[ { "id": "authors:tjjm8-1kj30", "collection": "authors", "collection_id": "tjjm8-1kj30", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230324-7219000.2", "type": "monograph", "title": "Beyond Tafel Analysis for Electrochemical CO\u2082 Reduction", "author": [ { "family_name": "Corpus", "given_name": "Kaitlin Rae M.", "clpid": "Corpus-Kaitlin-Rae-M" }, { "family_name": "Bui", "given_name": "Justin C.", "orcid": "0000-0003-4525-957X", "clpid": "Bui-Justin-C" }, { "family_name": "Limaye", "given_name": "Aditya M.", "orcid": "0000-0003-0639-4154", "clpid": "Limaye-Aditya-M" }, { "family_name": "Pant", "given_name": "Lalit M.", "orcid": "0000-0002-0432-3902", "clpid": "Pant-Lalit-M" }, { "family_name": "Manthiram", "given_name": "Karthish", "orcid": "0000-0001-9260-3391", "clpid": "Manthiram-Karthish" }, { "family_name": "Weber", "given_name": "Adam Z.", "orcid": "0000-0002-7749-1624", "clpid": "Weber-Adam-Z" }, { "family_name": "Bell", "given_name": "Alexis T.", "orcid": "0000-0002-5738-4645", "clpid": "Bell-Alexis-T" } ], "abstract": "The development and characterization of active and selective catalysts is critical for the simulation and optimization of electrochemical synthesis of chemicals and fuels using renewable energy. The rate of electrochemical generation of a specific product as a function of electrode potential can be described by a Tafel equation, which depends on two parameters: the Tafel slope (or the related transfer coefficient) and the exchange current density. However, common methods for calculating Tafel slopes are subjective and limited by data insufficiency resulting from challenges associated with product quantification, and, as shown here, the effects of mass transport, bulk reaction occurring in the mass-transfer boundary layer, and the occurrence of competitive surface reactions. Errors in the Tafel slope extracted from experimental data can also lead to errors in the exchange current density estimation. To address these issues, we present a technique that leverages statistical learning methods informed by physics-based modeling to calculate kinetic parameters (the transfer coefficient and exchange current density) with quantified uncertainty. The method is applied to 21 sets of data for the electrochemical reduction of CO\u2082 to CO and H\u2082 on Ag catalysts acquired under similar experimental conditions. We find that fitted values for the transfer coefficient and exchange current density do not converge to a unique set of values, and that there is an apparent correlation of these parameters; however, the most probable value of the exchange coefficient for CO and H\u2082 formation correspond reasonably well with the DFT-predicted values of this parameter. While the system explored is relatively simple, the techniques developed can be used to evaluate the transfer coefficient and exchange current density for many other electrochemical processes.", "doi": "10.26434/chemrxiv-2022-9rx0m", "publication_date": "2022-11-28" }, { "id": "authors:6m1a8-hv988", "collection": "authors", "collection_id": "6m1a8-hv988", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220414-26022000", "type": "monograph", "title": "Imaging nitrogen fixation at lithium solid electrolyte interphases via cryo-electron microscopy", "author": [ { "family_name": "Steinberg", "given_name": "Katherine", "orcid": "0000-0002-8232-7714", "clpid": "Steinberg-Katherine" }, { "family_name": "Yuan", "given_name": "Xintong", "clpid": "Yuan-Xintong" }, { "family_name": "Lazouski", "given_name": "Nikifar", "orcid": "0000-0002-4655-2041", "clpid": "Lazouski-Nikifar" }, { "family_name": "Klein", "given_name": "Channing K.", "clpid": "Klein-Channing-K" }, { "family_name": "Manthiram", "given_name": "Karthish", "orcid": "0000-0001-9260-3391", "clpid": "Manthiram-Karthish" }, { "family_name": "Li", "given_name": "Yuzhang", "clpid": "Li-Yuzhang" } ], "abstract": "Electrifying ammonia synthesis will be vital to the decarbonization of the chemical industry, as the Haber-Bosch process contributes significantly to global carbon emissions. A lithium-mediated pathway is among the most promising ambient-condition electrochemical ammonia synthesis methods. However, the role of metallic lithium and its passivation layer, the solid electrolyte interphase (SEI), remains unresolved. Here, we apply a multiscale approach that leverages the powerful cryogenic transmission electron microscopy (cryo-TEM) technique to reveal new insights that were previously inaccessible with conventional methods. We discover that the proton donor (e.g. ethanol) governs lithium reactivity toward nitrogen fixation. Without ethanol, the SEI passivates lithium metal, rendering it inactive for ammonia production. Ethanol disrupts this passivation layer, enabling continuous reactivity