A visible-light-induced two-step overall water splitting was achieved by combining two types of photocatalysts prepared by introducing foreign elements into the identical mother structure with a controlled electronic band structure. Strontium titanate (SrTiO 3 ) was selected as the mother structure and was doped with either vanadium (and sodium) or rhodium to introduce visible light sensitivity. By utilizing these two types of SrTiO 3 -based photocatalysts, simultaneous liberation of hydrogen (H 2 ) and oxygen (O 2 ) with a molar ratio of ∼2:1 was achieved in the presence of iodate ion (IO 3 − )/iodide ion (I −

We investigated the ability of β-iron silicide (β-FeSi2) to serve as a hydrogen (H2)-evolution photocatalyst due to the potential of its conduction band bottom, which may allow thermodynamically favorable H2 evolution in spite of its small band-gap of 0.80 eV. β-FeSi2 had an apparent quantum efficiency for H2 evolution of ∼24% up to 950 nm (near infrared light), in the presence of the dithionic acid ion (S2O6(2-)) as a sacrificial agent. It was also sensitive to infrared light (>1300 nm) for H2 evolution.

Visible light-sensitive photocatalyst was developed by combining n-type silicon (n-Si) and tungsten trioxide (WO 3 , n-Si/WO 3 ), yielding an ohmic contact in between. In this system, the ohmic contact acted as an electron-and-hole mediator for the transfer of electrons and holes in the conduction band (CB) of WO 3 and in the valence band (VB) of n-Si, respectively. Utilizing thusconstructed n-Si/WO 3 , the decomposition of 2-propanolto CO 2 via acetone was achieved under visible light irradiation, by the contribution of holes in the VB of WO 3 to decompose 2-propanol and the consumption of electrons in the CB of n-Si to reduce O 2 .