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An NADH-Inspired Redox Mediator Strategy to Promote Second-Sphere Electron and Proton Transfer for Cooperative Electrochemical CO2 Reduction Catalyzed by Iron Porphyrin

preprint
submitted on 20.04.2020, 20:12 and posted on 22.04.2020, 12:07 by Peter T. Smith, Sophia Weng, Christopher Chang
We present a bioinspired strategy for enhancing electrochemical carbon dioxide reduction catalysis by cooperative use of base-metal molecular catalysts with intermolecular second-sphere redox mediators that facilitate both electron and proton transfer. Functional synthetic mimics of the biological redox cofactor NADH, which are electrochemically stable and are capable of mediating both electron and proton transfer, can enhance the activity of an iron porphyrin catalyst for electrochemical reduction of CO2 to CO, achieving a 13-fold rate improvement without altering the intrinsic high selectivity of this catalyst platform for CO2 versus proton reduction. Evaluation of a systematic series of NADH analogs and redox-inactive control additives with varying proton and electron reservoir properties reveals that both electron and proton transfer contribute to the observed catalytic enhancements. This work establishes that second-sphere dual control of electron and proton inventories is a viable design strategy for developing more effective electrocatalysts for CO2 reduction, providing a starting point for broader applications of this approach to other multi-electron, multi-proton transformations.

Funding

Lawrence Berkeley National Laboratory (DE-AC02-05CH11231)

National Science Foundation GRFP (DGE 1752814)

History

Email Address of Submitting Author

peter.smith@berkeley.edu

Institution

University of California, Berkeley

Country

United States

ORCID For Submitting Author

0000-0002-8892-3752

Declaration of Conflict of Interest

The authors declare no conflict of interest.

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