Modification of NiTiO3 visible light-driven photocatalysts by Nb doping and NbOx heterojunction: Oxygen vacancy in the Nb-doped NiTiO3 structure

Abstract

In this study, two types of niobium-containing NiTiO3 photocatalysts ? Nb-doped NiTiO3 and NbOx/NiTiO3 heterojunction ? were prepared with different Nb contents to enhance photocatalytic activity for dye photodegradation under sunlight irradiation. Nb-doped NiTiO3 exhibited higher photocatalytic activity than pure NiTiO3, whereas the heterojunction of NbOx with NiTiO3 caused a decrease in photocatalytic activity. The incorporation of Nb into the NiTiO3 lattice structure induced the formation of Ti3+ and Nb3+ sites, which considerably increased the number of oxygen vacancies in those photocatalysts; this conclusion was confirmed by the results of X-ray photoelectron spectroscopy. Eventually, the Nb-doped NiTiO3 photocatalyst at the highest Nb content (NT-Nb-10) was transformed into a triple metal oxide phase with the highest surface area and oxygen vacancy. The abundant oxygen vacancy of NT-Nb-10 resulted in the lowest photoluminescence emission intensity, which resulted in the highest apparent photocatalytic reaction rate constant (kapp) of 14.1 min?1 owing to the suppression of the recombination process. The formation of the triple metal oxide phase in this study may allow a potential way to modify low cost visible light-driven NiTiO3 photocatalysts for sustainable photocatalytic application.