at the lithium surface. As a result, metallic lithium is consumed via reactions with nitrogen, proton donor, and other electrolyte components. This reactivity across the SEI is vital to device-level performance of lithium-mediated ammonia synthesis.", "doi": "10.26434/chemrxiv-2022-9v3nw", "publication_date": "2022-04-08" }, { "id": "authors:dxz9t-6xj27", "collection": "authors", "collection_id": "dxz9t-6xj27", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220505-564477000", "type": "monograph", "title": "Selective Electrochemical Reductive Amination of Benzaldehyde at Heterogeneous Metal Surfaces", "author": [ { "family_name": "Schiffer", "given_name": "Zachary J.", "orcid": "0000-0001-6069-8613", "clpid": "Schiffer-Zachary-J" }, { "family_name": "Chung", "given_name": "Minju", "orcid": "0000-0003-4359-7508", "clpid": "Chung-Minju" }, { "family_name": "Steinberg", "given_name": "Katherine", "orcid": "0000-0002-8232-7714", "clpid": "Steinberg-Katherine-J" }, { "family_name": "Manthiram", "given_name": "Karthish", "orcid": "0000-0001-9260-3391", "clpid": "Manthiram-Karthish" } ], "abstract": "Ammonia is one of the largest volume commodity chemicals, and electrochemical routes to ammonia utilization are appealing due to increasingly available renewable electricity. In this work, we demonstrate an electrochemical analogue to reductive amination for the synthesis of benzylamine from benzaldehyde and ammonia. Previous works on electrochemical reductive amination generally focus on proof-of-concept outer-sphere routes. We demonstrate an inner-sphere route, opening a large phase space of heterogeneous electrocatalysts that can direct selectivity and drive the reaction. In our system, imine hydrogenation proceeds on a silver electrocatalyst at ambient conditions in methanol with an initial Faradaic efficiency toward the primary amine product of ~80% and partial current greater than 4 mA/cm\u00b2 at -1.96 V vs. Fc/Fc\u207a (-1.36 V vs. NHE). Silver was selected after evaluating diverse transition metal electrocatalysts, and with density functional theory, we found that the reaction rate on various metals is best described by the charge density distribution above the metal surface, independent of molecular adsorption energies. On silver, the catalyst that promotes amination with the highest Faradaic efficiency and one of the highest partial currents, the rate-determining step was found to be the initial electron transfer to the imine. Overall, this work on the kinetics of electrochemical reductive amination represents a step toward inner-sphere electrochemical reductive amination systems for the synthesis of amines that currently rely on thermochemical reductive amination.", "doi": "10.26434/chemrxiv-2022-2s2z7", "publication_date": "2022-02-18" }, { "id": "authors:ge8sz-tzz21", "collection": "authors", "collection_id": "ge8sz-tzz21", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220505-565017000", "type": "monograph", "title": "Accounting for species' thermodynamic activities changes mechanistic interpretations of electrochemical kinetic data", "author": [ { "family_name": "Williams", "given_name": "Kindle", "orcid": "0000-0001-9640-7849", "clpid": "Williams-Kindle" }, { "family_name": "Limaye", "given_name": "Aditya", "orcid": "0000-0003-0639-4154", "clpid": "Limaye-Aditya" }, { "family_name": "Weiss", "given_name": "Trent", "clpid": "Weiss-Trent" }, { "family_name": "Chung", "given_name": "Minju", "orcid": "0000-0003-4359-7508", "clpid": "Ching-Minju" }, { "family_name": "Manthiram", "given_name": "Karthish", "orcid": "0000-0001-9260-3391", "clpid": "Manthiram-Karthish" } ], "abstract": "The thermodynamic activity of a reacting species, rather than the concentration of that species, generally determines the rate of a kinetically-limited reaction. In this work we demonstrate the need for the explicit accounting of reacting species' thermodynamic activities in solution, especially when conducting electrochemical kinetic tests. In hydrogen evolution in an alkaline acetonitrile-water blended electrolyte as well as previously-reported oxygen-atom transfer reactions (cyclooctene epoxidation and cyclohexanone lactonization), we demonstrate that accounting for species thermodynamic activity causes water-dependence measurements to yield different mechanistic interpretations than data which treats concentration as a proxy for activity. We hypothesize many ways in which water contributes to the reaction rate beyond direct participation in the reaction, offer initial molecular interpretations of the water activity-concentration relationship in the blended electrolyte, and discuss implications of these findings for better understanding solvent effects.", "doi": "10.26434/chemrxiv-2022-vk5z9", "publication_date": "2022-02-17" } ]