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 H-2 evolution was not observed over the compound under visible light irradiation (lambda > 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. (c) 2005 Elsevier Ltd. All rights reserved.