matthew Evans Thesis-Proofed_completed_final.pdf", "content": "final", "filesize": 8906764, "license": "other", "mime_type": "application/pdf", "url": "/16395/1/John Matthew Evans Thesis-Proofed_completed_final.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Impact of Interfacial Chemistry on Corrosion, Sensing, and Catalytic Properties of Materials", "author": [ { "family_name": "Evans", "given_name": "John Matthew", "orcid": "0000-0002-8721-5316", "clpid": "Evans-John-Matthew" } ], "thesis_advisor": [ { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" } ], "thesis_committee": [ { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Blake", "given_name": "Geoffrey A.", "orcid": "0000-0003-0787-1610", "clpid": "Blake-G-A" }, { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Interfaces are critical for the development of new technologies spanning applications from energy to sensing. Here, electrochemical and spectroscopic investigations of interfacial chemistry reveal how the sensitivity of chemical vapor sensors can be tuned, how stoichiometry and electrolysis affect the chemical state of a Mn-based oxygen evolution catalyst, and how the presence of barrier protection layers affects the stability of photoanodes in alkaline solution. Additionally, an in-depth discussion of x-ray photoelectron spectroscopy gives advice and insight into this surface-sensitive technique and several practical examples are discussed.", "doi": "10.7907/e033-xj27", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16190", "collection": "thesis", "collection_id": "16190", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09272023-154324412", "type": "thesis", "title": "Organic Films at the Electrode-Electrolyte Interface in CO\u2082 Reduction", "author": [ { "family_name": "Watkins", "given_name": "Nicholas Bret", "orcid": "0000-0001-7251-9387", "clpid": "Watkins-Nicholas-Bret" } ], "thesis_advisor": [ { "family_name": "Peters", "given_name": "Jonas C.", "orcid": "0000-0002-6610-4414", "clpid": "Peters-J-C" }, { "family_name": "Gregoire", "given_name": "John M.", "orcid": "0000-0002-2863-5265", "clpid": "Gregoire-J-M" } ], "thesis_committee": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Reisman", "given_name": "Sarah E.", "orcid": "0000-0001-8244-9300", "clpid": "Reisman-S-E" }, { "family_name": "Manthiram", "given_name": "Karthish", "orcid": "0000-0001-9260-3391", "clpid": "Manthiram-Karthish" }, { "family_name": "Peters", "given_name": "Jonas C.", "orcid": "0000-0002-6610-4414", "clpid": "Peters-J-C" }, { "family_name": "Gregoire", "given_name": "John M.", "orcid": "0000-0002-2863-5265", "clpid": "Gregoire-J-M" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This thesis focuses on the use of use high-throughput experimentation and analytical electrochemistry techniques to understand how organic films on (photo)electrode surfaces alter catalyst selectivity. Specifically, the objective has been to deconvolute effects associated with the organic film from the atomic identity of the catalyst, reactant and intermediate concentration polarization effects, and temperature in the context of electrochemical CO\u2082 reduction. The first chapter provides the motivations behind the transformation of CO\u2082 into value-added materials using electricity and the challenges that the field faces. The second chapter introduces the data-driven identification of a scaling relationship between the partial current densities of methane and C\u2082\u208a products among 14 bulk copper bimetallic alloys. This strict dependence represents an intrinsic limitation of selectivity tuning through alloying. However, it can be disrupted to favor C\u2082\u208a products by the presence of an organic additive, highlighting the potential of hybrid organic\u2013inorganic catalysts to tune branching ratios in the CO\u2082R reaction network. The third chapter highlights that with the wide band gap CuGa\u2083Se\u2085 chalcopyrite absorber, organic coatings can not only provide dramatic increases in selectivity toward CO\u2082R products compared to the unmodified system, but also and significantly moderate catalyst corrosion. The fourth chapter unveils a new class of molecular films on polycrystalline copper, derived from aryl diazonium and iodonium salts, that are corrosion resistant even at pH 1 and have the potential for many future electrochemical applications. In the fifth chapter, we demonstrate that increased mass transport at the electrode surface directly resulted in changes to the ethylene and methane Tafel slope values on copper electrodes. These findings emphasize that the apparent Tafel slope reported for any copper system is not necessarily representative of the catalyst\u2019s intrinsic kinetics alone, but also contains information about the cell geometry and electrolyte convective transport. The final chapter investigates the combined effect of organic films, mass transport, and electrode heating on electrocatalysis. We find that we can use surface heating to replace bulk heating, but that the complexity of CO\u2082R prevents predictable behavior. However, the addition of additive films to the electrode surface enables idealized electrochemical CO\u2082 reduction kinetics, and therefore the calculation of important parameters such as the activation energy for C\u2082\u208a product formation.", "doi": "10.7907/7t8e-7j20", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16375", "collection": "thesis", "collection_id": "16375", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05082024-165921385", "type": "thesis", "title": "Measuring Charge Carrier and Structural Photodynamics at Solar Energy Material Surfaces Using Transient Extreme Ultraviolet Reflection Spectroscopy", "author": [ { "family_name": "Michelsen", "given_name": "Jonathan Malte Zschiegner", "orcid": "0000-0002-7420-5610", "clpid": "Michelsen-Jonathan-Malte-Zschiegner" } ], "thesis_advisor": [ { "family_name": "Cushing", "given_name": "Scott K.", "orcid": "0000-0003-3538-2259", "clpid": "Cushing-Scott-K" } ], "thesis_committee": [ { "family_name": "Blake", "given_name": "Geoffrey A.", "orcid": "0000-0003-0787-1610", "clpid": "Blake-G-A" }, { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Cushing", "given_name": "Scott K.", "orcid": "0000-0003-3538-2259", "clpid": "Cushing-Scott-K" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Electronic and vibrational degrees of freedom, and their interactions, control the chemical and physical properties of solids. Core-level spectroscopies, such as transient extreme ultraviolet (XUV) spectroscopy, provide detailed information on the electronic structure and local coordination environment of a material. In this work, we employ transient XUV reflection spectroscopy to measure surface carrier and structural dynamics in solar energy materials. To interpret experimental spectra, excited state valence effects are incorporated into the OCEAN code (Obtaining core excitations from ab initio electronic structure and the NIST Bethe-Salpeter equation solver). The modeling of core-level spectra from first principles enables the extraction of carrier kinetics via the robust assignment of spectral features. Moreover, this thesis explores experimental and theoretical methods for understanding carrier-structural coupling in solids relevant to solar energy applications.
\r\n\r\nSpecifically, we explore the chemical and physical information contained in core-level spectra for various solar energy material systems and present guiding principles for designing a core-level electronic spectroscopy experiments to determine photoexcited carrier and structural dynamics. We report on experimental measurements of ultrafast surface carrier and structural dynamics in photocathodes zinc telluride and copper iron oxide. Further, complementary excited state theory is presented to extract excited state valence dynamics from experimental core-level spectra based on ground state implementations of the Bethe-Salpeter equation.
", "doi": "10.7907/73h7-kg35", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16267", "collection": "thesis", "collection_id": "16267", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12152023-235139391", "primary_object_url": { "basename": "Ware_thesis_final.pdf", "content": "final", "filesize": 24589417, "license": "other", "mime_type": "application/pdf", "url": "/16267/1/Ware_thesis_final.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "Nonaqueous Electrolyte Design for Energy Storage and Electrosynthesis", "author": [ { "family_name": "Ware", "given_name": "Skyler Danielle", "orcid": "0000-0002-3249-1946", "clpid": "Ware-Skyler-Danielle" } ], "thesis_advisor": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "thesis_committee": [ { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" }, { "family_name": "Cushing", "given_name": "Scott K.", "orcid": "0000-0003-3538-2259", "clpid": "Cushing-Scott-K" }, { "family_name": "Reisman", "given_name": "Sarah E.", "orcid": "0000-0001-8244-9300", "clpid": "Reisman-S-E" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "local_group": [ { "literal": "3MT Competition (Caltech)" }, { "literal": "div_chem" } ], "abstract": "Electrochemically driven metal redox has enabled advances in both academic and industrial processes, including production of metals from their ores, storage of renewable energy in batteries and fuel cells, and greener chemical synthesis conditions. While many electrochemical reactions are performed in aqueous solutions, applications in energy storage and organic synthesis often require extreme applied potentials that lie outside the electrochemical stability window of water or necessitate water-free conditions to prevent undesirable side reactions. Herein, we develop tailored non-aqueous electrolytes for applications in both energy storage and organic electrosynthesis and analyze the effects of electrolyte composition on interfacial and electrochemical reactions. First, a series of highly concentrated solvate electrolytes is developed for Li-S batteries, and interfacial reactivity between the solvate electrolytes and the Li anode is investigated in detail. The addition of a fluoroether cosolvent limits electrolyte decomposition at the Li surface, improving cycling stability and enabling new high-temperature applications. Next, samarium(III)/(II) redox is investigated in a variety of non-aqueous electrolytes to support an electrocatalytic cycle for samarium-mediated carbon-carbon bond formation. The coordination environment of the samarium salt, which can be tuned through anion exchange between the electrolyte and the samarium precursor, strongly affects the reversibility and reducing power of the samarium redox couple. Third, electrolyte additives are studied to increase the desolvation barrier of Zn\u00b2\u207a. When Zn sacrificial anodes are used in organic electrosynthesis, such additives may prevent deleterious cross-plating of Zn\u00b2\u207a at the cathode. Finally, a detailed guide to troubleshooting metal sacrificial anodes is presented with special attention to issues commonly encountered in reductive electrosynthesis.", "doi": "10.7907/kx7f-2065", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:15080", "collection": "thesis", "collection_id": "15080", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12282022-061839565", "type": "thesis", "title": "Electronic Structure and Reactivity of Metal Complexes", "author": [ { "family_name": "Barth", "given_name": "Alexandra Teresa", "orcid": "0000-0002-1813-4029", "clpid": "Barth-Alexandra-Teresa" } ], "thesis_advisor": [ { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" } ], "thesis_committee": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "Okumura", "given_name": "Mitchio", "orcid": "0000-0001-6874-1137", "clpid": "Okumura-M" }, { "family_name": "Cushing", "given_name": "Scott K.", "orcid": "0000-0003-3538-2259", "clpid": "Cushing-Scott-K" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Transition metals are at the core of addressing global energy needs. Functioning as catalysts, these systems have long demonstrated competency to promote thermodynamically challenging reactions, lowering energetic barriers and facilitating desired transformations with applied light or potential. Employing infrared, visible, ultraviolet, and x-ray spectroscopy, chemists are afforded insight into the electronic structures of transition metal complexes, investigating ligand field strengths and metal-ligand interactions. Addition of time-resolved techniques affords resolution of dynamic processes in molecular species, such as electron transfer pathways.
