[ { "id": "https://authors.library.caltech.edu/records/x6vtx-82q67", "eprint_id": 120380, "eprint_status": "archive", "datestamp": "2023-08-20 16:41:16", "lastmod": "2023-10-18 16:07:49", "type": "monograph", "metadata_visibility": "show", "creators": { "items": [ { "id": "Watkins-Nicholas-B", "name": { "family": "Watkins", "given": "Nicholas B." }, "orcid": "0000-0001-7251-9387" }, { "id": "Schiffer-Zachary-J", "name": { "family": "Schiffer", "given": "Zachary J." }, "orcid": "0000-0001-6069-8613" }, { "id": "Lai-Yungchieh", "name": { "family": "Lai", "given": "Yungchieh" }, "orcid": "0000-0001-9392-1447" }, { "id": "Musgrave-Charles-B-III", "name": { "family": "Musgrave", "given": "Charles B., III" }, "orcid": "0000-0002-3432-0817" }, { "id": "Atwater-H-A", "name": { "family": "Atwater", "given": "Harry A." }, "orcid": "0000-0001-9435-0201" }, { "id": "Goddard-W-A-III", "name": { "family": "Goddard", "given": "William A., III" }, "orcid": "0000-0003-0097-5716" }, { "id": "Agapie-T", "name": { "family": "Agapie", "given": "Theodor" }, "orcid": "0000-0002-9692-7614" }, { "id": "Peters-J-C", "name": { "family": "Peters", "given": "Jonas" }, "orcid": "0000-0002-6610-4414" }, { "id": "Gregoire-J-M", "name": { "family": "Gregoire", "given": "John M." }, "orcid": "0000-0002-2863-5265" } ] }, "title": "Hydrodynamics Determine Tafel Slopes in Electrochemical CO\u2082 Reduction on Copper", "ispublished": "unpub", "full_text_status": "public", "note": "The content is available under CC BY NC 4.0 License. \n\nThis material is based on work\tperformed by the Liquid Sun-light Alliance, which is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Fuels from Sunlight Hub under Award Number DE-SC0021266. The Resnick Sustainability Institute at Caltech is acknowledged for its\tsupport of enabling infrastructure and facilities. We thank Dr. Ian Sullivan for many productive conversations and Annette Boehme for initial insights into COMSOL calculations of the cells investigated. \n\nThe authors declare no competing financial interests.\n\n
Submitted - hydrodynamics-determine-tafel-slopes-in-electrochemical-co2-reduction-on-copper.pdf
Supplemental Material - supplementary-materials.pdf
", "abstract": "The hydrodynamics of electrochemical CO\u2082 reduction (CO\u2082) systems is an insufficiently investigated area of research that has broad implications on catalyst activity and selectivity. While most previous reports are limited to laminar and CO\u2082-sparged systems, herein we address a wide range of hydrodynamics via electrolyte recirculation systems. We find that increased hydrodynamics at the electrode surface results directly in changes to the ethylene and methane Tafel slopes, demonstrating that mass transport is on equal footing with catalyst active sites in determining reaction mechanisms and the ensuing product distribution. Mass transport is traditionally considered to be in the purview of systems-level engineering, yet the present work shows that CO\u2082R mechanistic work must be considered in the context of the mass transport conditions. We extend our analysis to organic coatings, demonstrating that the films shield the active sites from variability in hydrodynamics and increase the residence time of CO so that it may be further reduced to desirable products.", "date": "2023-03-29", "date_type": "published", "id_number": "CaltechAUTHORS:20230324-864199000.4", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230324-864199000.4", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE)", "grant_number": "DE-SC0021266" }, { "agency": "Resnick Sustainability Institute" } ] }, "local_group": { "items": [ { "id": "Resnick-Sustainability-Institute" }, { "id": "Liquid-Sunlight-Alliance" } ] }, "doi": "10.26434/chemrxiv-2023-npdmn", "primary_object": { "basename": "hydrodynamics-determine-tafel-slopes-in-electrochemical-co2-reduction-on-copper.pdf", "url": "https://authors.library.caltech.edu/records/x6vtx-82q67/files/hydrodynamics-determine-tafel-slopes-in-electrochemical-co2-reduction-on-copper.pdf" }, "related_objects": [ { "basename": "supplementary-materials.pdf", "url": "https://authors.library.caltech.edu/records/x6vtx-82q67/files/supplementary-materials.pdf" } ], "resource_type": "monograph", "pub_year": "2023", "author_list": "Watkins, Nicholas B.; Schiffer, Zachary J.; et el." }, { "id": "https://authors.library.caltech.edu/records/htx5s-vyf77", "eprint_id": 115144, "eprint_status": "archive", "datestamp": "2023-08-20 07:57:11", "lastmod": "2023-10-24 15:25:21", "type": "monograph", "metadata_visibility": "show", "creators": { "items": [ { "id": "Johansen-Christian-M", "name": { "family": "Johansen", "given": "Christian M." } }, { "id": "Boyd-Emily-A", "name": { "family": "Boyd", "given": "Emily A." }, "orcid": "0000-0003-0150-5396" }, { "id": "Peters-J-C", "name": { "family": "Peters", "given": "Jonas C." }, "orcid": "0000-0002-6610-4414" } ] }, "title": "Photoinduced transfer hydrogenation of nitrogen to ammonia using a Mo-catalyst and a Hantzsch ester donor is demonstrated with and without an Ir-photoredox co-catalyst", "ispublished": "unpub", "full_text_status": "public", "note": "The content is available under CC BY NC ND 4.0 License. \n\nWe thank the Dow Next Generation Educator Fund and Instrumentation Grants for their support of the NMR facility at Caltech. The Beckman Institute Laser Resource Center and Jay R. Winkler are acknowledged for providing support with steady-state luminescence experiments. We also thank the Resnick Sustainability Institute Water and 5 Environment Laboratory (WEL) at Caltech for the use of their instrumentation. \n\nFunding: National Institutes of Health (R01 GM-075757) \nEAB acknowledges the support of the National Science Foundation for a Graduate Research Fellowship under Grant No. DGE\u20101745301 \n\nAuthors declare that they have no competing interests. \n\nData and materials availability: All data are available in the main text or the supporting information.\n\nSupplemental Material - supporting-information.pdf
", "abstract": "Whereas photoredox catalysis using molecular systems enjoys considerable utility in small molecule transformations and reactions relevant to organic synthesis, to date there are no related examples of photodriven catalytic nitrogen fixation. We wondered whether a photoinduced transfer hydrogenation strategy might provide a viable pathway toward such a reaction. Hantzsch esters (and related organic structures) offer an opportunity for catalysis design in this context as they can behave as photoreductants, though to our knowledge they had yet to be shown to be compatible with such a redox intensive process (6 e\u207b/6 H\u207a). In the present study we demonstrate that fully reduced Hantzsch esters (abbreviated as HEH2) successively deliver stored H\u2082-equivalents to N\u2082, producing NH\u2083 catalytically, in the presence of a molecular precatalyst (Mo) under blue-light irradiation but otherwise ambient conditions. While not required for the observed photocatalysis, the addition of a photoredox catalyst (Ir) to the reaction mixture enhances both the rate and turnover number of the net transformation. Encouraging with respect to future studies toward recycling the donor, electrochemically or via hydrogenation, other N-heterocycle H\u2082-donors are also compatible with catalysis in the presence of the photoredox catalyst. The