Band structure and photocatalytic properties of perovskite-type compound Ca2NiWO6 for water splitting

An oxide semiconductor Ca2NiWO6, with double-perovskite crystal structure, was synthesized by solid-state reaction method. The compound Ca2NiWO6 was characterized by X-ray diffraction, UV–visible diffuse reflectance, and photoluminescence. The photocatalytic properties of the compound for water splitting were investigated under UV and visible light irradiation. The results showed H2 evolution was not observed over the compound under visible light irradiation (λ>420 nm) with a 300 W xenon arc lamp when using methanol (CH3OH) as electron donor, although the compound was responsive to visible light region. Based on the experimental results, a possible band structure was proposed through theoretical calculation of the electronic structure by using the full potential-linearized augmented plane wave (F-LAPW). The band structure and photocatalytic properties were attributed to the special crystal and electronic structures. Due to the oxygen vacancies in the compound, which worked as electron–hole recombination centers, the photocatalytic activity of the compound was low.