TiO₂ composite films on different substrates with enhanced visible light photocatalytic performance

For the sake of improving the photocatalytic performance of TiO₂, we prepared the B/Ag/Fe tridoped TiO₂ films on common glass and stone substrates by the sol–gel method. In this work, the optical absorption, recombination of photogenerated electrons (e⁻) and holes (h[Formula: see text]), crystal types, thermal stability, composition, specific surface area and photocatalytic activity of the modified TiO₂ films were investigated. The results indicated that B/Ag/Fe tridoping not only enhanced the absorption of visible light by TiO₂, but inhibited the recombination of electron–hole (e⁻/h[Formula: see text]) pairs. The tridoping also promoted the formation of anatase and prevented the transformation of anatase to rutile at high temperature. The composite TiO₂ has a large specific surface area, about three times that of pure TiO₂. The photocatalytic activity of the TiO₂ films were evaluated by methyl green (MG) and formaldehyde degradation. In all samples, the B/Ag/Fe tridoped TiO₂ film exhibited the highest degradation rate of MG under both ultraviolet and visible light irradiation. The improvement of photocatalytic performance of TiO₂ films is due to the synergistic effect of the B/Ag/Fe tridoping, which enhances the absorption of visible light and prolongs the lifetime of e⁻/h[Formula: see text] pairs and facilitates transfer of interface charge.