Visible-light photocatalytic oxidation of gas-phase Hg0 by colored TiO2 nanoparticle-sensitized Bi5O7I nanorods: Enhanced interfacial charge transfer based on heterojunction

A series of colored TiO2/Bi5O7I composites were successfully fabricated. The physicochemical properties of the as-prepared TiO2/Bi5O7I heterostructures were investigated by XRD, SEM, TEM, HRTEM, FT-IR, BET, UV-vis DRS, XPS and PL characterization. The characterization indicates that colored TiO2 nanoparticles are tightly anchored to the Bi5O7I nanorods to form heterojunctions. The photocatalytic activity of the sample was examined by photocatalytic oxidation of gas-phase Hg-0 under visible-light irradiation. The results show that TiO2/Bi5O7I composites exhibits highly enhanced visible light photocatalytic activity compared to pure Bi5O7I. Hg-0 removal rate of TiO2/Bi5O7I composite is up to 89%. Compared with the pure Bi5O7I, the as-prepared composite photocatalyst enhanced the visible light absorption and increased the specific surface area. More importantly, the heterostructure formed in the composite effectively promotes the charge transfer, ultimately improves the photocatalytic activity. Meanwhile, the cyclic experiments were performed to confirm the stability of TiO2/ Bi5O7I composites. The influence of various flue gas components (O-2, NO and SO2) on the performance of photocatalytic removal of Hg-0 was studied. Based on characterization and experiments, the reasonable charge transfer and photocatalytic reaction mechanism were proposed.