reduction of N\u2082 to NH\u2083 by HEH\u2082 or H\u2082 are thermodynamically very similar (\u0394\u0394G_f(NH\u2083) = 1.8 kcal mol\u207b\u00b9 in acetonitrile). However, whereas the combination of H\u2082 with N\u2082 to produce NH\u2083 is accomplished via high temperature and pressure over a metal catalyst, the needed overpotential to drive the reduction of N\u2082 by HEH\u2082 can instead be derived from light. This study hence illustrates a promising photoredox catalysis approach toward deep reduction of robust small molecule substrates via photoinduced transfer hydrogenation, with the complete reduction of the triple bond of N\u2082 providing a vivid example.", "date": "2022-06-15", "date_type": "published", "id_number": "CaltechAUTHORS:20220614-222105000", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220614-222105000", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Dow Next Generation Educator Fund" }, { "agency": "Resnick Sustainability Institute" }, { "agency": "NSF Graduate Research Fellowship", "grant_number": "DGE-1745301" }, { "agency": "NIH", "grant_number": "R01 GM-075757" } ] }, "local_group": { "items": [ { "id": "Resnick-Sustainability-Institute" } ] }, "doi": "10.26434/chemrxiv-2022-sn16v", "primary_object": { "basename": "photoinduced-transfer-hydrogenation-of-nitrogen-to-ammonia-using-a-mo-catalyst-and-a-hantzsch-ester-donor-is-demonstrated-with-and-without-an-ir-photoredox-co-catalyst.pdf", "url": "https://authors.library.caltech.edu/records/htx5s-vyf77/files/photoinduced-transfer-hydrogenation-of-nitrogen-to-ammonia-using-a-mo-catalyst-and-a-hantzsch-ester-donor-is-demonstrated-with-and-without-an-ir-photoredox-co-catalyst.pdf" }, "related_objects": [ { "basename": "supporting-information.pdf", "url": "https://authors.library.caltech.edu/records/htx5s-vyf77/files/supporting-information.pdf" } ], "resource_type": "monograph", "pub_year": "2022", "author_list": "Johansen, Christian M.; Boyd, Emily A.; et el." }, { "id": "https://authors.library.caltech.edu/records/zmvd8-r2r05", "eprint_id": 111462, "eprint_status": "archive", "datestamp": "2023-08-22 11:36:03", "lastmod": "2023-10-23 20:35:28", "type": "monograph", "metadata_visibility": "show", "creators": { "items": [ { "id": "Garrido-Barros-Pablo", "name": { "family": "Garrido-Barros", "given": "Pablo" }, "orcid": "0000-0002-1489-3386" }, { "id": "Derosa-Joseph", "name": { "family": "Derosa", "given": "Joseph" }, "orcid": "0000-0001-8672-4875" }, { "id": "Chalkley-Matthew-J", "name": { "family": "Chalkley", "given": "Matthew J." }, "orcid": "0000-0002-0484-7335" }, { "id": "Peters-J-C", "name": { "family": "Peters", "given": "Jonas" }, "orcid": "0000-0002-6610-4414" } ] }, "title": "Tandem electrocatalytic N\u2082 fixation via concerted proton-electron transfer", "ispublished": "unpub", "full_text_status": "public", "keywords": "nitrogen fixation; N2RR; Electrocatalytic N2RR; CPET; tandem catalysis; Electrocatalysis", "note": "The content is available under CC BY NC ND 4.0 License. \n\nWe thank the Dow Next Generation Educator Funds and Instrumentation Grants for their support of the NMR facility at Caltech.\nWe also thank the Resnick Water and Environment Laboratory at Caltech for the use of their instrumentation. We thank the following funding agencies: Department of Energy, Office of Basic Energy Sciences (DOE-0235032), Catalysis Science Program (for the development and applications of CPET mediators); National Institutes of Health (R01 GM-075757) (for studies of Fe-mediated N\u2082RR). P.G.B. thanks the Ram\u00f3n Areces Foundation for a postdoctoral fellowship. J.D. thanks the Arnold and Mabel Beckman Foundation for a postdoctoral fellowship. M.J.C. thanks the Resnick Sustainability Institute for a graduate fellowship. \n\nAuthor Contributions: P.G.B., M.J.C. and J.C.P. conceptualized the work. P.G.B. designed and executed the experiments. J.D. assisted with the execution of the catalytic experiments. All authors analyzed, interpreted the data and cowrote the manuscript. \n\nThe authors declare no competing interests.\n\nSubmitted - tandem-electrocatalytic-n2-fixation-via-concerted-proton-electron-transfer.pdf
