Crystal facet engineering for production of TiO2/WO3 photoelectrodes 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.