Efficient generation of singlet oxygen on Fe2O3/MoO3 Z-type heterojunction for removal of ciprofloxacin from water via photo-electro-Fenton-like system

Singlet oxygen (O-1(2)), a typical reactive oxygen species (ROS) with selective oxidation properties, holds great application prospects in water environment treatment. However, the O-1(2) generation mechanism in photo-electro-Fenton-like (PEF-like) system for water purification is still unclear. In this study, we developed a Fe2O3/MoO3 (abbreviated as FMO-x) Z-type heterojunction and achieved efficient degradation of ciprofloxacin (CIP). In-situ irradiated XPS, EPR, and DFT calculations confirmed that the coupling interface of FMO-1 Z-type heterojunction effectively enhanced the charge separation and transfer process, thus generating various ROS (O-1(2), center dot O-2(-), center dot OH and H2O2). In the FMO-1-PEF-like system, H2O2 was generated in-situ through 2e(-) ORR. In addition, ROS quantitative experiments showed that the yield of O-1(2), center dot O-2(-) and center dot OH was 29.76, 92.54 and 1.09 mu mol center dot L-1 in 60 min, respectively. EPR and XPS results indicated two potential routes for the O-1(2) generation: the reaction between center dot O-2(-) and Fe3+ and between center dot O-2 and H2O2. In the FMO-1-PEF-like system, the removal rate of CIP was 97.10 % in 60 min, and the kinetic constant was 0.0626 min(-1), which was 1.32 and 1.55 times higher than that of Fe2O3 and MoO3. This work developed a method using Fe2O3/MoO3 Z-type heterojunction to understand the mechanism of the O-1(2) generation in the PEF-like system.