Supplemental Material - supplementary-information-for-tandem-electrocatalytic-n2-fixation-via-concerted-proton-electron-transfer.pdf
", "abstract": "New electrochemical ammonia (NH\u2083) synthesis technologies are of interest as a complementary route to the Haber-Bosch (HB) process for distributed fertilizer generation, and towards exploiting ammonia as a zero-carbon fuel produced via renewably-sourced electricity. Apropos of these goals is a surge of fundamental research targeting heterogeneous materials as electrocatalysts for the nitrogen reduction reaction (N\u2082RR). These systems generally suffer from poor stability and NH\u2083 selectivity; competitive hydrogen evolution reaction (HER) outcompetes N2RR. Molecular catalyst systems can be exquisitely tuned and offer an alternative strategy, but progress has thus far been thwarted by the same selectivity issue; HER dominates. Herein we describe a tandem catalysis strategy that offers a solution to this puzzle. A molecular complex that can mediate an N\u2082 reduction cycle is partnered with a co-catalyst that interfaces the electrode and an acid to mediate concerted proton-electron transfer (CPET) steps, facilitating N\u2212H bond formation at a favorable applied potential and overall thermodynamic efficiency. Without CPET, certain intermediates of the N\u2082RR cycle would be unreactive via independent electron transfer (ET) or proton transfer (PT) steps, thereby shunting the system. Promisingly, complexes featuring several metals (W, Mo, Os, Fe) achieve N\u2082RR electrocatalysis at the same applied potential in the presence of the CPET mediator, pointing to the generality of this tandem approach.", "date": "2021-10-18", "date_type": "published", "id_number": "CaltechAUTHORS:20211015-162627858", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20211015-162627858", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Department of Energy (DOE)", "grant_number": "DOE-0235032" }, { "agency": "NIH", "grant_number": "R01 GM-075757" }, { "agency": "Ram\u00f3n Areces Foundation" }, { "agency": "Arnold and Mabel Beckman Foundation" }, { "agency": "Resnick Sustainability Institute" } ] }, "local_group": { "items": [ { "id": "Resnick-Sustainability-Institute" } ] }, "doi": "10.33774/chemrxiv-2021-j95jg", "primary_object": { "basename": "supplementary-information-for-tandem-electrocatalytic-n2-fixation-via-concerted-proton-electron-transfer.pdf", "url": "https://authors.library.caltech.edu/records/zmvd8-r2r05/files/supplementary-information-for-tandem-electrocatalytic-n2-fixation-via-concerted-proton-electron-transfer.pdf" }, "related_objects": [ { "basename": "tandem-electrocatalytic-n2-fixation-via-concerted-proton-electron-transfer.pdf", "url": "https://authors.library.caltech.edu/records/zmvd8-r2r05/files/tandem-electrocatalytic-n2-fixation-via-concerted-proton-electron-transfer.pdf" } ], "resource_type": "monograph", "pub_year": "2021", "author_list": "Garrido-Barros, Pablo; Derosa, Joseph; et el." }, { "id": "https://authors.library.caltech.edu/records/qmta4-9m250", "eprint_id": 120400, "eprint_status": "archive", "datestamp": "2023-08-19 23:02:44", "lastmod": "2023-10-18 16:08:54", "type": "monograph", "metadata_visibility": "show", "creators": { "items": [ { "id": "Gu-Nina-X", "name": { "family": "Gu", "given": "Nina X." }, "orcid": "0000-0002-4637-8418" }, { "id": "Oyala-Paul-H", "name": { "family": "Oyala", "given": "Paul H." }, "orcid": "0000-0002-8761-4667" }, { "id": "Peters-J-C", "name": { "family": "Peters", "given": "Jonas C." }, "orcid": "0000-0002-6610-4414" } ] }, "title": "Hydrazine Formation via Ni\u1d35\u1d35\u1d35-NH\u2082 Radical Coupling in Ni-Mediated Ammonia Oxidation", "ispublished": "unpub", "full_text_status": "public", "note": "The content is available under CC BY NC ND 4.0 License. \n\nThe authors acknowledge Dr. Michael Takase and Lawrence Henling for assistance with X-ray crystallography. This work was supported by the National Institutes of Health (General Medical Sciences, grant GM070757) and an NSF-GRFP to N.X.G. The Caltech EPR facility is supported by the Dow Next Generation Educator Fund. The X-Ray Crystallography Facility in the Beckman Institute at Caltech has been supported by a Dow Next Generation Instrumentation Grant. \n\nThe authors declare no competing financial interests.\n\nSubmitted - hydrazine-formation-via-ni-iii-nh2-radical-coupling-in-ni-mediated-ammonia-oxidation.pdf
Supplemental Material - ni-nh2-si-chem-rxiv.pdf
", "abstract": "Given the diverse mechanistic possibilities for the overall 6e\u207b/6H\u207a transformation of ammonia to dinitrogen, identification of M(NH\u2093) intermediates involved in N\u2013N bond formation is a central mechanistic challenge. In analogy to water oxidation mechanisms, which widely invoke metal oxo intermediates, metal imide and nitride intermediates have commonly been proposed for ammonia oxidation, and stoichiometric demonstration of N\u2013N bond formation from these metal-ligand multiply bonded species is well-precedented. In contrast, while the homocoupling of M\u2013NH\u2082 species to form hydrazine has been hypothesized as the key N\u2013N bond forming step in certain molecular ammonia oxidation systems, well-defined examples of this transformation from M\u2013NH\u2082 complexes are essentially without precedent. This work reports the first example of net ammonia oxidation mediated by a molecular Ni species, a transformation carried out via formal Ni\u1d35\u1d35/Ni\u1d35\u1d35\u1d35 oxidation states. The available data are consistent with a N\u1d35\u1d35\u1d35\u2013NH\u2082 intermediate featuring substantial spin at N undergoing N\u2013N bond formation to generate a Ni\u1d35\u1d35\u2082(N\u2082H\u2084) complex. Additional and structurally unusual Ni_x(N_yH_z) species \u2013 including a Ni\u2082(trans-N\u2082H\u2082) complex \u2013 are characterized and studied as intermediates in the Ni-mediated ammonia oxidation cycle described herein.", "date": "2020-08-25", "date_type": "published", "id_number": "CaltechAUTHORS:20230324-457084000.3", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230324-457084000.3", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NIH", "grant_number": "GM070757" }, { "agency": "NSF Graduate Research Fellowship" }, { "agency": "Dow Next Generation Educator Fund" } ] }, "doi": "10.26434/chemrxiv.12858197.v1", "primary_object": { "basename": "hydrazine-formation-via-ni-iii-nh2-radical-coupling-in-ni-mediated-ammonia-oxidation.pdf", "url": "https://authors.library.caltech.edu/records/qmta4-9m250/files/hydrazine-formation-via-ni-iii-nh2-radical-coupling-in-ni-mediated-ammonia-oxidation.pdf" }, "related_objects": [ { "basename": "ni-nh2-si-chem-rxiv.pdf", "url": "https://authors.library.caltech.edu/records/qmta4-9m250/files/ni-nh2-si-chem-rxiv.pdf" } ], "resource_type": "monograph", "pub_year": "2020", "author_list": "Gu, Nina X.; Oyala, Paul H.; et el." } ]