Photocatalytic Activity of SrTiO3 Codoped with Nitrogen and Lanthanum under Visible Light Illumination

Abstract

Yellow SrTiO₃ powders codoped with nitrogen and lanthanum (STO:N,La) were studied as visible light photocatalysts. The crystal phase of STO:N,La exhibited a pure perovskite phase, and O and Sr sites atoms were substitutionally doped with N and La atoms, respectively. The first principle calculation of STO:N,La indicated that the edge of the N(2p) band is situated above the valence band, which consisted of O(2p) orbitals, and the La orbitals did not exist in the band gap of SrTiO₃. STO:N,La exhibited a higher oxidation activity of gaseous 2-propanol under vis illumination than SrTiO₃ doped only with nitrogen (STO:N). The high activity of STO:N,La was due to the decrease in the oxygen vacancies, which acted as electron−hole recombination centers, because codoping with La³⁺ and N^3- ions maintained the charge balance. The optimum doping density of N and La for visible light activity was 0.5%, and STO:N,La(0.5%) had an activity under UV illumination similar to pure SrTiO₃.