Efficient development of Type-II TiO2 heterojunction using electrochemical approach for an enhanced photoelectrochemical water splitting performance

Type-II-heterojunction TiO2 nanorod arrays (NAs) are achieved by a combination of reduced and pristine TiO2 NAs through a simple electrochemical reduction. The heterojunction-structured TiO2 NAs exhibit an enhanced photo-efficiency, with respect to those of pristine TiO2 NAs and completely reduced black TiO2. The improved efficiency can be attributed to a synergistic effect of two contributions of the partially reduced TiO2 NAs. The light absorption is significantly increased, from the UV to the visible spectrum. Moreover, the type II structure leads to enhanced separation and transport of the electrons and charges. The proposed electrochemical approach could be applied to various semiconductors for a control of the band structure and improved photoelectrochemical performance.