A novel photocatalytic mechanism of volatile organic compounds degradation on BaTiO3 under visible light: Photo-electrons transfer from photocatalyst to pollutant

Wide bandgap semiconductors are typically activated under ultraviolet (UV) light irradiation for volatile organic compounds (VOCs) degradation. However, our previous study discovered that certain VOCs can interact with some wide bandgap semiconductors, formatting an intermediate bandgap between the VOCs and the conduction band of wide bandgap semiconductor, thus inducing visible light activation of the system, and photo-generated electrons are excited by visible light and transferred from the VOCs to the conduction band of semiconductor. In this work, BaTiO3, traditionally is not active under visible light irradiation, however showed degradation rates of 100% and 20% for styrene and toluene under visible light, respectively. Density functional theory (DFT) calculations indicate that the adsorption of styrene or toluene on the BaTiO3 surface reduces its bandgap from 2.93 eV to 1.36 eV and 2.26 eV, respectively. The intermediate bandgap in this system is primarily formed by the valence band of BaTiO3 and the VOCs, and indicating that photo-generated electrons directly transfer from BaTiO3 to the VOCs under visible light, inducing degradation reactions of VOCs, i.e., this work discovered a new transfer pathway of photo-electrons direct from the valence band of BaTiO3 to VOCs, while photo-electrons are from VOCs to the conductive band of wide-bandgap semiconductors in our previous work.