\r\n\r\nChapter 1 reviews the electronic structure and reactivity of homoleptic tungsten(0) arylisocyanides W(CNAr)\u2086 to provide the foundation for much of this work.
\r\n\r\nIn Chapter 2, application of W(CNAr)\u2086 species for one- and two-photon photoredox catalysis are explored. The two-photon absorption cross-sections of W(CNAr)\u2086 are remarkably large (\u03b4\u2088\u2081\u2080 = 180\u20131900 GM) and enable these photocatalysts to operate under excitation from visible or near infrared light. Photoredox activity is evaluated via base-promoted homolytic aromatic substitution (BHAS) reaction of thermodynamically challenging substrates. In Chapter 3, solvent perturbations enhance visible light-activated BHAS catalysis from W(CNAr)\u2086. Increased solvent dielectric (benzene to 1,2-difluorobenzene) and solvated electrolyte combine to increase *W(CNAr)\u2086 quenching rates up to one order of magnitude with greater cage-escape yields.
\r\n\r\nIn Chapter 4, the electronic structure of linear gold(I) arylisocyanide complexes ([Au(CNDipp-R)\u2082]\u207a; CNDipp = 2,6-diisopropylphenylisocyanide) are assigned using insights from UV-visible spectroscopy and time-dependent density functional theory (TD-DFT) calculations. In Chapter 5, the electronic structure of Fe(II) and Co(II) quaterpyridine photo-/electro-catalysts for CO\u2082 reduction are evaluated using UV-visible-NIR, \u00b9H NMR, M\u00f6ssbauer, and infrared spectra. Assignment of the absorption transitions are supported by TD-DFT calculations.
", "doi": "10.7907/k66v-1c93", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:15182", "collection": "thesis", "collection_id": "15182", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05162023-233932300", "primary_object_url": { "basename": "balzerThesis.pdf", "content": "final", "filesize": 17705659, "license": "other", "mime_type": "application/pdf", "url": "/15182/1/balzerThesis.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Polyelectrolytes Near Solid Surfaces", "author": [ { "family_name": "Balzer", "given_name": "Christopher James", "orcid": "0000-0002-9767-8437", "clpid": "Balzer-Christopher-James-J" } ], "thesis_advisor": [ { "family_name": "Wang", "given_name": "Zhen-Gang", "orcid": "0000-0002-3361-6114", "clpid": "Wang-Zhen-Gang" } ], "thesis_committee": [ { "family_name": "Brady", "given_name": "John F.", "orcid": "0000-0001-5817-9128", "clpid": "Brady-J-F" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Frischknecht", "given_name": "Amalie L.", "orcid": "0000-0003-2112-2587", "clpid": "Frischknecht-Amalie-L" }, { "family_name": "Wang", "given_name": "Zhen-Gang", "orcid": "0000-0002-3361-6114", "clpid": "Wang-Zhen-Gang" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Polyelectrolytes are ubiquitous in nature and in the products we use daily. The combination of their connectivity and charge lead to many useful properties in solution and near surfaces. Electrostatic forces dominate much of the behavior of charged species near solid surfaces; however, nonelectrostatic forces arising ion specific interactions or from varying polymer chemistry play an important role in tuning electrolyte and polyelectrolyte properties. The balance of these forces depends on factors like the salt concentration, solution pH, and properties of the surface. The current work outlines the thermodynamics of charged systems and investigates the structure and phase behavior of polyelectrolytes near solid surfaces. In particular, the work covers the thermodynamic aspects of preferential adsorption of small ions in electric double layers, polyelectrolyte adsorption, polymer-mediated interactions of surfaces using strong and weak electrolytes, surface phase transitions and contact angles of complex coacervates on solid surfaces, complexation-induced conformational phase transitions of polyelectrolyte brushes, and electro-swelling of weak polyelectrolyte brushes. The wide variety of problems addressed here reflects the variety of applications of polyelectrolytes and contexts in which polyelectrolytes appear.
", "doi": "10.7907/kga2-1820", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:15279", "collection": "thesis", "collection_id": "15279", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06022023-055053747", "type": "thesis", "title": "Complex Charge Compensation Mechanisms in Lithium-Rich Chalcogenide Cathodes", "author": [ { "family_name": "Zak", "given_name": "Joshua Joseph", "orcid": "0000-0003-3793-7254", "clpid": "Zak-Joshua-Joseph" } ], "thesis_advisor": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "thesis_committee": [ { "family_name": "Cushing", "given_name": "Scott K.", "orcid": "0000-0003-3538-2259", "clpid": "Cushing-Scott-K" }, { "family_name": "Giapis", "given_name": "Konstantinos P.", "orcid": "0000-0002-7393-298X", "clpid": "Giapis-K-P" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Hadt", "given_name": "Ryan G.", "orcid": "0000-0001-6026-1358", "clpid": "Hadt-Ryan-G" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Lithium-ion batteries have revolutionized the world by enabling long-lasting portable electronics, electrified transportation, and grid storage solutions for renewable energy implementation. However, current commercialized technologies are limited by the one electron transfer per transition metal paradigm utilized by cathode materials that operate with an intercalation-based charge storage mechanism. Finding ways to increase the charge storage capabilities of the cathode into the multielectron regime has long been a focus of research efforts, and involvement of structural anions in the redox has been demonstrated as a promising way to accomplish multielectron storage. Layered lithium-rich oxide materials have been shown to afford dramatic improvements to overall storage capacity but are plagued by complex mechanisms and unwanted side reactions that lead to poor cycling stability and characterization difficulties. This thesis expands upon previous understanding of oxide-based anion redox materials and extends the exploration into sulfide and selenide systems, which allow the study of anion redox without the side processes that affect oxides. First, a dynamic charge compensation mechanism of late group metal-poor, lithium-rich oxide, Li2Ru0.3Mn0.7O3, is uncovered and found to involve an irreversible anion oxidation that leads to involvement of redox states on transition metals previously thought to be unavailable. Second, active electrolyte additives are explored as a method of stabilizing the cathode-electrolyte interface of anion redox material, Li2RuO3. Third, reversible anion redox is demonstrated in alkali-rich sulfides, Li2FeS2 and LiNaFeS2, and proven to occur through oxidation of sulfides (S2-) to persulfides ([S2]2-). Understanding of the structural ramifications of anion oxidation in Li2FeS2 is further expanded through computational and experimental methods. Fourth, the role of metal-anion covalency is systematically investigated through anion substitution of Li2FeS2 with S2-, highlighting the importance of a holistic understanding of changes to the electronic and physical structure of anion redox materials to predict long-term performance. Finally, detailed perspectives and future outlooks on sulfur redox in lithium battery systems are offered with an exhaustive survey of thermodynamically stable binary and ternary persulfide materials.
", "doi": "10.7907/1k50-3811", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:15115", "collection": "thesis", "collection_id": "15115", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03062023-153330120", "primary_object_url": { "basename": "Heng_thesis_Mar2022.pdf", "content": "final", "filesize": 3962819, "license": "other", "mime_type": "application/pdf", "url": "/15115/1/Heng_thesis_Mar2022.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Optimization of Electrodes Towards More Practical Electrochemical Water Treatment", "author": [ { "family_name": "Dong", "given_name": "Heng", "orcid": "0000-0002-4168-7297", "clpid": "Dong-Heng" } ], "thesis_advisor": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" } ], "thesis_committee": [ { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Wennberg", "given_name": "Paul O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Due to water scarcity and water pollution, the world suffers from continuing water sanitation issues, which lead to billions of water-borne disease cases every year. Decentralized water treatment is regarded as an important supplement to the conventional wastewater treatment system to address the water sanitation and water pollution issues in rural, remote, and undeveloped regions. Electrochemical water treatment technology has been demonstrated to be feasible for decentralized water treatment systems because of the ambient operation conditions, robust performance, modular design, small footprint, and environmental compatibility. The performance of electrochemical water treatment systems relies heavily on the choice of electrodes. This thesis presents a comprehensive study towards understanding and optimizing the electrodes to enhance the performance and lower the cost of electrochemical water treatment systems. The research work on anodes followed an \u201cunderstanding \u2013 development\u201d approach and spanned both the scientific and engineering sides of the spectrum. Specifically, a comprehensive review was assembled through the analysis of existing literature on mixed metal oxide anodes. This review pointed towards potential future research directions. With the advancement of material sciences, it is important to focus not only on single catalytic metal elements, but also on the intermetallic electronic interaction to gain a deeper understanding of the catalytic activity of mixed metal oxides. The microscopic steric effects imposed by crystalline structures may also be a nonnegligible contributor to the catalytic properties.
\r\n\r\nFollowing the review, this thesis scrutinized the catalytic sites of crystalline CoSb\u2082O\u2086, an emerging anode for chlorine evolution reaction (CER) catalysis. It has been demonstrated to be a promising alternative for the conventional Ru- and Ir-based anodes based on its high activity and excellent stability, but its catalytic sites and mechanism are still unknown. By fabricating and testing a series of anodes with different Sb/Co ratios, it was discovered that the surface Sb/Co ratios in CoSb\u2082O\u2086 were ~50% higher than in the bulk. At the same time, it was surprising to find through scanning electrochemical microscopy (SECM) that Sb-rich samples showed higher catalytic activities, indicating that Sb sites may be even more active catalytic sites than the Co-sites. This was attributed to the electronic interaction between Co and Sb, as revealed by X-ray photoelectron spectroscopy (XPS).
