The formation of Z-scheme AgI/BiOBr heterojunction and its excellent photocatalytic performance

Photocatalysts with Z-scheme AgI/BiOBr heterojunction were prepared through hydrothermal process combined with in situ co-precipitation. Optimum hydrothermal pH value (pH=4) for synthesizing pure BiOBr was selected by conducting photocatalysis tests. Z-scheme AgI/BiOBr heterojunctions were constructed to enhance the photocatalytic performance. Benefiting from the above two strategies, BAI-5 (pH=4, AgI loading amount 13 wt%) presented the best photocatalytic performance under visible light irradiation. The apparent reaction rate constant in degrading Rhodamine B (RhB) upon BAI-5 reached 0.01801 min-1, which was 5.29 times as that upon the pure BiOBr sample BOB-4 (pH=4). In addition, the property of the catalyst for repeated use was analyzed. After 5 cycles, the photocatalytic efficiency of the catalyst still remained 94%. The major active species were determined and the photocatalytic mechanism was revealed. The introduction of AgI enlarged the absorption range of visible light and facilitated the effective separation and transfer of photogenerated charge carriers. The as-prepared photocatalyst BAI-5 may have promising application prospects in environment purification.