InVO4-sensitized TiO2 photocatalysts for efficient air purification with visible light

A visible-light-driven InVO4/TiO2 mesoporous photocatalyst was prepared by a sol–gel method. The catalyst was characterized by powder X-ray diffraction (XRD), nitrogen adsorption–desorption, transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy, X-ray photoelectron spectra (XPS), ultraviolet photoelectron spectra (UPS), and spin-trapping electron paramagnetic resonance (EPR). Photocatalytic activity of the sample was evaluated by the degradation of volatile organic compounds (VOCs) in air under visible light irradiation (450 nm ≤ λ ≤ 900 nm). Results revealed that the addition of InVO4 leaded to the visible light response up to ∼540 nm for InVO4/TiO2. Moreover, upon visible light irradiation, some superoxide radical anions, such as O2− and OH radicals, were generated on InVO4/TiO2, leading to the decomposition of VOCs. The high photocatalytic activity towards VOCs (e.g. benzene) was still maintained in the cycle experiments, and the turnover numbers recorded within 12 h work out to be 11.8 mol (produced CO2) and 6.2 mol (degraded C6H6) per mol catalyst. Deactivation of the photocatalyst was not observed during the cycle experiments. It has been confirmed that InVO4/TiO2 photocatalyst could be activated by visible light due to the existence of the InVO4. Based on the energy-band levels of InVO4 and TiO2, a photosensitization mechanism of InVO4/TiO2 is proposed.