\r\n\r\nOn the engineering side, a Ni\u2013Sb\u2013SnO\u2082 reactive electrochemical membrane (REM) was developed to treat primary effluent and greywater. In 30 min, the REM removed up to 78 \u00b1 2% COD and 94 \u00b1 0.6% turbidity from the primary effluent. The REM had ~100% COD removal and 89 \u00b1 4% turbidity removal from greywater, with the effluent meeting the NSF/ANSI 350 standard. Compared to the conventional plate-type electrodes under the same conditions, the REM had 36% lower energy consumption for primary effluent treatment and 22% lower energy consumption for greywater treatment while yielding better treatment results. The REM-based electrochemical system was demonstrated to be a promising solution for decentralized wastewater treatment and recycling for single households and for vehicles.
\r\n\r\nLast but not the least, this thesis presents the 3D-printing-derived carbon lattice as a monolithic electro-Fenton cathode. The Fenton reaction is one of the most important advanced oxidation processes (AOPs) that is widely used in water treatment to remove non-biodegradable pollutants, and heterogeneous electro-Fenton (HEF) process catalyzed by carbon-based cathodes has received considerable attention as an evolving branch due to its wide working pH range and independence from chemical dosing. However, the conventional carbon cathodes suffered from poorly controlled porosities, which hampered the mass transport and limited the overall catalytic performance. Three rationally-designed carbon lattice cathodes with different macroscopic porosities were fabricated and tested, showing that it was feasible to facilitate the mass transport by tuning the macroscopic electrode structure. Specifically, Grid-2% cathode, which had the largest macroscopic porosity, showed 157% higher specific activity for electrochemical H\u2082O\u2082 production and 256% higher specific activity for trimethoprim degradation than the Star-2%, the one with the smallest macroscopic porosity. Grid-2% achieved 97% aqueous trimethoprim removal in 60 min, demonstrating the potential of the carbon lattice cathode to be used for water treatment and remediation.
", "doi": "10.7907/hkpg-je79", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:15118", "collection": "thesis", "collection_id": "15118", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03132023-113800696", "primary_object_url": { "basename": "Yi_Zhang_Thesis_Final.pdf", "content": "final", "filesize": 5182026, "license": "other", "mime_type": "application/pdf", "url": "/15118/2/Yi_Zhang_Thesis_Final.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Application of Heterojunction Ni-Sb-SnO\u2082 Anodes for Electrochemical Water Treatment", "author": [ { "family_name": "Zhang", "given_name": "Yi", "orcid": "0000-0002-9062-5201", "clpid": "Zhang-Yi" } ], "thesis_advisor": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" } ], "thesis_committee": [ { "family_name": "Sessions", "given_name": "Alex L.", "orcid": "0000-0001-6120-2763", "clpid": "Sessions-A-L" }, { "family_name": "Frankenberg", "given_name": "Christian", "orcid": "0000-0002-0546-5857", "clpid": "Frankenberg-Christian" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Gschwend", "given_name": "Philip M.", "orcid": "0000-0002-9497-4492", "clpid": "Gschwend-Philip-M" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" } ], "local_group": [ { "literal": "Resnick Sustainability Institute" }, { "literal": "div_gps" } ], "abstract": "Clean water supply and adequate sanitation services are critical for public health as well as for food production. Small-scale decentralized treatment represents an attractive alternative that can provide necessary water treatment in many parts of the developing world where centralized wastewater treatment facilities are not practical owing to financial, geographical, or political constraints. Electrochemical oxidation (EO) is a suitable technique for decentralized treatment settings since it does not require the addition of auxiliary chemicals and offers fast reaction kinetics and modular treatment capacity. EO is considered a versatile technology since it can degrade a wide array of contaminants and inactivate waterborne pathogens. The chemical composition of the anode, where EO takes place, is a key factor that controls reactive species production and thus treatment efficiency and energy consumption. Ideal anodes for wastewater treatment should have high overpotential for oxygen evolution (\u201cnonactive\u201d anodes) and favor complete organics oxidation through direct electron transfer and/or reactions with potent oxidants such as hydroxyl radical and ozone. Common nonactive anodes including antimony-doped tin oxide (Sb-SnO\u2082), lead oxide (PbO\u2082), and boron-doped diamond (BDD) have attracted wide research interests. The work presented in this thesis centered around a newly designed heterojunction Ni-Sb-SnO\u20822-based anode (NAT/AT) and its various applications in decentralized water and wastewater treatment. Direct treatment using NAT/AT has proved to be efficient for chemical oxygen demand removal, trace organic compound degradation, and microbial disinfection. Detailed investigation into pharmaceutical degradation kinetics and transformation products further established NAT/AT as a potential treatment alternative for the control of pharmaceuticals and their metabolites in hospital wastewaters. NAT/AT is also capable of synthesizing ferrates (e.g., FeO\u2084\u00b2\u207b) in circumneutral conditions, the high oxidation state iron species that represents another group of powerful oxidants well-suited for decentralized treatment purposes. In an additional effort to tackle high concentrations of ammonium often present in latrine wastewaters, functionalized metal-organic framework (MOF), a class of materials featuring high porosity, abundant active sites, and highly tunable physical and chemical properties, was used to recover the ammonium nitrogen. Various modifications of MOF-808, a highly water stable MOF, were designed and synthesized to achieve urea hydrolysis, ammonium capture, and real-time ammonium sensing in sequence. In combination, the described works provide a powerful toolkit that can be used in treating various waste streams before discharge and/or reuse.", "doi": "10.7907/dmrd-w489", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:16071", "collection": "thesis", "collection_id": "16071", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06032023-004803929", "primary_object_url": { "basename": "Steve_Kim_Thesis_compressed.pdf", "content": "final", "filesize": 4723734, "license": "other", "mime_type": "application/pdf", "url": "/16071/4/Steve_Kim_Thesis_compressed.pdf", "version": "v8.0.0" }, "type": "thesis", "title": "Design Rules for Multi-Electron Systems in Next-Generation Batteries: From Mg Electrode-Electrolyte Interface to Anion Redox Activation in Li-Rich Sulfides", "author": [ { "family_name": "Kim", "given_name": "Seong Shik (Steve)", "orcid": "0000-0003-2604-6392", "clpid": "Kim-Seong-Shik-Steve" } ], "thesis_advisor": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "thesis_committee": [ { "family_name": "Wang", "given_name": "Zhen-Gang", "orcid": "0000-0002-3361-6114", "clpid": "Wang-Zhen-Gang" }, { "family_name": "Brady", "given_name": "John F.", "orcid": "0000-0001-5817-9128", "clpid": "Brady-J-F" }, { "family_name": "Agapie", "given_name": "Theodor", "orcid": "0000-0002-9692-7614", "clpid": "Agapie-T" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Li-ion batteries (LIBs) have revolutionized the modern world, powering portable electronic devices and more recently realizing electrification of transportation. With more technological advancements that further improved the performance, LIBs also play an important role as one of the most promising energy storage systems in transforming into renewable energy sources and achieving net zero emissions. However, state-of-the-art intercalation-based LIBs are beginning to mature and reach their theoretical capacity limits. To further improve the electrochemical performance of batteries and meet growing demands of energy storage applications, there have been growing efforts to increase the energy density beyond the limits of conventional LIBs. In this thesis, we examine two examples of multi-electron systems\u2013Mg electrolytes and Li-rich sulfide cathode materials\u2013to gain insights and establish design principles.
\r\n\r\nFirst, we explore the magnesium aluminum chloride complex (MACC) electrolyte to study the role of the electrode-electrolyte interface in Mg charge transfer. We demonstrate that MACC electrolyte which normally requires electrolytic conditioning can be chemically activated by the small addition of Mg(HMDS)\u2082. Solution-phase characterization reveals that Mg(HMDS)\u2082 helps prevent the formation of passivating film on the Mg surface by scavenging trace amounts of H\u2082O. Mg(HMDS)\u2082 also reacts with MACC to form free Cl\u207b which decorates the Mg surface which facilitates Mg electrodeposition and stripping.
\r\n\r\nNext, we investigate three different alkali-rich sulfides-LiNaFeS\u2082, LiNaCoS\u2082, and Li1.33-1.33zTi0.67+0.33zVaczS\u2082 - to probe the role of electronic and physical structure in governing reversible anion redox. We demonstrate that cryomilling LiNaFeS\u2082 mitigates particle fracturing by increasing microstrain and reducing crystallite size. Isostructural LiNaCoS\u2082 exhibits more covalent interactions between the transition metal-d and S-p states compared to LiNaFeS\u2082, but undergoes an irreversible conversion reaction. Lastly, Li\u2082TiS\u2083 exhibits no electrochemical activity, but introducing cationic vacancies in Li1.33-1.33zTi0.67+0.33zVaczS\u2082 activates S oxidation. Li1.33-1.33zTi0.67+0.33zVaczS\u2082 is studied further to study first-cycle activation and voltage hysteresis in Li-rich sulfides.
