Construction of TiO2/BiOI1−x Z-scheme heterojunction with iodine vacancy for enhancing photocatalytic oxidation of elemental mercury

The novel TiO2/BiOI1−x Z-scheme heterostructure with iodine vacancy was synthesized by calcination method and applied to photocatalytic removal of gas-phase Hg0. Combining with characterization analysis and DFT calculation results, the existence of iodine vacancy and Z-scheme generated charge-carrier migration paths in the TiO2/BiOI1−x composite were confirmed, and their effects on photocatalytic activity were further discussed. In the TiO2/BiOI1−x composite, the synergistic effect of iodine vacancy and Z-scheme heterojunction improved the migration efficiency of photogenerated charge and retain electrons and holes with high redox capacity, which effectively enhances the photocatalytic activity. The experiment results showed the TiO2/BiOI1−x composite possessed excellent photocatalytic removal efficiency of elemental mercury under influence of the synergistic effect. This study provides a new idea for designing photocatalysts with heterojunction and surface defects to purify environmental pollutants.