Construction of ZnO/CdS Z-Scheme Heterojunction and Enhanced Photocatalytic Performance

Semiconductor photocatalysts have been widely used to remove pollutants from industrial wastewater. Organic pollutants and heavy metal ions often coexist in polluted environments. However, the studies on water pollution have only focused on the treatment of single organic pollutants or heavy metal ions. Herein, a ZnO/CdS composite is synthesized using a simple hydrothermal method. The hybrid shows excellent photocatalytic performance for the simultaneous removal of rhodamine B (RhB) dye and hexavalent chromium (Cr(VI)) complex contaminants under visible-light irradiation. Photocatalytic efficiencies of 98.93% for RhB degradation and 94.59% for Cr(VI) reduction are achieved after 120 min of irradiation. The ZnO/CdS composite exhibits superior photocatalytic activity compared with pristine ZnO and CdS. The Z-scheme heterojunction formed between ZnO and CdS promotes the separation and transfer of photogenerated carriers, thus enhancing the photocatalytic performance of the composite. Reusability and stability investigations demonstrate >90% RhB degradation and Cr(VI) reduction after the 3rd cycle, suggesting the chemical stability of the ZnO/CdS composite with the potential for practical applications. According to the radical trapping experiment, RhB is decomposed by the co-oxidation of h(+) and center dot O-2(-). Meanwhile, the Cr(VI) in K2Cr2O7 is reduced to Cr(III) by e(-).