", "doi": "10.7907/v52j-t589", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:16084", "collection": "thesis", "collection_id": "16084", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06052023-155701672", "type": "thesis", "title": "Development of Selective Carbon\u2013Carbon Bond-Forming Reactions of Vinyl Carbocations", "author": [ { "family_name": "Williams", "given_name": "Chloe Gabrielle", "orcid": "0000-0001-5090-8146", "clpid": "Williams-Chloe-Gabrielle" } ], "thesis_advisor": [ { "family_name": "Nelson", "given_name": "Hosea M.", "orcid": "0000-0002-4666-2793", "clpid": "Nelson-H-M" } ], "thesis_committee": [ { "family_name": "Stoltz", "given_name": "Brian M.", "orcid": "0000-0001-9837-1528", "clpid": "Stoltz-B-M" }, { "family_name": "Reisman", "given_name": "Sarah E.", "orcid": "0000-0001-8244-9300", "clpid": "Reisman-S-E" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Nelson", "given_name": "Hosea M.", "orcid": "0000-0002-4666-2793", "clpid": "Nelson-H-M" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Carbocationic intermediates play an important role in the construction of complex molecules, from biosynthetic pathways in nature to the synthesis of natural products by organic chemists. Herein, a brief introduction that surveys C\u2013C bond forming reactions of vinyl carbocations is highlighted. The discussion of experimental work commences with the development of a main group-catalyzed approach towards accessing vinylated esters through the trapping of vinyl carbocations with silyl ketene acetals. Next, a Claisen-type rearrangement is discussed, which is a result of trapping vinyl carbocations with allyl ethers to form an allyl vinyl oxonium intermediate in situ that can subsequently rearrange. Finally, the last method that is highlighted includes the development of an asymmetric C\u2013H insertion reaction of vinyl carbocations to forge bicyclic products in a highly enantioselective fashion.", "doi": "10.7907/rkge-pz74", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:14329", "collection": "thesis", "collection_id": "14329", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08202021-200738765", "type": "thesis", "title": "Molecular Simulations of Charge Transport for Energy Storage and Conversion Applications", "author": [ { "family_name": "Kim", "given_name": "Jeongmin", "orcid": "0000-0002-7405-8200", "clpid": "Jeongmin-Kim" } ], "thesis_advisor": [ { "family_name": "Miller", "given_name": "Thomas F.", "orcid": "0000-0002-1882-5380", "clpid": "Miller-T-F" } ], "thesis_committee": [ { "family_name": "Wang", "given_name": "Zhen-Gang", "orcid": "0000-0002-3361-6114", "clpid": "Wang-Zhen-Gang" }, { "family_name": "Miller", "given_name": "Thomas F.", "orcid": "0000-0002-1882-5380", "clpid": "Miller-T-F" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Jones", "given_name": "Simon C.", "orcid": "0000-0002-1952-3720", "clpid": "Jones-Simon-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Molecular simulation plays a variety of roles in accelerating the development of energy materials, from providing a fundamental understanding of molecular processes to predicting their performance spanning a wide range of chemical space. In this thesis, we present molecular simulation studies of charge transport both in bulk energy materials and at their interfaces to provide molecular principles for advanced rechargeable batteries in part I and electricity generation using a metal nanofilm from water motion in part II.
\r\n\r\nIn part I, we discuss ion transport and interfacial electron transfer in polymeric battery materials, both of which are closely associated with battery operation. As a bulk electrolyte and a solid electrolyte interphase (SEI), polymeric materials often benefit rechargeable batteries, allowing for enhanced safety and increased energy density. Firstly, we propose a unique mechanism of lithium-ion transport in polymer-based electrolytes, including conjugated polymers with an imidazolium sidechain and polyborane-based single-ion conductors, which utilizes the formation of a percolating ion network to facilitate lithium ion transport. Secondly, we discuss interfacial ion solvation structure and dynamics that are closely related to interfacial electron-transfer kinetics. Simulations provide molecular insights into how a functional SEI passivates a metal electrode, thereby accelerating materials discovery such as an artificial SEI of self-assembled monolayers.
\r\n\r\nIn part II, we present molecular principles of energy conversion from a flow of ionic solution to electricity using metal nanolayers. The energy conversion emerges at a water-solid interface and requires a boundary of an electrical double layer at which ion adsorption and desorption occur along with the flow. We discuss charge induction mechanisms related to a heterolayered structure of a metal nanolayer and investigate factors that affect energy conversion efficiency in two different modes of operation, namely a flow cell and a wavetank.
", "doi": "10.7907/5haz-ch54", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:14953", "collection": "thesis", "collection_id": "14953", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06062022-211326081", "primary_object_url": { "basename": "Saccone_Max_Thesis_2022.pdf", "content": "final", "filesize": 54345211, "license": "other", "mime_type": "application/pdf", "url": "/14953/1/Saccone_Max_Thesis_2022.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Vat Photopolymerization Additive Manufacturing of Functional Materials: from Batteries to Metals and Alloys", "author": [ { "family_name": "Saccone", "given_name": "Max Anthony", "orcid": "0000-0003-3846-2908", "clpid": "Saccone-Max-Anthony" } ], "thesis_advisor": [ { "family_name": "Greer", "given_name": "Julia R.", "orcid": "0000-0002-9675-1508", "clpid": "Greer-J-R" } ], "thesis_committee": [ { "family_name": "Manthiram", "given_name": "Karthish", "orcid": "0000-0001-9260-3391", "clpid": "Manthiram-Karthish" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Kornfield", "given_name": "Julia A.", "orcid": "0000-0001-6746-8634", "clpid": "Kornfield-J-A" }, { "family_name": "Greer", "given_name": "Julia R.", "orcid": "0000-0002-9675-1508", "clpid": "Greer-J-R" } ], "local_group": [ { "literal": "Resnick Sustainability Institute" }, { "literal": "div_chem" } ], "abstract": "In recent years, additive manufacturing (AM), also known as 3D printing, has emerged as a uniquely powerful tool for rapid prototyping and for creating complex, high value structures. Vat polymerization (VP) is an AM technique which forms parts through light-initiated polymerization, capable of achieving both high resolution and high throughput. While VP has been utilized to fabricate a wide variety of polymeric materials, fabricating functional materials such as ceramics, metals, and inorganic composites has remained a challenge. This thesis focuses on developing fabrication methods for a range of functional materials, from battery active materials to metals and ceramics, via vat polymerization additive manufacturing, taking advantage of chemical reactions within an AM part after fabrication to form target materials in situ.
\r\n\r\nWe demonstrate the use of emulsions to introduce aqueous active material precursors into organic photopolymer resins to create architected lithium sulfide/carbon composites for use as lithium-sulfur battery cathodes. Such architected cathode materials are promising for mitigating mechanical degradation in high volume-change battery materials such as the sulfur cathode. We additionally performed nanome- chanical experiments on lithium sulfide powders to determine how lithium sulfide yields, deforms, and fails in the context of volume-change-induced stress during battery cycling. Because lithium sulfide is present as a discharge product in all lithium sulfur batteries, these nanomechanical particle compressions have bearing on the entire field, beyond the realm of 3D architected cathodes.
\r\n\r\nWe additionally demonstrate the use of organogel templates to streamline the AM process by enabling the fabrication of many materials starting with a single resin composition, followed by infiltration of appropriate metal precursors and post-processing heat treatment to convert the polymer/precursor matrix to the target metal via calcination and reduction reactions. We fabricate and characterize copper, nickel, silver, cobalt, cupronickel alloys, tungsten, and more to highlight the wide-ranging versatility of achievable materials and microstructures.
", "doi": "10.7907/v3cn-8h28", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:14466", "collection": "thesis", "collection_id": "14466", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01042022-032834418", "primary_object_url": { "basename": "Mazza_Thesis_Final.pdf", "content": "final", "filesize": 14277889, "license": "other", "mime_type": "application/pdf", "url": "/14466/1/Mazza_Thesis_Final.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Defect-Driven Reactivity of Layered Materials Examined through Atomic Layer Deposition", "author": [ { "family_name": "Mazza", "given_name": "Michael Francis", "orcid": "0000-0003-3995-3100", "clpid": "Mazza-Michael-Francis" } ], "thesis_advisor": [ { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" } ], "thesis_committee": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Beauchamp", "given_name": "Jesse L.", "orcid": "0000-0001-8839-4822", "clpid": "Beauchamp-J-L" }, { "family_name": "Brunschwig", "given_name": "Bruce S.", "orcid": "0000-0002-6135-6727", "clpid": "Brunschwig-B-S" }, { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Layered materials are a unique class of materials that are characterized by strong covalent bonds in single layers in the two-dimensional plane, but much weaker van der Waals interactions between layers. This unique bonding environment gives rise to remarkable chemical and physical properties. These materials can be easily exfoliated into single atomic layers, true two-dimensional materials, or few-layer stacks. As the number of layers changes, the physical and chemical properties can be modified. Similarly, as the relative position of one or more layers is changed, this change in the bonding environment has substantial impacts on the properties. Due to their unique bonding environment, layered materials are unusually inert to atomic layer deposition. Atomic layer deposition (ALD) is a surface-sensitive deposition technique that relies on a sequence of chemical reactions on the surface of a substrate to deposit the target material. Using this surface-sensitive deposition technique, the crystal structure and chemical bonding environment of the layered material can be interrogated.
\r\n\r\nChapter 1 investigates the spontaneous formation of highly ordered triangular and linear pattern depositions on layered material substrates. These patterns form with two different layered material substrates and with two separate ALD reactions. The pattern depositions do not change with increasing deposition time or with different concentrations of reactants. These networks, while highly unusual to observe chemically, are discussed through a well-established dislocation theory, where defects in the crystal structure of layered materials can impact the surface reactivity.
\r\n\r\nChapter 2 explores the stacking order characteristics of few-layer materials and discusses how changing the stacking order can change the crystal structure and the electronic properties of the materials. The chapter describes the field of few-layer materials and the process of modifying or transferring nanoflakes to new substrates. The chapter introduces a new transfer system that allows for patterned nanoflakes with stacking fault networks to be transferred to new substrates with micron-scale precision. The crystal structure of both the deposited triangular networks and the layered material beneath is discussed.
\r\n\r\nChapter 3 describes a new approach to selectively targeting defect sites in monolayer graphene. A new, water-free atomic layer deposition chemistry is introduced to precisely react metal oxides with high-energy defect sites on graphene. The quality of the film is interrogated and the selectivity of the film is determined by measuring the thickness of the film deposited on the defect-rich regions. The results confirm that this ALD process creates a robust passivating film while keeping the unperturbed regions clean of any metal oxide.
