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Title: Graphite Conjugation Eliminates Redox Intermediates in Molecular Electrocatalysis

Abstract

The efficient interconversion of electrical and chemical energy requires the intimate coupling of electrons and small-molecule substrates at catalyst active sites. In molecular electrocatalysis, the molecule acts as a redox mediator which typically undergoes oxidation or reduction in a separate step from substrate activation. These mediated pathways introduce a high-energy intermediate, cap the driving force for substrate activation at the reduction potential of the molecule, and impede access to high rates at low overpotentials. Here we show that electronically coupling a molecular hydrogen evolution catalyst to a graphitic electrode eliminates stepwise pathways and forces concerted electron transfer and proton binding. Electrochemical and X-ray absorption spectroscopy data establish that hydrogen evolution catalysis at the graphite-conjugated Rh molecule proceeds without first reducing the metal center. These results have broad implications for the molecular-level design of energy conversion catalysts.

Authors:
 [1];  [2];  [2];  [2]; ORCiD logo [2]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Univ. of California, Berkeley, CA (United States)
  2. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Publication Date:
Research Org.:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1561558
Grant/Contract Number:  
SC0014176
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 141; Journal Issue: 36; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Jackson, Megan N., Kaminsky, Corey J., Oh, Seokjoon, Melville, Jonathan F., and Surendranath, Yogesh. Graphite Conjugation Eliminates Redox Intermediates in Molecular Electrocatalysis. United States: N. p., 2019. Web. doi:10.1021/jacs.9b04981.
Jackson, Megan N., Kaminsky, Corey J., Oh, Seokjoon, Melville, Jonathan F., & Surendranath, Yogesh. Graphite Conjugation Eliminates Redox Intermediates in Molecular Electrocatalysis. United States. doi:10.1021/jacs.9b04981.
Jackson, Megan N., Kaminsky, Corey J., Oh, Seokjoon, Melville, Jonathan F., and Surendranath, Yogesh. Mon . "Graphite Conjugation Eliminates Redox Intermediates in Molecular Electrocatalysis". United States. doi:10.1021/jacs.9b04981. https://www.osti.gov/servlets/purl/1561558.
@article{osti_1561558,
title = {Graphite Conjugation Eliminates Redox Intermediates in Molecular Electrocatalysis},
author = {Jackson, Megan N. and Kaminsky, Corey J. and Oh, Seokjoon and Melville, Jonathan F. and Surendranath, Yogesh},
abstractNote = {The efficient interconversion of electrical and chemical energy requires the intimate coupling of electrons and small-molecule substrates at catalyst active sites. In molecular electrocatalysis, the molecule acts as a redox mediator which typically undergoes oxidation or reduction in a separate step from substrate activation. These mediated pathways introduce a high-energy intermediate, cap the driving force for substrate activation at the reduction potential of the molecule, and impede access to high rates at low overpotentials. Here we show that electronically coupling a molecular hydrogen evolution catalyst to a graphitic electrode eliminates stepwise pathways and forces concerted electron transfer and proton binding. Electrochemical and X-ray absorption spectroscopy data establish that hydrogen evolution catalysis at the graphite-conjugated Rh molecule proceeds without first reducing the metal center. These results have broad implications for the molecular-level design of energy conversion catalysts.},
doi = {10.1021/jacs.9b04981},
journal = {Journal of the American Chemical Society},
issn = {0002-7863},
number = 36,
volume = 141,
place = {United States},
year = {2019},
month = {7}
}

Journal Article:
Free Publicly Available Full Text
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Cited by: 1 work
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Figures / Tables:

Figure 1 Figure 1: Mechanistic pathways and corresponding free energy diagrams for hydrogen evolution catalysis at a molecule vs graphite-conjugated catalyst. (a) Molecular catalyst (M) mediates the conversion of 2 H+ and 2 e to H2 through a stepwise pathway involving two-electron transfer followed by substrate activation. (b) Free energy diagram formore » the catalytic cycle in part a. (c) Graphite-conjugated M catalyzes the conversion of 2 H+ and 2 e to H2 directly through an M−H intermediate on the surface. (d) Free energy diagram for the catalytic cycle in part c. $F$ is Faraday’s constant, $E$applied is the applied potential, and $ΔG$$s$ is the driving force for forming the M−H intermediate.« less

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