Band structure and photocatalytic properties of perovskite-type compound Ca2NiWO6 for water splittin.pdf

Band structure and photocatalytic properties of perovskite-type compound Ca2NiWO6 for water splitting Dunfang Li a,b, Jing Zheng a,b, Zhigang Zou a,b,* a Eco-Materials and Renewable Energy Research Center (ERERC), Nanjing University, Nanjing 210093, People’s Republic of China b Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, People’s Republic of China Received 8 August 2005; accepted 31 October 2005 Abstract 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 (lO420 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. q 2005 Elsevier Ltd. All rights reserved. Keywords: A. Semiconductors; D. Crystal structure; D. Electrical properties; D. Optical properties1. Introduction Photocatalytic production of H2 and O2 from water splitting with oxide semiconductors has increasingly received interest from the view of the utilization of solar energy due to energy and environmental issues [1–3]. Up to now, extensive efforts have been made to develop new semiconductor photocatalysts to reveal