", "doi": "10.7907/nnwh-5355", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:14420", "collection": "thesis", "collection_id": "14420", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11062021-151820825", "primary_object_url": { "basename": "Welch_thesis_final_8Dec2021.pdf", "content": "final", "filesize": 110423776, "license": "other", "mime_type": "application/pdf", "url": "/14420/5/Welch_thesis_final_8Dec2021.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Understanding and Optimizing the Local Catalyst Environment in CO\u2082 Reduction Electrodes", "author": [ { "family_name": "Welch", "given_name": "Alexandra Justine", "orcid": "0000-0003-2132-9617", "clpid": "Welch-Alexandra-Justine" } ], "thesis_advisor": [ { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" } ], "thesis_committee": [ { "family_name": "Greer", "given_name": "Julia R.", "orcid": "0000-0002-9675-1508", "clpid": "Greer-J-R" }, { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Understanding and managing the local microenvironments in carbon dioxide reduction catalysts is crucial for optimizing device performance. In particular a locally high pH can increase catalyst selectivity and activity, as well as indicate which part of the catalyst is most active. In this thesis we begin by studying how nanoporous catalysts can induce this locally high pH in an aqueous system. We observe an increase in both Faradaic efficiency and partial current density for carbon monoxide in the nanoporous system relative to a planar metal film. We then show that this same nanoporous architecture can be used for improved device performance in a gas diffusion electrode configuration. We also perform copper underpotential deposition and secondary ion mass spectroscopy to show that almost half of the catalyst is not in contact with the electrolyte in this configuration. Then we use confocal fluorescent microscopy to image the local pH in a gas diffusion electrode to determine which parts of the electrode are most active. Through a combination of experiment and simulations we find that the catalyst within thin cracks of the microporous layer is most active for carbon dioxide reduction. While the study of local pH and wetting is the main focus of this thesis, we also explore how light can be used to improve selectivity and activity. In particular we study gold nanoparticles on p-type gallium nitride and copper nanoparticles on p-type nickel oxide. Finally, this thesis also explores how carbon dioxide conversion can actually be deployed. We discuss opportunities for combining carbon dioxide capture and conversion, as well as evaluate different pathways for renewable methane generation.
\r\n\r\nThis thesis gives in depth analysis of electrochemical carbon dioxide reduction catalysts as well as putting this research into the larger context of how such devices can be deployed. We hope that by combining systems level thinking and specific device studies better carbon dioxide conversion systems can be realized.
", "doi": "10.7907/4s78-cq55", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:14563", "collection": "thesis", "collection_id": "14563", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04272022-163740814", "primary_object_url": { "basename": "DeLano_Thesis_Final.pdf", "content": "final", "filesize": 39397720, "license": "other", "mime_type": "application/pdf", "url": "/14563/1/DeLano_Thesis_Final.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Development of Nickel-Catalyzed Asymmetric Cross-Coupling Reactions", "author": [ { "family_name": "DeLano", "given_name": "Travis Jon", "orcid": "0000-0002-2052-611X", "clpid": "DeLano-Travis-Jon" } ], "thesis_advisor": [ { "family_name": "Reisman", "given_name": "Sarah E.", "orcid": "0000-0001-8244-9300", "clpid": "Reisman-S-E" } ], "thesis_committee": [ { "family_name": "Robb", "given_name": "Maxwell J.", "orcid": "0000-0002-0528-9857", "clpid": "Robb-M-J" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Stoltz", "given_name": "Brian M.", "orcid": "0000-0001-9837-1528", "clpid": "Stoltz-B-M" }, { "family_name": "Reisman", "given_name": "Sarah E.", "orcid": "0000-0001-8244-9300", "clpid": "Reisman-S-E" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Asymmetric cross-coupling reactions have emerged in recent decades as powerful tools for the formation of valuable carbon\u2013carbon bonds in the synthesis of enantioenriched small molecules. Nickel catalysis in particular has proven to be an especially powerful tool for the formation of C(sp\u00b2)\u2013C(sp\u00b3) bonds in part due to the propensity of nickel catalysts to access odd oxidation states and interact with radical intermediates. Application of asymmetric nickel catalysis to a variety of radical precursors has resulted in the development of a broad range of stereoconvergent reductive and redox-neutral cross coupling reactions, allowing for the highly enantioselective formation of many synthetically useful and biologically relevant molecules.
\r\n\r\nHerein we describe our recent efforts in the development of new nickel-catalyzed enantioselective cross-coupling reactions. First, an enantioselective reductive cross- coupling of alkenyl and benzyl halides was rendered electroreductive. Careful electrochemical cell design proved critical for this reaction, which represents the first report of an enantioselective nickel-catalyzed electroreductive cross coupling reaction. We next discuss our development of an enantioselective reductive cross coupling of \u237a-chloroesters with aryl iodides. This reaction proceeds with especially high ee when \u03b2-branched substrates are employed, prompting the development of a multivariate linear regression model to probe the origin of the observed enantioselectivity trends. Finally, a redox-neutral nickel/photoredox co-catalyzed coupling of \u237a-N-heterocyclic potassium alkyl trifluoroborates and aryl bromides is reported. This reaction, developed in collaboration with researchers at Merck, provides rapid enantioselective access to motifs commonly found in bioactive molecules.
", "doi": "10.7907/pzfp-ad90", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:14069", "collection": "thesis", "collection_id": "14069", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02012021-171503477", "primary_object_url": { "basename": "JacobBagley_ThesisPDF.pdf", "content": "final", "filesize": 11019676, "license": "other", "mime_type": "application/pdf", "url": "/14069/1/JacobBagley_ThesisPDF.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Fabrication of Pristine and Doped Graphene Nanostripes and their Application in Energy Storage", "author": [ { "family_name": "Bagley", "given_name": "Jacob David", "orcid": "0000-0001-9490-1341", "clpid": "Bagley-Jacob-David" } ], "thesis_advisor": [ { "family_name": "Yeh", "given_name": "Nai-Chang", "orcid": "0000-0002-1826-419X", "clpid": "Yeh-Nai-Chang" } ], "thesis_committee": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Yeh", "given_name": "Nai-Chang", "orcid": "0000-0002-1826-419X", "clpid": "Yeh-Nai-Chang" }, { "family_name": "Cushing", "given_name": "Scott K.", "orcid": "0000-0003-3538-2259", "clpid": "Cushing-Scott-K" }, { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Fossil fuel usage causing rising CO2 levels and leading to climate change is, perhaps, the most pressing issue of our time. However, our economic dependence on energy necessitates its usage such that reducing energy usage is not possible leaving transitioning to renewable energy technologies as the only sustainable option. Currently, the largest barrier to large scale incorporation of renewable energy sources (e.g., solar, wind) is the high cost of energy storage technologies. Electrochemical energy storage technologies (e.g., lithium-ion batteries and supercapacitors) have been identified as a key approach for enabling the transition to renewable energy technologies.
\r\n\r\nGraphene is a material with exceptional properties that is receiving much attention for application in various energy storage technologies and could help reduce the cost of energy storage technologies. This thesis describes a novel fabrication procedure for low-cost and efficient synthesis of high-quality graphene nanostripes (GNSPs) and their application in lithium-ion battery and supercapacitor electrodes.
\r\n\r\nThis thesis is structured as follows. Chapter 1 outlines the motivation and technical background of this research. Chapter 2 describes the instrumentation and procedures for fabricating GNSPs. Chapter 3 describes in situ exfoliation of GNSPs as electrodes in supercapacitors to increase the capacitance. Chapter 4 describes synthesis and application of pyridinic-type nitrogen-doped GNSPs as a lithium-ion battery anode. Chapter 5 describes the synthesis and application of silicon-, germanium-, and tin-doped GNSPs and their application in lithium-ion battery anodes. Chapter 6 concludes and synthesizes the findings of the thesis holistically. Additionally, future outlook and potential research objectives are presented.
", "doi": "10.7907/hfdw-fs13", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:14131", "collection": "thesis", "collection_id": "14131", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05012021-183915976", "primary_object_url": { "basename": "Narita_Kai_2021.pdf", "content": "final", "filesize": 9041369, "license": "other", "mime_type": "application/pdf", "url": "/14131/28/Narita_Kai_2021.pdf", "version": "v8.0.0" }, "type": "thesis", "title": "3D Architected Battery Electrodes for Exploring Battery Kinetics from Nano to Millimeter", "author": [ { "family_name": "Narita", "given_name": "Kai", "orcid": "0000-0002-3867-8234", "clpid": "Narita-Kai" } ], "thesis_advisor": [ { "family_name": "Greer", "given_name": "Julia R.", "orcid": "0000-0002-9675-1508", "clpid": "Greer-J-R" } ], "thesis_committee": [ { "family_name": "Bhattacharya", "given_name": "Kaushik", "orcid": "0000-0003-2908-5469", "clpid": "Bhattacharya-K" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Greer", "given_name": "Julia R.", "orcid": "0000-0002-9675-1508", "clpid": "Greer-J-R" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The ability to design a particular geometry of porous electrodes at multiple length scales in a lithium-ion battery can significantly and positively influence battery performance because it enables control over kinetics and trajectories of ion and electron transport. None of the existing methods of engineering electrode structure is capable of creating 3D architected electrodes designed with independent and flexible form-factors at multiscale that are also resilient against cell packaging pressure. In addition, battery kinetics coupled at multiscale from ion transport in an electrolyte to solid electrolyte interphase (SEI) growth has only been studied by numerical simulations, but has never been experimentally explored.
\r\n\r\nIn this thesis, we demonstrate an additive manufacturing technique to engineer porous electrode structure in 3D and explore battery kinetics at multiscale. First, we develop 3D architected carbon electrodes, whose structural factors are independently controlled and whose dimensions span microns to centimeters, using digital light processing and pyrolysis.\r\nThese free-standing lattice electrodes are disordered graphitic carbon composed of several stacked graphitic layers that are mechanically robust. Galvanostatic cycling using these architected carbon electrodes showed sloping capacity, typically observed in pyrolyzed carbon electrodes. We discuss the modified rate performance of the 3D architected carbon electrodes in the framework of ion transport kinetics in the electrode vs. electrolyte and overpotential, enabled by controlling structural factors of battery electrodes, including porosity, surface morphology, electrode thickness, and beam diameter, whose length scales range from nano to millimeter.
