Novel Fenton-like system based on bifunctional MgO/g-C3N4 S-scheme heterojunction photoanode for efficient tetracycline degradation

A novel photoelectrocatalytic (PEC) system consisting of S-scheme MgO/g-C3N4 photoanode and modified carbon felt (MCF) cathode was designed for efficient degradation of tetracycline, in which photoanode had both efficient photocatalytic performance and activation of H2O2 produced by the MCF cathode. After 30min of LED irradiation, the PEC system could completely remove tetracycline at cathodic bias of -0.5V (vs. Ag/AgCl), and the degradation rate constants were 5.3 and 1.5 times that of electrocatalysis and photocatalysis. The charge transfer mechanism of S-scheme MgO/g-C3N4 was verified by experimental studies and DFT calculations. Mg-N coordination was the key to activate H2O2 to produce singlet oxygen (1O2) and hydroxyl radicals (•OH). The PEC system had excellent degradation performance at pH ranges 4-10, which solved the bottleneck that Fenton system is effective at narrow pH range. This study provides new ideas for preparation of bifunctional photoanodes and new insights into the PEC process.