Electronic structure and photocatalytic properties of Ag-La codoped CaTiO ₃

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 CaTiO ₃ powder for overall water splitting were studied experimentally and theoretically. Pure and Ag-La codoped CaTiO ₃ 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 ⁺-La ³⁺ ions doping not only enhanced the photocatalytic activity under ultraviolet-visible (λ > 300 nm) light irradiation but also made the photocatalysts have visible light (λ > 400 nm) response. Photocatalytic activity of codoped CaTiO ₃ powder for hydrogen evolution under UV light is increased dramatically than that of pure CaTiO ₃ powder when the doping amount is 3 mol%. The electronic structures of pure and codoped CaTiO ₃ were investigated using density functional theory (DFT). The results of DFT calculation illuminate that the visible-light absorption bands in the Ag-La codoped CaTiO ₃ catalyst are attributed to the band transition from the Ag 4d5s to the O 2p + Ti 3d hybrid orbital.