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Designing electrochemically reversible H2 oxidation and production catalysts


The most energy-efficient electrocatalysts mediate forward and reverse reactions at high rates with minimal overpotential requirements. Such electrocatalytic reversibility is commonly observed for redox enzymes and is an attribute that we have sought to bestow on synthetic molecules to realize highly active and robust catalysts for applications in renewable energy. The recent development of the first synthetic molecular catalysts that reversibly mediate H2 2 H+ + 2e exploits an enzyme-inspired outer coordination sphere that works in concert with both first and second coordination spheres. In this Perspective, we discuss a series of molecular Ni catalysts for H2 production and oxidation that exhibit electrochemical reversibility. Study of these catalysts allows us to identify important first, second and outer coordination sphere features necessary for efficient conversions of H2 and provides direction for the rational design of electrocatalysts that operate on other small molecules.

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Fig. 1: X-ray crystal structure of the [FeFe]-hydrogenase active site and surrounding residues.
Fig. 2: Simulated voltammograms for molecular catalysts.
Fig. 3: The square planar complexes [NiII(PR2NRʹ2)2]2+ heterolyse H2 to afford [Ni0(PR2NRʹ2H)2]2+.
Fig. 4: Amino acid-containing [NiII(PCy2NAminoacid2)2]2+ complexes feature a catalytically relevant H+ transfer chain.
Fig. 5: Reversible H2 oxidation mediated by bis(diphosphine)nickel complexes with pendant amino acids.
Fig. 6: The catalytic cycle for H2 oxidation and evolution mediated by [NiII(PCy2NAminoacid2)2]2+ complexes.
Fig. 7: [NiII(PCy2NAminoacid2)2]2+ complexes with interacting side chains exhibit high activity for H2 oxidation.
Fig. 8: CyAminoacid can be incorporated into a H2/air fuel cell.


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The authors thank E. S. Wiedner and D. L. DuBois for helpful discussions in the preparation of this document and E. Wiedner for assistance in providing electrochemical models. This Perspective reviews previously published work supported by the Office of Science Early Career Research Program through the US Department of Energy (DoE), Basic Energy Sciences (BES); US DoE BES, Chemical Sciences, Geoscience and Biosciences; US DoE BES, Physical Biosciences; and the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US DoE, Office of Science, Office of BES. Pacific Northwest National Laboratory (PNNL) is operated by Battelle for the US DoE. A.D. also acknowledges Indian Institute of Technology (IIT) Gandhinagar for their support.

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Dutta, A., Appel, A.M. & Shaw, W.J. Designing electrochemically reversible H2 oxidation and production catalysts. Nat Rev Chem 2, 244–252 (2018).

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