On the surface chemistry and the reuse of sulfur-doped TiO2 films as photocatalysts

Highlights: • S–TiO₂ catalysts obtained under H₂S atmosphere at low temperature are highly efficient. • SO₄²⁻ was formed on the films surface, indicating the substitution of Ti⁴⁺ by S⁶⁺. • XPS depth profile revealed the cationic diffusion of sulfur by the alternative S-doped method. • S-doped TiO₂ film presented 72.1% of dye degradation under visible light. • S–TiO₂ films exhibit high stability and efficiency around 70% in the first 3 cycles. The surface chemistry and recyclability of sulfur-doped titanium dioxide (TiO₂) films was evaluated. The photocatalysts were grown by metalorganic chemical vapor deposition (MOCVD) at 400 °C. The films were sulfur-doped at 50 °C by using hydrogen sulfide (H₂S) as sulfur source. The photocatalytic behavior of the films was measure by monitoring the methyl orange dye decolorization under visible light for several cycles. The films are formed only for the anatase crystalline phase. The results demonstrated that no structural modifications or significant differences in the morphology of the films occurred after their use. The sulfur-doped TiO₂ films presented good photocatalytic activity, with an efficiency of 72.1% under visible light in its first use. The durability experiments suggest that even with the dye impregnation on the catalyst surface, the photocatalytic activity of the S-doped TiO₂ films remained around 70% in the first 3 cycles, which allows their practical application for water treatment and purification under sunlight.