\r\n\r\nWe then explore battery kinetics associated with SEI using deterministic, mechanically resilient, and thick 3D architected carbon electrodes, which allow us to study the formation, structure-resistance relationship, and position-dependent growth of SEI by combining the newly developed in operando DC-based technique and post-characterization using secondary ion mass spectroscopy. The amount of Li in SEI agrees with capacity losses, and the amount of F in SEI showed a strong linear correlation with SEI resistance evolutions. The position-dependent SEI growth was experimentally explored; the Li amount in SEI along the electrode thickness agrees with the simulation results in prior work, but the F amount in SEI showed the opposite tendency, suggesting modeling of multilayer SEI is necessary to predict precisely battery aging especially for thick electrodes. Our work demonstrates the use of 3D architected electrodes as a model system to explore multiscale kinetics in Li-ion batteries.
", "doi": "10.7907/dr3b-2d27", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:14171", "collection": "thesis", "collection_id": "14171", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05242021-164534392", "type": "thesis", "title": "Experimental and Theoretical Investigation of a Reductant-Activated Methodology for Covalent Functionalization of 1T' Transition Metal Dichalcogenides MoS\u2082 and WS\u2082", "author": [ { "family_name": "Yan", "given_name": "Ellen", "orcid": "0000-0003-3252-790X", "clpid": "Yan-Ellen" } ], "thesis_advisor": [ { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" } ], "thesis_committee": [ { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" }, { "family_name": "Wennberg", "given_name": "Paul O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Chemically exfoliated MoS\u2082 (ceMoS\u2082) is a two-dimensional layered transition metal dichalcogenide in the 1T' phase that can be synthesized by intercalating and exfoliating MoS\u2082 of the thermodynamically stable and relatively inert 2H phase. Several functionalization techniques have emerged in the past decade to functionalize both the 2H and 1T' phases, with growing interest given the array of applications for MoS\u2082 in optoelectronics, catalysis, sensing, bioimaging, drug delivery, and photothermal treatment. To aid in this effort, we expanded upon a recently reported covalent functionalization method by developing a reduction-activated methodology to functionalize ceMoS\u2082 using one-electron metallocenes and showed that the coverage of a functional group increases as the reduction potential increases, allowing for greater control of the coverage. Using density functional theory (DFT), we found that the coverage of the smallest functional group, a methyl, is expected to be limited to ~64% per MoS\u2082 due to the steric hinderance associated with the methylation of sulfur sites that are adjacent to more than one methyl group. We also found that a similar coverage trend can be observed when applying reduction-activated functionalization to ceWS\u2082, albeit with a lower coverage at every potential that can be explained using DFT calculations as a difference in the thermodynamic favorability of the reaction. Reductant-activated functionalization provides a driving force that enables ceMoS\u2082 and 2H-MoS\u2082 to be functionalized when it is otherwise unreactive with electrophiles. Conceptualizing the work herein as part of a redox-activated functionalization method, there is an abundance of opportunity to explore oxidant- and reductant-activated functionalization on other chalcogenides, pnictides, and materials in the carbon and boron groups using both solution oxidants and reductants, as well as electrode-based electrochemical methods. Further exploration of redox-activated techniques expands the functionalization toolbox and enables researchers to develop application-specific functional materials.
", "doi": "10.7907/gcjw-bb78", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:14107", "collection": "thesis", "collection_id": "14107", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03172021-221106133", "primary_object_url": { "basename": "202104_Weilai_Thesis_Final.pdf", "content": "final", "filesize": 24982845, "license": "other", "mime_type": "application/pdf", "url": "/14107/1/202104_Weilai_Thesis_Final.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "Stability of Photo-Electrochemical Interface for Solar Fuels", "author": [ { "family_name": "Yu", "given_name": "Weilai", "orcid": "0000-0002-9420-0702", "clpid": "Yu-Weilai" } ], "thesis_advisor": [ { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" } ], "thesis_committee": [ { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Okumura", "given_name": "Mitchio", "orcid": "0000-0001-6874-1137", "clpid": "Okumura-M" } ], "local_group": [ { "literal": "Resnick Sustainability Institute" }, { "literal": "Kavli Nanoscience Institute" }, { "literal": "JCAP" }, { "literal": "div_chem" } ], "abstract": "Photoelectrochemical (PEC) water splitting is a promising approach to convert renewable solar energy to clean hydrogen (H2) fuels in one simple step. Although \u2162-\u2164 semiconductors are attractive candidates as light-absorbers in tandem solar-fuel devices, their long-term stability for the hydrogen-evolution reaction (HER) in either acidic or alkaline aqueous electrolytes needs to be established. Chapter 2-5 of this thesis first aims at revealing the underlying corrosion chemistry for a variety of \u2162-\u2164 semiconductors specifically under the HER conditions, offering a rational understanding towards the stability of semiconductor photoelectrode.
\r\n \r\nIn Chapter 2, we start from p-InP and reveal its susceptibility to cathodic photocorrosion forming metallic In0, which however can be completely mitigated by the presence of Pt catalyst due to kinetic stabilization. We also show that the resulting PEC performance of p-InP/Pt electrodes is sensitive to the changes in surface stoichiometry, whereas an InOx-rich surface developed in KOH caused a substantial degradation in the current density-potential (J-E) behavior. In Chapter 3, we discovered that a non-stoichiometric and As0-rich surface of p-GaAs, resulting from a galvanic corrosion by Pt, led to mid-gap surface states as well as a complete loss in photoactivity. In Chapter 4-5, we demonstrate similar kinetic stabilization applied to both p-InGaP2/Pt and pn+-InGaP2/Pt photocathodes for the HER at both pH 0 and pH 14. Additionally, we found that the corrosion of underlying GaAs substrates for the pn+-InGaP2/Pt photocathodes at positive potentials caused damage of structural integrity as well as instability in electrode performance. Altogether these works underscore the mutual dependence of the physical and electrochemical stability of semiconductor photoelectrodes during the HER, which also need to be considered separately. Moreover, both catalytic kinetics and surface stoichiometry are crucial factors for defining long-term corrosion chemistry for semiconductor photoelectrode.
\r\n \r\nIn Chapter 6-7, we further explore solar fuels beyond H2, namely electrochemical N2-to-NH3 conversion. We first establish a new analytical method to isotopically quantify the concentrations of 15NH3 in aqueous solutions with a high sensitivity and a low limit-of-detection of <1 \u03bcM. Further we applied this advanced method to rigorously verify the electrocatalytic activity of a CoMo electrode for reducing N2(g) to NH3. We show that the additional ammonia detected in electrolyte was instead attributed to the corrosion of N impurities present in the CoMo electrode under cathodic bias, thus giving false positive results. These works emphasize the importance of both rigorous product analysis and experiment design in further catalyst development.
", "doi": "10.7907/2z16-d005", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:13577", "collection": "thesis", "collection_id": "13577", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11152019-095230239", "primary_object_url": { "basename": "DelCiello-Thesis-Full.pdf", "content": "final", "filesize": 2536431, "license": "other", "mime_type": "application/pdf", "url": "/13577/19/DelCiello-Thesis-Full.pdf", "version": "v8.0.0" }, "type": "thesis", "title": "Kinetic Studies of Hydrogen Oxidation by Cobaloximes and Synthesis, Spectroscopy and Boronation of a New Heteroleptic Ruthenium Cyanide Complex", "author": [ { "family_name": "Del Ciello", "given_name": "Sarah Anne", "orcid": "0000-0002-7571-8944", "clpid": "Del-Ciello-Sarah-Anne" } ], "thesis_advisor": [ { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" } ], "thesis_committee": [ { "family_name": "Reisman", "given_name": "Sarah E.", "orcid": "0000-0001-8244-9300", "clpid": "Reisman-S-E" }, { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "Peters", "given_name": "Jonas C.", "orcid": "0000-0002-6610-4414", "clpid": "Peters-J-C" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Cobaloximes are macrocyclic complexes well-studied as homogeneous catalysts for hydrogen evolution, but they are also competent at the microscopic reverse reaction, hydrogen oxidation. Kinetic studies of Co(dmgBF2)2L2 reacting with hydrogen and base reveal a rate law that is second-order in cobalt and first-order in H2, indicating that the mechanism of H-H bond breaking is homolytic.
\r\n\r\nThe reduction potentials of metal cyanide complexes can be tuned by appending boranes to the N-terminus. By boronating ruthenium cyanide complexes containing diimine ligands, the RuII/III couple can be tuned without drastic modification of the diimine0/- couple. A new member of the [Ru(dimmine)(CN)4]2- family is synthesized with the ligand 4,4\u2019-bis(trifluoromethyl)-2,2\u2019-bipyridine (CF3bpy) and boronated, resulting in a molecule with two reversible redox events separated by 3.2 V.
