Oxygen reduction reaction electrocatalysis inducing Fenton-like processes with enhanced electrocatalytic performance based on mesoporous ZnO/CuO cathodes: Treatment of organic wastewater and catalytic principle

Abstract

To treat typical organic wastewater efficiently, a novel Fenton-like processes based on ZnO/CuO composite cathode induced by oxygen reduction reaction (ORR) electrocatalysis with enhanced electrocatalytic performance was established successfully. Electrochemical testing investigation indicated that the ZnO/CuO cathode possessed conspicuous redox peak and better conductivity than uncompounded electrodes. Additionally, the removal efficiency of methylene blue and its chemical oxygen demand (COD) reached 96.4% and 70.8% after 120 min, respectively. Next, the feasibility of the material in practical application was also discussed. Subsequently, electrocatalytic principle based on valence state changes of metal elements on the electrode surface were also studied by x-ray photoelectron spectroscopy (XPS). Redox reactions between the active species H2O2 and the species Cu+ promoting Fenton-like processes were deduced. Namely, the conversion of Cu(I) and Cu(II) on the electrode surface was accompanied by OH generation. The combination of ZnO and CuO improved the surface morphology, increasing the active site of ORR and the yield of H2O2, thus greatly enhanced the Fenton-like activity. Finally, the main intermediates were identified by Gas chromatography-mass spectrometer (GC-MS), and possible pathways for dye degradation were proposed. In short, the research of ZnO/CuO cathode provided great significance for heterogeneous Fenton-like degradation and also showed its application potential in water treatment and remediation.