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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 Li<sub>2</sub>Co<sub>2</sub>O<sub>4</sub> 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]

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