\Abstract-Several new photocatalysts for overall water splitting are described. Under UV light irradiation (270 nm), La-doped NaTaO3 modified with NiO decomposed water into H2 and O2 with extremely high quantum efficiency. Under an optimized condition, the apparent quantum efficiency, which was estimated with numbers of irradiated photons and evolved H2 molecules, reached 56%. New stable photocatalytic materials containing elements with d(10) electronic configuration such as In3+, Sn4+ and Sb5+ were developed for overall water splitting. Some mesoporous oxides were proved to be effective photocatalysts. (Oxy)nitrides of some early transition metals, i.e., Ta, Nb and Ti, were found to be stable materials having potentials for H2 and O-2 evolutions under visible light irradiation (≤ 600 nm). The electronic structures of these photocatalysts are also discussed based on DFT calculation.