Electronic structure and photocatalytic properties of Ag-La codoped CaTiO3

Recently, ion-codoped semiconductor systems have been employed as photocatalysts with the objective of improving their photocatalytic activities under visible-light irradiation. In this paper, the effects of monovalence silver ion and trivalence lanthanum codoping into the photocatalytic activity of CaTiO3 powder for overall water splitting were studied experimentally and theoretically. Pure and Ag-La codoped CaTiO3 powder, prepared by sol-gel method which is assisted with ultrasonic technique for the first time, is further characterized by ultraviolet-visible (UV-vis) absorption spectroscopy. The UV-vis spectra indicate that the Ag+-La3+ ions doping not only enhanced the photocatalytic activity under ultraviolet-visible (lambda > 300 nm) light irradiation but also made the photocatalysts have visible light (lambda > 400 nm) response. Photocatalytic activity of codoped CaTiO3 powder for hydrogen evolution under UV light is increased dramatically than that of pure CaTiO3 powder when the doping amount is 3 mol%. The electronic structures of pure and codoped CaTiO3 were investigated using density functional theory (DFT). The results of DFT calculation illuminate that the visible-light absorption bands in the Ag-La codoped CaTiO3 catalyst are attributed to the band transition from the Ag 4d5s to the O 2p + Ti 3d hybrid orbital. (C) 2011 Elsevier B.V. All rights reserved.