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Tandem electrocatalytic N₂ fixation via concerted proton-electron transfer

Garrido-Barros, Pablo and Derosa, Joseph and Chalkley, Matthew J. and Peters, Jonas (2021) Tandem electrocatalytic N₂ fixation via concerted proton-electron transfer. . (Unpublished)

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New electrochemical ammonia (NH₃) 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 (N₂RR). These systems generally suffer from poor stability and NH₃ 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 N₂ 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−H bond formation at a favorable applied potential and overall thermodynamic efficiency. Without CPET, certain intermediates of the N₂RR 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 N₂RR electrocatalysis at the same applied potential in the presence of the CPET mediator, pointing to the generality of this tandem approach.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Garrido-Barros, Pablo0000-0002-1489-3386
Derosa, Joseph0000-0001-8672-4875
Chalkley, Matthew J.0000-0002-0484-7335
Peters, Jonas0000-0002-6610-4414
Alternate Title:Tandem electrocatalytic N2 fixation via concerted proton-electron transfer
Additional Information:The content is available under CC BY NC ND 4.0 License. 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 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. Author 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. The authors declare no competing interests.
Group:Resnick Sustainability Institute
Funding AgencyGrant Number
Department of Energy (DOE)DOE-0235032
NIHR01 GM-075757
Ramón Areces FoundationUNSPECIFIED
Arnold and Mabel Beckman FoundationUNSPECIFIED
Resnick Sustainability InstituteUNSPECIFIED
Subject Keywords:nitrogen fixation; N2RR; Electrocatalytic N2RR; CPET; tandem catalysis; Electrocatalysis
Record Number:CaltechAUTHORS:20211015-162627858
Persistent URL:
Official Citation:Garrido-Barros P, Derosa J, Chalkley M, Peters J. Tandem electrocatalytic N2 fixation via concerted proton-electron transfer. ChemRxiv. 2021. doi:10.33774/chemrxiv-2021-j95jg
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:111462
Deposited By: George Porter
Deposited On:18 Oct 2021 18:08
Last Modified:18 Oct 2021 18:08

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