Double Z-Scheme G-C3n4/bioi/cds Heterojunction with I3−/I− Pairs for Enhanced Visible Light Photocatalytic Performance

The g-C 3 N 4 /BiOI/CdS double Z-scheme heterojunction photocatalyst with I 3 - /I - redox pairs is prepared using simple calcination, solvothermal, and solution chemical deposition methods. The photocatalyst comprised mesoporous, thin g-C 3 N 4 nanosheets loaded on flower-like microspheres of BiOI with CdS quantum dots. The g-C 3 N 4 /BiOI/CdS double Z-scheme heterojunction has abundant active sites and in situ redox I 3 - /I - mediators and shows quantum size effects, which are all conducive to enhancing the separation of photoinduced charges and increasing the photocatalytic degradation efficiency for bisphenol A, a model pollutant. Specifically, the heterojunction photocatalyst achieves a photocatalytic degradation efficiency for bisphenol A of 98.62% in 120 min and photocatalytic hydrogen production of 863.44 μmol h -1 g -1 on exposure to visible light. The excellent visible-light photocatalytic performance is as a result of the Z-scheme heterojunction, which extends absorption to the visible light region, as well as the I 3 - /I - pairs, which accelerate photoinduced charge carrier transfer and separation, thus dramatically boosting the photocatalytic performance. In addition, the key role of the charge transfer across the indirect Z-scheme heterojunction has been elucidated and the transfer mechanism is confirmed based on the detection of intermediate I 3 - ions. Thus, this study provides guidelines for the design of indirect Z-scheme heterojunction photocatalysts.