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Title: Molecular-Level Insights into Oxygen Reduction Catalysis by Graphite-Conjugated Active Sites

Abstract

With a combination of experimental and computational investigations, we design a consistent mechanistic model for the oxygen reduction reaction (ORR) at molecularly well-defined graphite-conjugated catalyst (GCC) active sites featuring aryl-pyridinium moieties (N+-GCC). ORR catalysis at glassy carbon surfaces modified with N+-GCC fragments displays near-first-order dependence in O2 partial pressure and near-zero-order dependence on electrolyte pH. Tafel analysis suggests an equilibrium one-electron transfer process followed by a rate-limiting chemical step at modest overpotentials that transitions to a rate-limiting electron transfer sequence at higher overpotentials. Finite-cluster computational modeling of the N+-GCC active site reveals preferential O2 adsorption at electrophilic carbons alpha to the pyridinium moiety. Together, the experimental and computational data indicate that ORR proceeds via a proton-decoupled O2 activation sequence involving either concerted or stepwise electron transfer and adsorption of O2, which is then followed by a series of electron/proton transfer steps to generate water and turn over the catalytic cycle. The introduced mechanistic model serves as a roadmap for the bottom-up synthesis of highly active N-doped carbon ORR catalysts.

Authors:
 [1]; ORCiD logo [1];  [1];  [1];  [1];  [1]; ORCiD logo [1]
  1. 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)
OSTI Identifier:
1557810
Grant/Contract Number:  
SC0014176
Resource Type:
Accepted Manuscript
Journal Name:
ACS Catalysis
Additional Journal Information:
Journal Volume: 7; Journal Issue: 11; Journal ID: ISSN 2155-5435
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; N-doped carbon; oxygen reduction; electrocatalysis; mechanistic studies; density functional theory

Citation Formats

Ricke, Nathan D., Murray, Alexander T., Shepherd, James J., Welborn, Matthew G., Fukushima, Tomohiro, Van Voorhis, Troy, and Surendranath, Yogesh. Molecular-Level Insights into Oxygen Reduction Catalysis by Graphite-Conjugated Active Sites. United States: N. p., 2017. Web. https://doi.org/10.1021/acscatal.7b03086.
Ricke, Nathan D., Murray, Alexander T., Shepherd, James J., Welborn, Matthew G., Fukushima, Tomohiro, Van Voorhis, Troy, & Surendranath, Yogesh. Molecular-Level Insights into Oxygen Reduction Catalysis by Graphite-Conjugated Active Sites. United States. https://doi.org/10.1021/acscatal.7b03086
Ricke, Nathan D., Murray, Alexander T., Shepherd, James J., Welborn, Matthew G., Fukushima, Tomohiro, Van Voorhis, Troy, and Surendranath, Yogesh. Mon . "Molecular-Level Insights into Oxygen Reduction Catalysis by Graphite-Conjugated Active Sites". United States. https://doi.org/10.1021/acscatal.7b03086. https://www.osti.gov/servlets/purl/1557810.
@article{osti_1557810,
title = {Molecular-Level Insights into Oxygen Reduction Catalysis by Graphite-Conjugated Active Sites},
author = {Ricke, Nathan D. and Murray, Alexander T. and Shepherd, James J. and Welborn, Matthew G. and Fukushima, Tomohiro and Van Voorhis, Troy and Surendranath, Yogesh},
abstractNote = {With a combination of experimental and computational investigations, we design a consistent mechanistic model for the oxygen reduction reaction (ORR) at molecularly well-defined graphite-conjugated catalyst (GCC) active sites featuring aryl-pyridinium moieties (N+-GCC). ORR catalysis at glassy carbon surfaces modified with N+-GCC fragments displays near-first-order dependence in O2 partial pressure and near-zero-order dependence on electrolyte pH. Tafel analysis suggests an equilibrium one-electron transfer process followed by a rate-limiting chemical step at modest overpotentials that transitions to a rate-limiting electron transfer sequence at higher overpotentials. Finite-cluster computational modeling of the N+-GCC active site reveals preferential O2 adsorption at electrophilic carbons alpha to the pyridinium moiety. Together, the experimental and computational data indicate that ORR proceeds via a proton-decoupled O2 activation sequence involving either concerted or stepwise electron transfer and adsorption of O2, which is then followed by a series of electron/proton transfer steps to generate water and turn over the catalytic cycle. The introduced mechanistic model serves as a roadmap for the bottom-up synthesis of highly active N-doped carbon ORR catalysts.},
doi = {10.1021/acscatal.7b03086},
journal = {ACS Catalysis},
number = 11,
volume = 7,
place = {United States},
year = {2017},
month = {9}
}

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