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Tandem electrocatalytic N₂ fixation via proton-coupled electron transfer

Garrido-Barros, Pablo and Derosa, Joseph and Chalkley, Matthew J. and Peters, Jonas C. (2022) Tandem electrocatalytic N₂ fixation via proton-coupled electron transfer. Nature, 609 (7925). pp. 71-76. ISSN 0028-0836. doi:10.1038/s41586-022-05011-6.

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New electrochemical ammonia (NH₃) synthesis technologies are of interest as a complementary route to the Haber–Bosch 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 (N₂RR). These systems generally suffer from poor stability and NH₃ selectivity; the hydrogen evolution reaction (HER) outcompetes N₂RR. Molecular catalyst systems can be exquisitely tuned and offer an alternative strategy, but progress has been thwarted by the same selectivity issue; HER dominates. Here we describe a tandem catalysis strategy that offers a solution to this puzzle. A molecular complex that can mediate an N₂ reduction cycle is partnered with a co-catalyst that interfaces the electrode and an acid to mediate proton-coupled electron transfer steps, facilitating N−H bond formation at a favourable applied potential (−1.2 V versus Fc⁺/⁰) and overall thermodynamic efficiency. Certain intermediates of the N₂RR cycle would be otherwise unreactive via uncoupled electron transfer or proton transfer steps. Structurally diverse complexes of several metals (W, Mo, Os, Fe) also mediate N₂RR electrocatalysis at the same potential in the presence of the mediator, pointing to the generality of this tandem approach.

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URLURL TypeDescription ReadCube access InCaltech News ItemDiscussion Paper
Garrido-Barros, Pablo0000-0002-1489-3386
Derosa, Joseph0000-0001-8672-4875
Chalkley, Matthew J.0000-0002-0484-7335
Peters, Jonas C.0000-0002-6610-4414
Alternate Title:Tandem electrocatalytic N2 fixation via proton-coupled electron transfer, Tandem electrocatalytic N₂ fixation via concerted proton-electron transfer
Additional Information:We thank the Dow Next Generation Educator Funds and Instrumentation Grants for their support of the NMR facility at Caltech. We also thank the Resnick Water and Environment Laboratory (WEL) and the Molecular Materials Resource Center 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 N2RR). P.G.-B. thanks the Ramón 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.
Group:Resnick Sustainability Institute
Funding AgencyGrant Number
Department of Energy (DOE)DOE-0235032
NIHR01 GM-075757
Dow Next Generation Educator FundUNSPECIFIED
Ramón Areces FoundationUNSPECIFIED
Arnold and Mabel Beckman FoundationUNSPECIFIED
Resnick Sustainability InstituteUNSPECIFIED
Issue or Number:7925
Record Number:CaltechAUTHORS:20220916-665677000
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:117014
Deposited By: Olivia Warschaw
Deposited On:28 Oct 2022 22:32
Last Modified:28 Feb 2023 23:12

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