A facile approach to synthesize CoO-Co3O4/TiO2 NAs for reinforced photoelectrocatalytic water oxidation

Abstract

Photoelectrocatalytic (PEC) water splitting technology is used to convert solar energy into hydrogen energy, and has the potential to alleviate energy crisis problem. TiO2 nanowire arrays (NAs), as a promising PEC photoanode, have the advantages of low cost and stable mechanical properties. However, due to its wide energy band, poor conductivity, and slow carrier transfer kinetics, modifying TiO2 NAs with metal is a feasible way to achieve high PEC performance, especially cobalt-based compounds. Different from the fussy and polluted synthesizing methods, here, we use a facile method to successfully load Co3O4 and CoO mixtures on TiO2 NAs. A series of characterization methods are conducted to study the morphology, structure, and PEC water oxidation performance. It is found that the photocurrent density of the obtained CoO-Co3O4/TiO2 photoelectrode is enhanced and good stability can be kept up for 13 h or more. The prominent reason for enhanced PEC performance of CoO-Co3O4/TiO2 NAs is that loading CoO and Co3O4 can increase the light absorption, reduce the charge transfer resistance, and improve the charge separation efficiency of TiO2 NAs. Our work introduces an alternative designing way to load both of CoO and Co3O4 on photoelectrode in a particularly eco-benign way, which provides efficient and stable cobalt-based TiO2 photoanodes, and it can be applied to wider research fields, such as solar cells and photo-responsive devices.