Molecular-Level Tuning of Active Sites of the Carbonaceous Catalyst for Boosting Electrochemical H₂O₂ Production and its Application in Electro-Fenton-like Degradation of Organics

Constructing effective cathode materials for simultaneously producing and activating H₂O₂ to achieve functional reduction of O₂ for ^•OH production is crucial for the development of a heterogeneous electro-Fenton process in wastewater treatment. In this study, the active groups of the carbonaceous catalyst for electrochemical O₂ reduction have been tuned and identified from the molecular level. Proton amines and pyrolysis temperature present significant influences on the polymerization process of the phenolic-formaldehyde resin, thereby altering the structure, functional groups, defects, and activity of the carbonized phenolic-formaldehyde catalyst. A graphite felt-based gas-diffusion electrode composed of the active carbonaceous catalyst, organic binder, and transition metal species has been employed in the electron-Fenton-like system to achieve highly selective H₂O₂ and ^•OH production for water decontamination. The optimized gas-diffusion electrode exhibits a high H₂O₂ selectivity of 87.6-92.4% at 0.2-0.4 V vs standard hydrogen electrode (SHE), a higher current efficiency of 99.1%, and a H₂O₂ production rate of 6.29 mg cm^-2 h^-1 at 10 mA cm^-2, respectively. Furthermore, owing to the efficient decomposition of H₂O₂ into ^•OH by Mnⁿ⁺ species, humic acid can be efficiently degraded in an electron-Fenton-like process. The electrochemical oxidation performance and energy consumption efficiency for the treatment of real landfill leachate have been evaluated. The results demonstrate that the relational design and fabrication of a high-performance gas-diffusion electrode based on regulating the active carbonaceous O₂ reduction catalyst and H₂O₂ activation catalyst have huge potential for electrochemical wastewater treatment.