Construction of Z-Scheme g-C3N4/RGO/WO3 with in situ photoreduced graphene oxide as electron mediator for efficient photocatalytic degradation of ciprofloxacin.

Z-scheme photocatalyst g-C3N4/RGO/WO3 with reduced graphene oxide (RGO) as the electron mediator was synthesized via a facile photoreduction method. According the results of photoluminescence (PL), electrochemical impedance spectroscopy (EIS) and photocurrent response, g-C3N4/RGO/WO3 presents more efficient separation of charges and enhanced electronic mobility than g-C3N4/WO3, g-C3N4 and WO3, which benefits from the excellent electron transfer property of RGO. Reactive species trapping experiments and electron paramagnetic resonance (EPR) test demonstrated that superoxide radical (O2-) and hydroxyl radical (OH) were produced because of the high redox capacities caused by the unique transfer behaviors of charges in Z-scheme photocatalyst g-C3N4/RGO/WO3. In the absence of RGO as electron mediator, only holes (h+) participates the degradation process of ciprofloxacin (CIP) due to the decreased redox capacities of g-C3N4/WO3 compared with g-C3N4/RGO/WO3. Therefore, the degradation rate of Ciprofloxacin (CIP) over g-C3N4/RGO/WO3 composite was nearly twice as much as that over g-C3N4/WO3. In addition, the analysis of intermediates provides insight into the degradation pathway of CIP.