Photophysical and Photocatalytic Properties of MIn0.5Nb0.5O3 (M = Ca, Sr, and Ba)

New photocatalysts MIn 0.5 Nb 0.5 O 3 (M = Ca, Sr, and Ba) with the ABO 3 type perovskite structure in which B sites are occupied by In 3+ or Nb 5+ ions randomly in a charge-balanced manner were synthesized. They were characterized by structural analysis, diffuse reflectance spectroscopy, and photocatalytic activity measurement in evolving H 2 and O 2 from pure water with cocatalysts Pt and NiO x under UV and visible light irradiation (λ > 420 nm), respectively. It is suggested that the conduction bands of these photocatalysts are composed of In 5s and Nb 4d levels, and the valence bands are composed of O 2p levels. With the decrease of the ionic radius in the A site, the CaIn 0.5 Nb 0.5 O 3, SrIn 0.5 Nb 0.5 O 3, and BaIn 0.5 Nb 0.5 O 3 photocatalysts show different photocatalytic activities. Under UV light irradiation, the BaIn 0.5 Nb 0.5 O 3 photocatalyst powder with cocatalyst NiO x split pure water into H 2 and O 2 in a nearly stoichiometric ratio. Under visible irradiation, all of these photocatalysts show obvious photocatalytic activity in evolving H 2 from pure water with cocatalyst NiO x .