Application of cobalt oxide to the water oxidation reaction by modification and complex formation

Abstract

There have been many efforts to obtain increased active sites in metal oxides to achieve a high performance in many catalyst reactions, including photocatalytic water oxidation. Reducing the size scale and introducing defect generation in the nanostructure leads to remarkably enhancement of both the reaction surface area and the stimulated catalytic active sites. We demonstrate with ex-situ STEM, XPS, BET surface area, EXAFS, UV-vis analyses that cobalt oxide through redox process leads to the formation of porous cobalt oxide. Indeed, porous cobalt oxide has high efficiency with more than 20-folds for photocatalytic water oxidation in a $Ru(bpy)_3Na_2S_2O_8$ system compared to that of bulk $Co_3O_4$. In addition, the $Co_3O_4$ composites with graphene fabricated and modified via electrochemical reactions showed higher efficiency than other cobalt oxide composite materials.