Photophysical and photocatalytic properties of the visible-light-driven photocatalysts BaIn0.5Nb0.5O3, BaCo1/3Nb2/3O3 and BaNi1/3Nb2/3O3

A new series of the visible-light-driven photocatalysts BaIn0.5Nb0.5O3, BaCo1/3Nb2/3O3 and BaNi1/3Nb2/3O3 with ABO(3) perovskite structure has been developed by controlling their crystal and electronic structure. In these photocatalysts the B site is randomly occupied by two kinds of cations. They were characterized by X-ray diffraction, scanning electron microscopy, UV-Vis diffuse reflectance spectroscopy, Raman scattering spectroscopy and the photocatalytic activity measurements under UV and visible light irradiation (lambda > 420 nm), respectively. Under the octahedral crystal field, the 3d orbitals split into t(2g) and e(g) orbitals. The split t(2g) or e(g) orbitals in the photocatalysts BaCo1/3Nb2/3O3 and BaNi1/3Nb2/3O3 acts as a new valence band instead of the O 2p orbital, while in BaIn0.5Nb0.5O3 the In 5s orbital acts as a lower conduction band. All the photocatalysts absorb visible light photons obviously, which can be ascribed to their unique electronic structures. Under visible light irradiation (lambda > 420 nm), these photocatalysts show obvious photocatalytic activities in evolving H-2 from CH3OH/H2O solution with Pt co-catalyst.