Structural and functional role of anions in electrochemical water oxidation probed by arsenate incorporation into cobalt-oxide materials.

Author(s) Villalobos, J.; González-Flores, D.; Klingan, K.; Chernev, P.; Kubella, P.; Urcuyo, R.; Pasquini, C.; Mohammadi, M.Reza; Smith, R.D.L.; Montero, M.L.; Dau, H.
Journal Phys Chem Chem Phys
Date Published 2019 Jun 21
Abstract

Direct (photo)electrochemical production of non-fossil fuels from water and CO requires water-oxidation catalysis at near-neutral pH in the presence of appropriate anions that serve as proton acceptors. We investigate the largely enigmatic structural role of anions in water oxidation for the prominent cobalt-phosphate catalyst (CoCat), an amorphous and hydrated oxide material. Co([(P/As)O])·8HO served, in conjunction with phosphate-arsenate exchange, as a synthetic model system. Its structural transformation was induced by prolonged operation at catalytic potentials and probed by X-ray absorption spectroscopy not only at the metal (Co), but for the first time also at the anion (As) K-edge. For initially isostructural microcrystals, anion exchange determined the amorphization process and final structure. Comparison to amorphous electrodeposited Co oxide revealed that in CoCat, the arsenate binds not only at oxide-layer edges, but also arsenic substitutes cobalt positions within the layered-oxide structure in an unusual AsO coordination. Our results show that in water oxidation catalysis at near-neutral pH, anion type and exchange dynamics correlate with the catalyst structure and redox properties.

DOI 10.1039/c9cp01754b
ISSN 1463-9084
Citation Villalobos J, González-Flores D, Klingan K, Chernev P, Kubella P, Urcuyo R, et al. Structural and functional role of anions in electrochemical water oxidation probed by arsenate incorporation into cobalt-oxide materials. Phys Chem Chem Phys. 2019;21(23):12485-12493.

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