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.
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