Mitsutake Oshikiri
National Institute for Materials Science, Japan
Title: Theoretical investigation on heterogeneous photocatalytic systems containing metal oxide and aqueous solution
Biography
Biography: Mitsutake Oshikiri
Abstract
To date, in the field of photo-catalysis using metal oxide inorganic materials, the most extensively studied systems have been the TiO2-based materials. However, the efficiency in decomposing water molecule and producing oxygen and hydrogen upon sun light irradiation is still low. In an attempt at overcoming these limitations, photocatalytic properties of quite a few metal oxides different from TiO2 have been explored. Materials based on vanadate such as BiVO4, InVO4 and YVO4 were among them and might represent a promising alternative to TiO2-based systems. Indeed, the BiVO4 can produce oxygen by photo-catalysis up to wavelengths of about 520 nm if the sacrificial reagent AgNO3 is added. However, no hydrogen generation has been reported to date. On the other hand, InVO4 shows hydrogen evolution in the visible wavelength range (from ultra violet (UV) to 600 nm) even from common liquid water, but it seems impossible to get oxygen. In case of the YVO4 system, it has been shown to possess surprisingly high efficiencies in both O2 and H2 productions in conjunction with the co-catalyst NiOx. But the difficulty stems from its activity, which seems to be limited just to the UV region. The reason why these material systems indicate such contrastive photo catalytic properties was not cleared from a point of view of the electronic structure features on the bulk crystals of these materials, however, the electronic structures investigated by using inhomogeneous models including water and solid metal oxide photocatalysts equilibrated at room temperature obtained by applying first principles molecular dynamical simulations are now unraveling the mysteries. In this conference, I would like to introduce my research activities on metel oxide photocatalysts in this decade.