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 H₂ 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 H₂ evolution rate in comparison with individual materials. The overall band structure, charge carrier excitation, separation, and transportation and the redox reactions for H₂ and O₂ 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.