Polymerizable complex synthesis of BaZr1-xSnxO3 photocatalysts: Role of Sn4+ in the band structure and their photocatalytic water splitting activities

The effects of Sn substitution for Zr on photocatalytic water splitting activity of BaZrO3 were investigated experimentally and theoretically. Hydrogen and oxygen were produced from pure water over BaZr1-xSnxO3 photocatalysts without the assistance of any cocatalysts under ultraviolet light irradiation, and the highest gases evolution rate (138 mu mol h(-1) for H-2 and 37 mu mol h(-1) for O-2) was observed over 0.2 g BaZr0.7Sn0.3O3 photocatalyst. Density functional theory calculations of BaZr1-xSnxO3 (x = 0, 0.25, and 0.5) indicate that, as Sn concentration increases, the contribution of Sn 5s orbitals to the bottom of the conduction band gradually becomes dominant and the band gap type of BaZr1-xSnxO3 was switched from indirect to direct. The participation of the Sn 5s orbitals in the electronic structure of BaZrO3 not only reduces the energy band gap but also affects the charge carrier excitation process, thus resulting in the different H-2 production rate.