Visible Light Response of Wide Band Gap Semiconductor Photocatalysts by Doping of Transition Metal Ions. Aiming at Water Splitting.

Abstract

New visible-light-driven photocatalysts have been developed by doping of transition metal ions into photocatalyst materials, TiO2, SrTiO3, and ZnS, which have wide band gaps. TiO2 co-doped with chromium and antimony ions and Pt-loaded SrTiO3 co-doped with chromium and antimony or tantalum ions evolved O2 and H2 from water containing sacrificial reagents, respectively. In these photocatalysts, the visible-light-responses were due to the electron donor levels in the band gaps formed by doped transition metal ions. Moreover, maintaining of the charge balance in the titanate photocatalysts by co-doping of Cr3+ with high-valent ions (Sb5+ and Ta5+) played an important role for suppression of recombination between photogenerated electrons and holes, resulting in showing high photocatalytic activities. On the other hand, transition metal ion-doped ZnS photocatalysts efficiently evolved H2 from the water containing sacrificial reagents even without Pt co-catalysts.