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

SUBMITTER: Zhou J 

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

REPOSITORIES: biostudies-literature