Synthesis of H₂O₂ to Self-Catalyzed Generation of ^•OH over ZnO/CuI/Cu Foam Electrode for the Self-Fenton Cleaning of Wastewater

A novel ZnO/CuI/Cu foam electrode was constructed, which demonstrated excellent photoelectrocatalytic activity for the self-Fenton degradation of tetracycline in water. The H₂O₂ yield was 405.0 μmol L^-1 over ZnO/CuI/Cu foam (CIZ-3) under light irradiation (100 mW cm^-2) for 5 h at -1.23 V (vs NHE), which was 1.7 times higher than that of ZnO/Cu foam and 1.6 times higher than that of CuI/Cu foam, respectively. The 99.0% of tetracycline was degraded by CIZ-3 due to its efficient yield of H₂O₂ to self-catalyzed generation of ^•OH. The results of the open-circuit potential between CuI and ZnO displayed that the electrons from the conduction band of CuI flowed to ZnO and the holes from the valence band of ZnO migrated to CuI. As a result, the photogenerated electron-hole pairs of ZnO/CuI were efficiently separated, which greatly promoted the photoelectrocatalytic activity of ZnO/CuI/foam. The toxicity of the aqueous tetracycline solution was significantly reduced by observing the growth of Escherichia coli in the treated wastewater.