skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Understanding and Design of Bidirectional and Reversible Catalysts of Multielectron, Multistep Reactions

Abstract

The catalytic properties of the enzymes that transform H2 set very high standards for chemists who aim at designing synthetic electrocatalysts of H2 oxidation and production. Of particular relevance is the observation that some hydrogenases wired to electrodes function in either direction of the reaction depending on the driving force that is applied, and at a significant rate as a result of even a very small deviation from equilibrium. We call the former property "bidirectionality", and the latter "reversibility". Bidirectional and reversible catalysts of H2 oxidation and production have only recently been synthesized. Here we introduce the kinetic modelling of bidirectional two-electron redox reactions in the case of molecular catalysts and enzymes that are either attached to an electrode or diffusing in solution in the vicinity of an electrode. Our theoretical findings are illustrated by previous results obtained with hydrogenases and Nickel diphosphine molecular catalysts. We emphasize that trying to discuss bidirectionality and reversibility in relation to a single redox potential leads to an impasse: the catalyst undergoes two redox transitions, and two catalytic potentials must be defined, which may depart from the two potentials measured in the absence of catalysis. The difference between the two catalytic potentials defines themore » reversibility; the difference between their average value and the open circuit potential defines the directionality. We aim at giving rules that help discriminate between distinct mechanisms ("ECEC", "EECC" etc.) based on the voltammetric responses, and we discuss the design principles of bidirectionality and reversibility in terms of kinetics. In particular we conclude that neither bidirectionality nor reversibility requires that the catalytic energy landscape be flat. However, sinks and high energy intermediates may negatively impact the catalytic rates. The "efficiency" of a bidirectional catalyst appears to be defined by various figures of merit (rates, directionality, reversibility) that need to be recognized before they can be optimized simultaneously. E.S.W. was supported by the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy (USDOE), Office of Science, Office of Basic Energy Sciences (BES). The work discussed here was originally supported for WJS by the Office of Science Early Career Research Program through the USDOE, with current funding from the USDOE, BES, Chemical Sciences, Geosciences, and Biosciences program.« less

Authors:
 [1]; ORCiD logo [2]; ORCiD logo [2];  [1]
  1. Aix-Marseille Université
  2. BATTELLE (PACIFIC NW LAB)
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1571487
Report Number(s):
PNNL-SA-140275
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 141; Journal Issue: 28
Country of Publication:
United States
Language:
English

Citation Formats

Fourmond, Vincent, Wiedner, Eric S., Shaw, Wendy J., and Leger, Christophe. Understanding and Design of Bidirectional and Reversible Catalysts of Multielectron, Multistep Reactions. United States: N. p., 2019. Web. doi:10.1021/jacs.9b04854.
Fourmond, Vincent, Wiedner, Eric S., Shaw, Wendy J., & Leger, Christophe. Understanding and Design of Bidirectional and Reversible Catalysts of Multielectron, Multistep Reactions. United States. doi:10.1021/jacs.9b04854.
Fourmond, Vincent, Wiedner, Eric S., Shaw, Wendy J., and Leger, Christophe. Wed . "Understanding and Design of Bidirectional and Reversible Catalysts of Multielectron, Multistep Reactions". United States. doi:10.1021/jacs.9b04854.
@article{osti_1571487,
title = {Understanding and Design of Bidirectional and Reversible Catalysts of Multielectron, Multistep Reactions},
author = {Fourmond, Vincent and Wiedner, Eric S. and Shaw, Wendy J. and Leger, Christophe},
abstractNote = {The catalytic properties of the enzymes that transform H2 set very high standards for chemists who aim at designing synthetic electrocatalysts of H2 oxidation and production. Of particular relevance is the observation that some hydrogenases wired to electrodes function in either direction of the reaction depending on the driving force that is applied, and at a significant rate as a result of even a very small deviation from equilibrium. We call the former property "bidirectionality", and the latter "reversibility". Bidirectional and reversible catalysts of H2 oxidation and production have only recently been synthesized. Here we introduce the kinetic modelling of bidirectional two-electron redox reactions in the case of molecular catalysts and enzymes that are either attached to an electrode or diffusing in solution in the vicinity of an electrode. Our theoretical findings are illustrated by previous results obtained with hydrogenases and Nickel diphosphine molecular catalysts. We emphasize that trying to discuss bidirectionality and reversibility in relation to a single redox potential leads to an impasse: the catalyst undergoes two redox transitions, and two catalytic potentials must be defined, which may depart from the two potentials measured in the absence of catalysis. The difference between the two catalytic potentials defines the reversibility; the difference between their average value and the open circuit potential defines the directionality. We aim at giving rules that help discriminate between distinct mechanisms ("ECEC", "EECC" etc.) based on the voltammetric responses, and we discuss the design principles of bidirectionality and reversibility in terms of kinetics. In particular we conclude that neither bidirectionality nor reversibility requires that the catalytic energy landscape be flat. However, sinks and high energy intermediates may negatively impact the catalytic rates. The "efficiency" of a bidirectional catalyst appears to be defined by various figures of merit (rates, directionality, reversibility) that need to be recognized before they can be optimized simultaneously. E.S.W. was supported by the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy (USDOE), Office of Science, Office of Basic Energy Sciences (BES). The work discussed here was originally supported for WJS by the Office of Science Early Career Research Program through the USDOE, with current funding from the USDOE, BES, Chemical Sciences, Geosciences, and Biosciences program.},
doi = {10.1021/jacs.9b04854},
journal = {Journal of the American Chemical Society},
number = 28,
volume = 141,
place = {United States},
year = {2019},
month = {7}
}