Z-scheme heterojunction of flower microsphere Bi_7O_9I_3 surface loaded with gray TiO_2 particles for photocatalytic oxidation of gas-phase Hg~0

摘要

Construction of Z-scheme heterojunctions is an effective means to promote electron-hole separation leading to enhanced catalytic efficiency. In this study, a simple deposition method is used to load gray particles of TiO2 onto flower microsphere of Bi7O9I3 to form a direct Z-scheme heterojunction. The surface morphology, energy bands, structural properties, and optic1dal properties of the prepared composites are characterized through several techniques. The results indicate that by controlling the concentration of TiO2 particles, the properties such as electron-hole separation efficiency, band gap energy, photoresponse range, and specific surface area can be adjusted, and the mass percentage of TiO2 in the best Bi7O9I3/TiO2 composite is obtained as 30%. The obtained composite exhibited an absorption range of 700 nm and Hg-0 removal efficiency of 92.5% under visible light irradiation, which is a great improvement over the characteristics of pure Bi7O9I3. Further, the Hg-0 removal efficiency of the composite is evaluated in simulated flue gas. Finally, based on the characterization results, a reasonable reaction mechanism and electron transport mechanism are proposed.