Facile synthesis of Z-scheme ZnO/Ag/Ag3PO4 composite photocatalysts with enhanced performance for the degradation of ciprofloxacin

Single-component silver phosphate (Ag3PO4) is faced with problems of rapid recombination and poor stability of photo-generated carriers, which severely limits its degradation and practical application of organic pollutants under visible light. In this present paper, we prepared a new type of ZnO/Ag/Ag3PO4 composite photocatalyst with simple precipitation deposition method and photoreduction technology. The structure, crystal form, morphology and light absorption were characterized by XRD, XPS, BET, SEM, TEM, EDS, UV–vis DRS, PL, EIS and transient photocurrent responses. Ciprofloxacin (CIP) was used as the target pollutant to test its photocatalytic activity and stability. The results reveals that the photocatalytic activity of ZnO/Ag/Ag3PO4 composite is significantly enhanced compared with single-component and binary catalysts. After 120 min of visible light irradiation, the degradation of CIP reached 87.1%, and after four cycles, the degradation rate still occupied 75%. The enhanced photocatalytic activity lies in the synergistic effect of ZnO, Ag3PO4 and Ag and the plasmon resonance effect (SPR) on the surface of nano-Ag, which increases the specific surface area of the material, broadens the absorption of visible light, and improves the efficiency of electron-hole pair separation. The capture experiment gives information that the primary active substance is superoxide radical (•O2−), and we proposed a possible Z-scheme photocatalytic mechanism.