Design and construction of a novel immobilized Z-scheme-Type II-heterojunction ZnO/ZnCo2O4-Co3O4|Co photocatalyst composite film for efficient norfloxacin degradation with simultaneous hydrogen evolution

The Z-scheme-Type II-heterojunction ZnO/ZnCo2O4-Co3O4 photocatalyst composite film (PCF) was prepared on the cobalt foil by using spin-coating and incomplete solid-state chemical reaction method, which solves the problems that the powder photocatalyst is difficult to recover and reuse and realizes the separation of CO2 and H2. In PCF, ZnO and ZnCo2O4 form a Z-scheme photocatalytic system and ZnCo2O4 and Co3O4 constitute a Type II-heterojunction photocatalytic system. The used cobalt foil acts as both a carrier of photocatalyst and a cathode. The structures and properties of PCF were studied by XRD, SEM, TEM, EDX, XPS, PL, TPR and EIS. Through photocatalytic norfloxacin degradation and hydrogen evolution, the effects of cobalt foil thickness, the coating Zn(OH)2 precipitation layer number, calcination temperature and calcination time on the photocatalytic performance of the Z-scheme-Type II-heterojunction ZnO/ZnCo2O4-Co3O4|Co PCFs were investigated. When the cobalt foil thickness is 0.10 mm, coating Zn(OH)2 precipitation layer number is 2, composite film is calcined under 500 degrees C for 3.0 h and norfloxacin concentration is 10 mg/L and 50 mg/L, norfloxacin degradation ratio and H2 evolution amount reach 80.70 % and 357.12 mu mol/dm2, respectively. In addition, a possible mechanism of norfloxacin degradation with simultaneous H2 evolution caused by immobilized Z-scheme-Type II-heterojunction ZnO/ZnCo2O4-Co3O4|Co PCF was proposed. It is hoped that the work has certain guiding significance to design an immobilized PCF for organic pollutants degradation with synchronous large-scale hydrogen evolution.