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

Ricke, Nathan D., Murray, Alexander T., Shepherd, James J., Welborn, Matthew G., Fukushima, Tomohiro, Van Voorhis, Troy, Surendranath, Yogesh (2017) Molecular-Level Insights into Oxygen Reduction Catalysis by Graphite-Conjugated Active Sites. ACS Catalysis, 7 (11). pp. 7680-7687. ISSN 2155-5435. (doi:10.1021/acscatal.7b03086) (KAR id:67424)

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https://dx.doi.org/10.1021/acscatal.7b03086

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 (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 \(O_2\) 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 \(O_2\) adsorption at electrophilic carbons alpha to the pyridinium moiety. Together, the experimental and computational data indicate that ORR proceeds via a proton-decoupled \(O_2\) activation sequence involving either concerted or stepwise electron transfer and adsorption of \(O_2\), 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.

Item Type: Article
DOI/Identification number: 10.1021/acscatal.7b03086
Uncontrolled keywords: N-doped carbon, oxygen reduction, electrocatalysis, mechanistic studies, density functional theory
Subjects: Q Science > QD Chemistry
Divisions: Faculties > Sciences > School of Physical Sciences
Depositing User: Alexander Murray
Date Deposited: 27 Jun 2018 11:07 UTC
Last Modified: 13 Jan 2020 12:18 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/67424 (The current URI for this page, for reference purposes)
Murray, Alexander T.: https://orcid.org/0000-0002-7914-8205
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