Photocatalytic water splitting with the Cr-doped Ba2In2O5/In2O3 composite oxide semiconductors

The Cr-doped Ba2In2O5/In2O3 (C-BIO) oxide semiconductors synthesized by a solid-state reaction method were found to be a novel composite photocatalyst system with enhanced activity for water splitting. The C-BIO powder samples were characterized with X-ray diffraction (XRD), UV-vis diffuse reflectance spectrometry, energy dispersive spectrometry (EDS), and high-resolution transmission electron microscopy (HRTEM). The photocatalytic activities of Pt- or NiO-loaded C-BIO and individual precursor materials were evaluated by H-2 evolution from aqueous CH3OH solution under visible light and by pure water splitting under UV light irradiation, respectively. It was found that the composite C-BIO showed a higher H-2 evolution rate in comparison with individual materials. The overall band structure, charge carrier excitation, separation, and transportation and the redox reactions for H-2 and O-2 evolution in the C-BIO system are discussed in relation to the photophysical and photocatalytic properties, and some guidelines are suggested for designing efficient composite semiconductor photocatalysts for water splitting.