Adsorption-assisted photocatalytic activity of nitrogen and sulfur codoped TiO2 under visible light irradiation

Abstract

Applying post thermal treatment on the doped TiO₂ at high temperature is mostly regarded as an indispensable process, although it has negative effects on the photocatalytic activity of doped TiO₂. Herein, we synthesized the N- and S-codoped TiO₂ (NSTs) with an anatase phase using a simple solvothermal treatment and investigated their visible light photocatalytic activity associated with the thermal behavior of dopants in NSTs. We found that the as-synthesized NST (NST-As) has better visible light photocatalytic activity and adsorptivity than the commercially available P25 and the thermally treated NSTs. The S dopants effectively assist the surface reaction by adsorbing cations of organic dyes on the NST-As surface. The N dopants increase the absorbance at visible light region of NST-As by forming a delocalized state at the band gap of NST-As. However, the photocatalytic activity of NSTs gradually weakens with the post thermal treatment, because S dopants on the NST-As surface are transformed from sulfide to sulfate during the thermal treatment and N dopants move out during the crystallization of TiO₂. The adsorption-assisted photocatalytic activity of NST-As under visible light irradiation is an attractive feature for environmental and photonic technologies.