Tailored visible-light driven anatase TiO2 photocatalysts based on controllable metal ion doping and ordered mesoporous structure

Abstract

Visible-light driven ordered mesoporous metal ion doped anatase TiO₂ photocatalysts were synthesized via a hard-template chemical route. The effects of metal ion doping on the band energy level, surface area, pore volume, pore diameter, and photocatalytic properties of the ordered mesoporous anatase TiO₂ were systematically investigated. X-Ray photoelectron spectra and UV-vis absorption spectra indicate that the W and Mn ions enter into the lattice of anatase TiO₂ in the presence of W⁶⁺ and Mn³⁺/Mn⁴⁺, resulting in a band gap transition with a red shift from the ultraviolet to the visible range, preventing the recombination rate of electron-hole pairs, therefore the photocatalytic activity can be greatly enhanced in the visible region. There exists an optimal doping level of 5 mol% W and 0.5 mol% Mn, respectively, with 95% MB and 82% MB being photocatalytically decomposed within 70 min under the visible light for 5% W and 0.5% Mn doped mesoporous anatase TiO₂, respectively. Importantly, W ion doped TiO₂ displays much higher photocatalytic efficiency than Mn ion doped TiO₂, which can be attributed to the presence of much higher Lewis surface acidity of W⁶⁺ doped TiO₂ surface with a higher affinity for chemical species having unpaired electrons than Mn doped TiO₂. In addition, the W doping induced grain refinement, highly crystalline state, large surface area and large pore size additionally contribute to the improved photocatalytic activity of the mesoporous W-doped TiO₂ samples. The enhanced ability to absorb visible light makes the ordered mesoporous metallic ion doped TiO₂ an effective photocatalyst for solar-driven applications.