Promotion of Visible Light Response of Anatase TiO2 by S-F-codoping

Abstract:

Understanding the band gap narrowing of anatase TiO₂induced by S-F-codoping is attractive and significant for their potential applications in renewable energy by converting sunlight to electricity or fuels.

In this work, we used density functional theory calculations to investigate the electronic structures of anatase TiO₂ and further explored the mechanism of band gap narrowing of anatase TiO₂ induced by S-F-codoping. It was found the valence and conduction bands of F-doped TiO₂, with the doped F concentration of 1.19 %, consisted of the electrons of O2p and Ti3d.The small amount of electrons of F2p didn't change the band gap of TiO₂. For S-F-codoped TiO₂, with the same S, F concentration of 1.19 %, the upper valence appeared doping states due to additional S-doping, and the transition of S3p to the conduction band was the reason for the redshift of S-F-TiO₂ compared with undoped TiO₂.Results indicated that the S-F-codoped anatase TiO₂is an intrinsic semiconductor with a band gap of 1.80 eV.

Experimental results exhibited a figure-of-merit for photoelectrochemical (PEC) catalysis of S-F-codoped anatase TiO₂ in visible light region. The removal efficiency of Acid Orange 7 reached 98.1 % in 180 min under visible light irradiation (I₀ = 0.6 mW/cm², λ＞400 nm) with a bias voltage of 0.25 V. The incident photocurrent intensity was about 20.0 μA/cm²measured online by an electrochemical station.