Z-Scheme Heterojunction α-Fe2O3/Tubular g-C3N4 with C Defects for Photocatalytic Degradation of Microcystin-LR in Water: Generation and Effect of Critical Species 1O2

Microcystin-LR (MC-LR) is susceptible to degradation by singlet oxygen (1O2) attack due to multiple unsaturated olefinic bond sites. In this study, the Z-scheme heterojunction α-Fe2O3/tubular g-C3N4 with C defects (α-Fe2O3/TDCN) was synthesized via hydrothermal and cocalcination methods. The efficient generation of 1O2 was realized by enhancing the photogenerated carrier separation and oxygen adsorption capabilities and was used to investigate the degradation process and mechanism of MC-LR. The results show that the degradation rate of MC-LR can reach nearly 100% within 60 min under visible light irradiation, and α-Fe2O3/TDCN possesses good stability and environmental friendliness. The relationship between photocatalyst performance and 1O2 generation was analyzed by density functional theory (DFT) calculations. Based on probe experiments, LC–MS data, and DFT calculations, the mineralization process of MC-LR dominated by 1O2 was analyzed. This study provides a reference for addressing MC-LR pollution in eutrophic aquatic environments and the direction of specific control of MC-LR mineralization.