Defect Evolution Enhanced Visible-Light Photocatalytic\nActivity in Nitrogen-Doped Anatase TiO₂ Thin Films

Abstract

Doping\nnitrogen (N) into TiO₂ is one of the promising\nways to extend the photocatalytic activity into the visible-light\nrange, enabling to harvest more solar energy. In this study, we realize\na high concentration of N incorporated into the anatase TiO₂ films on indium tin oxide substrates. The band gap of TiO₂ with a high N substitutional doping is reduced to 1.91 eV, showing\na much improved photocatalytic reactivity, as supported by the degrading\nmethyl orange solution radiated with visible light. First-principles\ncalculations further suggest that the form of dominant defects evolves\nfrom the substitution of N (N_O) to the coexistence of N_O and oxygen vacancies (O_V) when the N-doping concentration\nis increased, which leads to the reduction of band gap in the visible-light\nrange and more delocalized charge distribution. Our results demonstrate\na novel synthesis route that can realize a high concentration of N\nsubstitutional doping in TiO₂ films and provide an improved\nunderstanding of enhanced visible-light photocatalytic performance\nof N-doped TiO₂.