A novel double S-scheme photocatalyst Bi7O9I3/Cd0.5Zn0.5S QDs/WO3−x with efficient full-spectrum-induced phenol photodegradation

In this work, Bi7O9I3/Cd0.5Zn0.5S QDs/WO3−x ternary heterojunction with full spectrum response was prepared and applied in the photodegradation of phenol. The results of photocatalytic experiments showed that the prepared Bi7O9I3/Cd0.5Zn0.5S QDs/WO3−x heterojunction had the highest performance under full spectrum, visible and near-infrared light irradiation, and the reaction rates were 4.02, 3.75 and 5.71 times that of pure Bi7O9I3, respectively. This performance improvement results from the construction of double S-scheme heterojunction and the full-spectrum response, which had effective charge distribution and migration as well as an excellent response to sunlight. In addition,·OH and·O2- took the lead role in the process of photodegradation. Combined with the free radical-trapping experiment, ESR experiment and DFT theoretical calculation, the photocatalytic mechanism of double S-scheme system was proposed. This work is contributory to designing novel photocatalytic materials with dual S-scheme heterojunction and the efficient purification of wastewater in environmental remediation. [Display omitted] •Bi7O9I3/Cd0.5Zn0.5S QDs/WO3−x ternary heterojunction with full spectrum response was prepared.•The degradation efficiency of BCW-2 heterojunction to phenol reached 100% under full-spectrum irradiation within 90 min.•·OH and·O2- took the lead role in the process of photodegradation.