CuCoOx/BiVO multifunctional catalyst for organics degradation, water oxidation, and O reduction under visible light.

Monoclinic BiVO (BiV) is an excellent photoanode for water oxidation, but it is a poor photocatalyst for organic oxidation due to slow O reduction. Herein we report a 94-fold increased photocatalytic activity of BiV through a surface deposited CuCoOx. The model reaction was phenol degradation in aqueous solution under visible light. CuCoOx, CuOx, and CoOx were prepared in butanol, separately, while CuCoO was prepared in aqueous solution. Solid characterization showed that CuCoO was CuCoO, but CuCoOx was a mixture of CuCoO, CuOx, and CoOx. Notably, the rate of phenol oxidation on CuCoOx/BiV was not only larger than those on Pt/BiV, CuCoO/BiV, CuOx/BiV, and CoOx/BiV, but also larger than the sum of the rates obtained for the latter three. Photoluminescence study revealed that all co-catalysts improved the efficiency of charge separation of BiV, with the trend similar to that for phenol photo-oxidation. Electrochemical study with a BiV film electrode showed that among four co-catalysts, CuOx was the most active for O reduction, CoOx for water oxidation, and CuCoO for water photo-oxidation. According to the measured band edge potentials for semiconductors, a possible charge transfer from BiV to co-catalyst is proposed, including the electron transfer for CuOx/BiV, the hole transfer for CoOx/BiV and CuCoO/BiV, and the sequential electron transfer for CuCoOx/BiV.