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Voltage- and time-dependent valence state transition in cobalt oxide catalysts during the oxygen evolution reaction.

ABSTRACT: The ability to determine the electronic structure of catalysts during electrochemical reactions is highly important for identification of the active sites and the reaction mechanism. Here we successfully applied soft X-ray spectroscopy to follow in operando the valence and spin state of the Co ions in Li₂Co₂O₄ under oxygen evolution reaction (OER) conditions. We have observed that a substantial fraction of the Co ions undergo a voltage-dependent and time-dependent valence state transition from Co³⁺ to Co⁴⁺ accompanied by spontaneous delithiation, whereas the edge-shared Co-O network and spin state of the Co ions remain unchanged. Density functional theory calculations indicate that the highly oxidized Co⁴⁺ site, rather than the Co³⁺ site or the oxygen vacancy site, is mainly responsible for the high OER activity.

SUBMITTER: Zhou J

PROVIDER: S-EPMC7181785 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature

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Voltage- and time-dependent valence state transition in cobalt oxide catalysts during the oxygen evolution reaction.

Zhou Jing J Zhang Linjuan L Huang Yu-Cheng YC Dong Chung-Li CL Lin Hong-Ji HJ Chen Chien-Te CT Tjeng L H LH Hu Zhiwei Z

Nature communications 20200424 1

The ability to determine the electronic structure of catalysts during electrochemical reactions is highly important for identification of the active sites and the reaction mechanism. Here we successfully applied soft X-ray spectroscopy to follow in operando the valence and spin state of the Co ions in Li2Co2O4 under oxygen evolution reaction (OER) conditions. We have observed that a substantial fraction of the Co ions undergo a voltage-dependent and time-dependen ...[more]

PMID: 32332788

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