", "doi": "10.7907/6QTC-G360", "publication_date": "2020", "thesis_type": "phd", "thesis_year": "2020" }, { "id": "thesis:13795", "collection": "thesis", "collection_id": "13795", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06082020-143301441", "primary_object_url": { "basename": "New_Electrolytic_Media_and_Methods_for_Energy_Storage_and_Conversion.pdf", "content": "final", "filesize": 41742032, "license": "other", "mime_type": "application/pdf", "url": "/13795/1/New_Electrolytic_Media_and_Methods_for_Energy_Storage_and_Conversion.pdf", "version": "v8.0.0" }, "type": "thesis", "title": "New Electrolytic Media and Methods for Energy Storage and Conversion", "author": [ { "family_name": "McNicholas", "given_name": "Brendon James", "orcid": "0000-0002-3654-681X", "clpid": "McNicholas-Brendon-James" } ], "thesis_advisor": [ { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "Grubbs", "given_name": "Robert H.", "orcid": "0000-0002-0057-7817", "clpid": "Grubbs-R-H" } ], "thesis_committee": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "Grubbs", "given_name": "Robert H.", "orcid": "0000-0002-0057-7817", "clpid": "Grubbs-R-H" }, { "family_name": "Okumura", "given_name": "Mitchio", "orcid": "0000-0001-6874-1137", "clpid": "Okumura-M" }, { "family_name": "Winkler", "given_name": "Jay Richmond", "orcid": "0000-0002-4453-9716", "clpid": "Winkler-J-R" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "New electrolytic media and methods for energy storage and conversion are needed to fully realize the sustained use of renewable energy and complete removal of dependence on fossil fuels. Motivated by this urgency, researchers today are heavily invested in developing new electrocatalytic systems for carbon dioxide sequestration to reduce greenhouse gas emissions and new battery architectures, such as non-aqueous redox flow batteries, to keep solar energy at our disposal during peak times of energy consumption. Chapter 1 provides an overview of the conceptual frameworks for these two alternative energy technologies and a literature review of relevant work and inspiration in these fields. Chapter 2 demonstrates one of the first examples of ionic liquid voltammetry of a molecular species, namely (tpfc)Mn, and its electron transfer reactivity in ionic liquids with varying solvent viscosity, effective electrolyte concentration, and donor strength. As well as showing the non-unity diffusional properties of molecular species in ionic liquids and the capability of ionic liquid anions to coordinate to molecular species, these studies suggest the viability of ionic liquids as conductive media for energy storage and conversion. Chapter 3 introduces methods for immobilization of molecular catalysts in polymeric ion gels, a general strategy that bridges the divide between homogeneous solution-state catalysis and heterogeneous solid-state catalysis. These results provide insight into how environment, catalyst concentration, catalyst mobility, substrate availability, and dielectric properties of a medium all affect the catalytic response and overpotential for CO2 reduction. Further implementation of these ion gel composites in solid-state devices, in aqueous environments, and in gas diffusion electrodes is also discussed. In Chapter 4, a brief overview of the use of boranes as capping ligands for cyanide is provided. The synthesis, electronic properties, and theoretical calculations of homoleptic, boronated Fe(II) hexacyanoferrates are reported. Addition of borane to cyanometallates dramatically alters electronic structures and is a novel method for permanent modification of formal potentials while simultaneously maintaining or improving electrochemical reversibility and ambient stability. These complexes are characterized and studied by cyclic and differential pulse voltammetry, UV-vis, IR, and Raman spectroscopy, and flash-quench photolysis. Chapter 5 extends the unique reactivity of borane adducts to the characterization of a full series of hexaisocyanoboratometallates (Cr, Mn, Fe, Ru, Os), compounds which demonstrate the concept of cyanide as a \u201cvariable-field\u201d ligand, including magnetic circular dichroism spectroscopy, electron paramagnetic resonance spectroscopy, luminescence studies, excited-state lifetime studies, and electrochemistry. As electrolytes for non-aqueous redox flow batteries, these species exhibit excellent Coulombic and voltage efficiencies and fast electron transfer rates. The highly oxidizing species will also find use as reversible oxidants for chemical oxidations. Chapter 6 extends the concept of modifying formal potentials to heteroleptic cyanometallates (M = Fe, Ru) with diimine ligands (L = bipyridine, phenanthroline, 4,4\u2019-trifluoromethylbipyridine). These species are shown to be potent excited-state reductants and oxidants, strong and long-lived phosphors, and promising electrolytes for symmetric, non-aqueous redox flow batteries. These data also demonstrate improved excited-state lifetimes for borane-appended species, likely due to inhibition of non-radiative decay pathways. Chapter 7 focuses on the generation of a solution stable, square pyramidal Co(II) species, which is studied by electrochemistry, UV-vis-NIR spectroscopy, X-band and Q-band CW EPR, and pulsed EPR techniques (HYSCORE, ENDOR). These studies demonstrate that boronation of cyanide differentially affects the energies of ligand field transitions based on \u03c0 backbonding ability.", "doi": "10.7907/1sew-r360", "publication_date": "2020", "thesis_type": "phd", "thesis_year": "2020" }, { "id": "thesis:11390", "collection": "thesis", "collection_id": "11390", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02112019-143327096", "primary_object_url": { "basename": "Weadock_Nicholas_2019_Final.pdf", "content": "final", "filesize": 25632235, "license": "other", "mime_type": "application/pdf", "url": "/11390/1/Weadock_Nicholas_2019_Final.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Addressing Thermodynamic Inefficiencies of Hydrogen Storage in Transition Metal Hydrides", "author": [ { "family_name": "Weadock", "given_name": "Nicholas Joseph", "orcid": "0000-0002-1178-7641", "clpid": "Weadock-Nicholas-Joseph" } ], "thesis_advisor": [ { "family_name": "Fultz", "given_name": "Brent T.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B-T" } ], "thesis_committee": [ { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Johnson", "given_name": "William Lewis", "clpid": "Johnson-W-L" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Fultz", "given_name": "Brent T.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B-T" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Transition metal hydrides (MH) are an attractive class of materials for several energy technologies. Primary benefits include their large volumetric storage capacity (often exceeding that of liquid hydrogen) and capability to absorb and desorb hydrogen for hundreds of cycles. In this thesis, we set out to understand two of the thermodynamic inefficiencies of MH: the pressure hysteresis associated with hydrogen absorption and desorption and the corrosion and dissolution of high capacity MH alloys in high pH electrolyte environments.
\r\n\r\nThe volume change associated with hydriding transitions can exceed 10%, and a macroscopic nucleation barrier resulting from coherency strains has been proposed as the origin of the pressure hysteresis. We investigated this hypothesis for the palladium-hydrogen system. The hysteresis and phase transformation characteristics of bulk and nanocrystalline PdH were characterized with coupled in situ X-ray diffraction and pressure composition isotherm measurements. Size effects are observed in the total hydrogen uptake and hydrogen solubility in the hydride phases. Experimentally determined hysteresis energies were found to be comparable to the misfit strain between the Pd and PdH phases and much larger than the energy for dislocation formation. Theoretical predictions of pressure hysteresis overestimate the experimentally measured hysteresis, and we suggest methods of accommodation which could explain the discrepancy. Finally, we propose that an effect of the nucleation barrier is to split the coherent spinodal phase diagram and introduce directionally dependent phase boundaries.
\r\n\r\nWe report a successful development of Ti29V62-xNi9Crx (x = 0, 6, 12) body-centered cubic (BCC) MH electrodes for MH batteries by addressing vanadium corrosion and dissolution in potassium hydroxide electrolytes. The effectiveness of a limited oxygen environment and vanadate ion addition against corrosion are compared to the effects of Cr substitution. By identifying oxygen as the primary source of corrosion and eliminating oxygen with an Ar-purged cell, the Cr-free alloy electrode achieved a maximum capacity of 594 mAh/g, double the capacity of commercial AB5 MH electrodes. With modified coin cells suppressing oxygen evolution, the cycle stability of the Ti29V62Ni9 alloy electrode was greatly improved with either vanadate ion additions to the electrolyte or Cr-substitution in the alloy. Both approaches lead to reversible capacity of 500 mAh/g for 200 cycles.
", "doi": "10.7907/ANY4-VA70", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:11685", "collection": "thesis", "collection_id": "11685", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06042019-235050436", "primary_object_url": { "basename": "Moreno-Hernandez_Ivan__Thesis_Final.pdf", "content": "final", "filesize": 10434518, "license": "other", "mime_type": "application/pdf", "url": "/11685/1/Moreno-Hernandez_Ivan__Thesis_Final.pdf", "version": "v8.0.0" }, "type": "thesis", "title": "Earth-Abundant Metal Oxides for Anodic Reactions in Acidic Electrolytes", "author": [ { "family_name": "Moreno-Hernandez", "given_name": "Ivan A.", "orcid": "0000-0001-6461-9214", "clpid": "Moreno-Hernandez-Ivan-A" } ], "thesis_advisor": [ { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" } ], "thesis_committee": [ { "family_name": "Okumura", "given_name": "Mitchio", "orcid": "0000-0001-6874-1137", "clpid": "Okumura-M" }, { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" }, { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "local_group": [ { "literal": "JCAP" }, { "literal": "div_chem" } ], "abstract": "The development of electrochemical systems such as electrolyzers and photoelectrochemical devices in corrosive electrolytes has been limited by the lack of earth-abundant materials that are both stable in acidic electrolytes and efficiently utilize energy for electrochemical reactions. Chapter 1 introduces several of the challenges in developing earth-abundant materials for electrochemical systems in acidic electrolytes, such as electrocatalysts for the oxygen and the chlorine evolution reactions, and protective layers for photoanodes. Chapter 2 reports the electrochemical behavior of crystalline transition metal antimonates consisting of solid solutions of MnSb2O6 with NiSb2O6 for the oxygen evolution reaction in strongly acidic electrolytes. In Chapter 3, the crystalline transition metal antimonates NiSb2O6, CoSb2O6, and MnSb2O6 are investigated for the chlorine evolution reaction, and CoSb2O6 is found to exhibit activity and stability comparable to noble metal oxide electrocatalysts. Chapter 4 describes the development of earth-abundant SnOx coatings as protective heterojunctions for planar Si photoanodes in corrosive electrolytes. Chapter 5 focuses on the development of conformal SnOx coatings that form protective heterojunctions on Si microcone photoanodes. The work presented herein demonstrates several strategies towards the development of stable earth-abundant materials for efficient electrochemical and photoelectrochemical energy conversion in acidic electrolytes.
