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

Nathan D Ricke; Alexander T Murray; James J Shepherd; Matthew G Welborn; Tomohiro Fukushima; Troy Van Voorhis; Yogesh Surendranath

doi:10.1021/acscatal.7b03086

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

Journal article

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

Nathan D Ricke, Alexander T Murray, James J Shepherd, Matthew G Welborn, Tomohiro Fukushima, Troy Van Voorhis and Yogesh Surendranath

ACS Catalysis, Vol.7(11), pp.7680-7687

2017

DOI: 10.1021/acscatal.7b03086

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Abstract

Using a combination of experimental and computational investigations, we assemble a consistent mechanistic model for the oxygen reduction reaction (ORR) at molecularly well-defined graphite-conjugated catalyst ( ) active sites featuring aryl-pyridinium moieties ( ). ORR catalysis at glassy carbon surfaces modified with fragments displays near-first-order dependence in O 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 active site reveals preferential O adsorption at electrophilic carbons alpha to the pyridinium moiety. Together, the experimental and computational data indicate that ORR proceeds via a proton-decoupled O activation sequence involving either concerted or stepwise electron transfer and adsorption of O , which is then followed by a series of electron/proton transfer steps to generate water and turn over the catalytic cycle. The proposed mechanistic model serves as a roadmap for the bottom-up synthesis of highly active N-doped carbon ORR catalysts.

Details

Title: Subtitle: Molecular-Level Insights into Oxygen Reduction Catalysis by Graphite-Conjugated Active Sites
Creators: Nathan D Ricke
Alexander T Murray
James J Shepherd
Matthew G Welborn
Tomohiro Fukushima
Troy Van Voorhis
Yogesh Surendranath
Resource Type: Journal article
Publication Details: ACS Catalysis, Vol.7(11), pp.7680-7687
DOI: 10.1021/acscatal.7b03086
ISSN: 2155-5435
eISSN: 2155-5435
Grant note: DOI: 10.13039/100006151, name: Basic Energy Sciences, award: DE-SC0014176
Language: English
Date published: 2017
Academic Unit: Chemistry
Record Identifier: 9983985834102771

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