Crystal facet engineering for production of TiO2/WO3photoelectrodes with superior energy storage capacity

Abstract

WO3 thin films with (002)-preferred orientation showing superior electron storage capacity were prepared using a vacuum evaporation system. The electron storage capacity of the WO3 photoelectrode can be improved by controlling the crystallographic orientation of the WO3 crystals. In photoelectrochemical water splitting, the TiO2/WO3 photoelectrode exhibited a significantly higher increment in current density than the pristine WO3 photoelectrode. The charging and discharging capacities of the preferentially oriented WO3 layer can be derived in full value to introduce a TiO2 layer with a porous morphology. Moreover, because a difference in the crystal facet results in a slight change in the energy of the valence and conduction bands, it can be speculated that better separation of electron-hole pairs is achieved, leading to exposure of the (002) dominant crystal facet of WO3.