", "doi": "10.7907/XRN5-FV98", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:11390", "collection": "thesis", "collection_id": "11390", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02112019-143327096", "primary_object_url": { "basename": "Weadock_Nicholas_2019_Final.pdf", "content": "final", "filesize": 25632235, "license": "other", "mime_type": "application/pdf", "url": "/11390/1/Weadock_Nicholas_2019_Final.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Addressing Thermodynamic Inefficiencies of Hydrogen Storage in Transition Metal Hydrides", "author": [ { "family_name": "Weadock", "given_name": "Nicholas Joseph", "orcid": "0000-0002-1178-7641", "clpid": "Weadock-Nicholas-Joseph" } ], "thesis_advisor": [ { "family_name": "Fultz", "given_name": "Brent T.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B-T" } ], "thesis_committee": [ { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Johnson", "given_name": "William Lewis", "clpid": "Johnson-W-L" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Fultz", "given_name": "Brent T.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B-T" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Transition metal hydrides (MH) are an attractive class of materials for several energy technologies. Primary benefits include their large volumetric storage capacity (often exceeding that of liquid hydrogen) and capability to absorb and desorb hydrogen for hundreds of cycles. In this thesis, we set out to understand two of the thermodynamic inefficiencies of MH: the pressure hysteresis associated with hydrogen absorption and desorption and the corrosion and dissolution of high capacity MH alloys in high pH electrolyte environments.
\r\n\r\nThe volume change associated with hydriding transitions can exceed 10%, and a macroscopic nucleation barrier resulting from coherency strains has been proposed as the origin of the pressure hysteresis. We investigated this hypothesis for the palladium-hydrogen system. The hysteresis and phase transformation characteristics of bulk and nanocrystalline PdH were characterized with coupled in situ X-ray diffraction and pressure composition isotherm measurements. Size effects are observed in the total hydrogen uptake and hydrogen solubility in the hydride phases. Experimentally determined hysteresis energies were found to be comparable to the misfit strain between the Pd and PdH phases and much larger than the energy for dislocation formation. Theoretical predictions of pressure hysteresis overestimate the experimentally measured hysteresis, and we suggest methods of accommodation which could explain the discrepancy. Finally, we propose that an effect of the nucleation barrier is to split the coherent spinodal phase diagram and introduce directionally dependent phase boundaries.
\r\n\r\nWe report a successful development of Ti29V62-xNi9Crx (x = 0, 6, 12) body-centered cubic (BCC) MH electrodes for MH batteries by addressing vanadium corrosion and dissolution in potassium hydroxide electrolytes. The effectiveness of a limited oxygen environment and vanadate ion addition against corrosion are compared to the effects of Cr substitution. By identifying oxygen as the primary source of corrosion and eliminating oxygen with an Ar-purged cell, the Cr-free alloy electrode achieved a maximum capacity of 594 mAh/g, double the capacity of commercial AB5 MH electrodes. With modified coin cells suppressing oxygen evolution, the cycle stability of the Ti29V62Ni9 alloy electrode was greatly improved with either vanadate ion additions to the electrolyte or Cr-substitution in the alloy. Both approaches lead to reversible capacity of 500 mAh/g for 200 cycles.
", "doi": "10.7907/ANY4-VA70", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:11493", "collection": "thesis", "collection_id": "11493", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05032019-105139564", "primary_object_url": { "basename": "Thompson-Caltech-Thesis-Final.pdf", "content": "final", "filesize": 5384155, "license": "other", "mime_type": "application/pdf", "url": "/11493/7/Thompson-Caltech-Thesis-Final.pdf", "version": "v14.0.0" }, "type": "thesis", "title": "Interfacial Behavior of 2D Materials in Devices for Solar Fuels and Sensing Applications", "author": [ { "family_name": "Thompson", "given_name": "Annelise C.", "orcid": "0000-0003-2414-7050", "clpid": "Thompson-Annelise-C" } ], "thesis_advisor": [ { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" } ], "thesis_committee": [ { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Okumura", "given_name": "Mitchio", "orcid": "0000-0001-6874-1137", "clpid": "Okumura-M" }, { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The field of 2D materials has expanded widely in the past 15 years to include many materials beyond graphene. However, the applications of graphene and its derivatives are still limited by the lack of thorough knowledge on how to successfully integrate a 2D material into a device while maintaining its unique properties. The work in this thesis investigates the application of 2D materials, such as graphene, fluorinated graphene, and hexagonal boron nitride, in solar fuels and sensing devices to reveal patterns that can inform device design with these and other materials in the future. In the second chapter, lightly fluorinated graphene is investigated as a protective layer on silicon photoanodes. This material is shown to possess superior abilities as a protective layer against oxidizing conditions as well as other deleterious surface reactions. The introduction of fluorine atoms to the lattice at postulated to terminate defects found along grain boundaries, leading to enhanced stability over 24h. The third chapter addresses the energetics of silicon/2D material/liquid junctions to elucidate how the density of states in these materials affect the formation of efficient charge-separation junctions. Hexagonal boron nitride on p-type silicon is shown to form a superior junction to graphene, as measured by changes in the open-circuit potential against a range of one-electron redox couples. Finally, chapter four shows the integration of a monolayer of graphene into a polymer-based chemiresistive vapor sensor to substantially enhance the signal of the sensor over the graphene or polymer alone. The response is dependent on strain at the graphene interface as demonstrated by Raman spectroscopy.
", "doi": "10.7907/DQF7-JD96", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:11037", "collection": "thesis", "collection_id": "11037", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06072018-140534228", "type": "thesis", "title": "Cathode Design for High Energy Molten Salt Lithium-Oxygen Batteries", "author": [ { "family_name": "Tozier", "given_name": "Dylan Douglas", "orcid": "0000-0001-9489-8824", "clpid": "Tozier-Dylan-Douglas" } ], "thesis_advisor": [ { "family_name": "Greer", "given_name": "Julia R.", "orcid": "0000-0002-9675-1508", "clpid": "Greer-J-R" } ], "thesis_committee": [ { "family_name": "Fultz", "given_name": "Brent T.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B-T" }, { "family_name": "Greer", "given_name": "Julia R.", "orcid": "0000-0002-9675-1508", "clpid": "Greer-J-R" }, { "family_name": "Johnson", "given_name": "William Lewis", "clpid": "Johnson-W-L" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "State of the art commercial lithium ion batteries use cathodes such as lithium cobalt oxide which rely on insertion and removal of lithium ions from a host material. However, insertion cathode materials are limited in their capacity, and replacing them with a cathode that employs growth and dissolution of new phases could significantly increase a battery\u2019s energy density. For example, oxygen and sulfur cathodes have been widely researched to this end, with both cases involving the growth of a lithium-rich compound on a current collector/catalyst support.
\r\n\r\nWe begin by describing the effect of using a molten salt electrolyte in a lithium-oxygen battery. In particular, we focus on how the electrochemical performance and discharge product, lithium peroxide, differ from that of a traditional organic electrolyte. In addition, we discuss the enhanced peroxide solubility in a molten salt and its implications for lithium peroxide growth and coulombic efficiency. Finally, we address the cell death of a galvanostatically cycled battery.
\r\n\r\nWe then introduce a similar phase-forming conversion chemistry, whereby a molten nitrate salt serves as both an active material and the electrolyte. Molten nitrate salts were previously studied as an active material in a primary lithium battery where lithium oxide irreversibly forms as nitrate reduces to nitrite. We will describe how the use of a nanoparticle heterogeneous catalyst allows the reversible growth and dissolution of micron-scale lithium oxide crystals in this system.
\r\n\r\nAfter introducing these molten salt lithium batteries, we address the effect of cathode geometry on electrochemical performance. In particular, we note that the growth of such large, solid phase species on the surface of the catalyst support imposes new design restrictions when optimizing a cathode for energy density. As a proof of concept, we design and implement an architected electrode with large pore volume and relatively small surface area, comparing it with the more typical geometries of thin films and nanoparticles.
", "doi": "10.7907/TG0K-8776", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:11037", "collection": "thesis", "collection_id": "11037", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06072018-140534228", "type": "thesis", "title": "Cathode Design for High Energy Molten Salt Lithium-Oxygen Batteries", "author": [ { "family_name": "Tozier", "given_name": "Dylan Douglas", "orcid": "0000-0001-9489-8824", "clpid": "Tozier-Dylan-Douglas" } ], "thesis_advisor": [ { "family_name": "Greer", "given_name": "Julia R.", "orcid": "0000-0002-9675-1508", "clpid": "Greer-J-R" } ], "thesis_committee": [ { "family_name": "Fultz", "given_name": "Brent T.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B-T" }, { "family_name": "Greer", "given_name": "Julia R.", "orcid": "0000-0002-9675-1508", "clpid": "Greer-J-R" }, { "family_name": "Johnson", "given_name": "William Lewis", "clpid": "Johnson-W-L" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "State of the art commercial lithium ion batteries use cathodes such as lithium cobalt oxide which rely on insertion and removal of lithium ions from a host material. However, insertion cathode materials are limited in their capacity, and replacing them with a cathode that employs growth and dissolution of new phases could significantly increase a battery\u2019s energy density. For example, oxygen and sulfur cathodes have been widely researched to this end, with both cases involving the growth of a lithium-rich compound on a current collector/catalyst support.
\r\n\r\nWe begin by describing the effect of using a molten salt electrolyte in a lithium-oxygen battery. In particular, we focus on how the electrochemical performance and discharge product, lithium peroxide, differ from that of a traditional organic electrolyte. In addition, we discuss the enhanced peroxide solubility in a molten salt and its implications for lithium peroxide growth and coulombic efficiency. Finally, we address the cell death of a galvanostatically cycled battery.
\r\n\r\nWe then introduce a similar phase-forming conversion chemistry, whereby a molten nitrate salt serves as both an active material and the electrolyte. Molten nitrate salts were previously studied as an active material in a primary lithium battery where lithium oxide irreversibly forms as nitrate reduces to nitrite. We will describe how the use of a nanoparticle heterogeneous catalyst allows the reversible growth and dissolution of micron-scale lithium oxide crystals in this system.
\r\n\r\nAfter introducing these molten salt lithium batteries, we address the effect of cathode geometry on electrochemical performance. In particular, we note that the growth of such large, solid phase species on the surface of the catalyst support imposes new design restrictions when optimizing a cathode for energy density. As a proof of concept, we design and implement an architected electrode with large pore volume and relatively small surface area, comparing it with the more typical geometries of thin films and nanoparticles.
", "doi": "10.7907/TG0K-8776", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" } ]