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

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.

Reactivity Determinants in Electrodeposited Cu Foams for Electrochemical CO Reduction.

CO reduction is of significant interest for the production of nonfossil fuels. The reactivity of eight Cu foams with substantially different morphologies was comprehensively investigated by analysis of the product spectrum and in situ electrochemical spectroscopies (X-ray absorption near edge structure, extended X-ray absorption fine structure, X-ray photoelectron spectroscopy, and Raman spectroscopy). The approach provided new insight into the reactivity determinants: The morphology, stable Cu oxide phases, and *CO poisoning of the H formation reaction are not decisive; the electrochemically active surface area influences the reactivity trends; macroscopic diffusion limits the proton supply, resulting in pronounced alkalization at the CuCat surfaces (operando Raman spectroscopy).

Spectroscopic identification of active sites for the oxygen evolution reaction on iron-cobalt oxides.

The emergence of disordered metal oxides as electrocatalysts for the oxygen evolution reaction and reports of amorphization of crystalline materials during electrocatalysis reveal a need for robust structural models for this class of materials. Here we apply a combination of low-temperature X-ray absorption spectroscopy and time-resolved in situ X-ray absorption spectroelectrochemistry to analyze the structure and electrochemical properties of a series of disordered iron-cobalt oxides. We identify a composition-dependent distribution of di-μ-oxo bridged cobalt-cobalt, di-μ-oxo bridged cobalt-iron and corner-sharing cobalt structural motifs in the composition series.