Improving the Performance of ZnS Photocatalyst in Degrading Organic Pollutants by Constructing Composites with Ag₂O

ZnS is a promising photocatalyst in water purification, whereas its low photon efficiency and poor visible-light response restrict its application. Constructing composites may help solve these problems. In this work, Ag₂O was introduced to ZnS for the first time based on their energy band characteristics to form a novel ZnS/Ag₂O composite photocatalyst. In the model reaction of degrading methylene blue, the as-designed catalyst exhibited high catalytic activity among a series of ZnS-based composite photocatalysts under similar conditions. The catalytic rate constant was up to 0.138 min^-1, which is 27.4- and 15.6-times higher than those of ZnS and Ag₂O. This composite degraded 92.4% methylene blue in 50 min, while the ratios were 31.9% and 68.8% for ZnS and Ag₂O. Catalytic mechanism study based on photoluminescence and radical-scavenging experiments revealed that the enhanced photocatalytic activity was attributed to the composite structure of ZnS/Ag₂O. The structure not only facilitated the separation and transmission of photogenerated carriers but also extended the light response range of the catalyst. The as-designed ZnS/Ag₂O composite is promising in degrading organic pollutants in water.