On the active sites for the oxygen reduction reaction catalyzed by graphene-based materials

At the heart of the mechanism and efficiency of oxygen reduction is the identification of active sites in graphene-based electrocatalysts ranging from carbon blacks to heat-treated phthalocyanines. Distinction between the transfer of two or four electrons points to O2 dissociation as the essential m...

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Bibliographic Details
Published in:Carbon (New York) 2020-01, Vol.156, p.389-398
Main Authors: Radovic, Ljubisa R., Salgado-Casanova, Adolfo J.A., Mora-Vilches, Camila V.
Format: Article
Language:English
Subjects:
Adsorption
Carbon
Density distribution
Electrocatalysis
Electrocatalysts
Electron density
Electron transfer
Graphene
Heat treatment
Oxidation
Oxygen
Oxygen reduction reactions
Transition metals
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Summary:At the heart of the mechanism and efficiency of oxygen reduction is the identification of active sites in graphene-based electrocatalysts ranging from carbon blacks to heat-treated phthalocyanines. Distinction between the transfer of two or four electrons points to O2 dissociation as the essential mechanistic clue; here we examine this issue by exploiting the analogy with carbon oxidation, where production of CO vs. CO2 has long been a crucial point. We compare our computational results with experimental evidence on the behavior of graphene as well as its N-, B- and transition-metal-doped counterparts. Electron transfer is revealed to occur readily through a carbene-type site upon oxygen surface rearrangement. Whether adsorbed O2 dissociates depends on proton transfer occurring before or after the stabilization of a peroxy intermediate; this in turn depends on electron density distribution at and around the active site. A good correlation exists between spin density at the active site and O2 adsorption energy. [Display omitted]
ISSN:0008-6223
1873-3891
DOI:10.1016/j.carbon.2019.09.059