A binder-free electrode for efficient H2O2 formation and Fe2+ regeneration and its application to an electro-Fenton process for removing organics in iron-laden acid wastewater

The electro-Fenton process, with its capacity for in-situ H2O2 formation and Fe2+ regeneration, is a striking alternative to the traditional chemical-Fenton process. However, the frequent requirement of extra binders for electrode fabrication leads to low catalyst utilization, a complex fabrication process, and weak conductivity. Herein, a three-dimensional (3D) porous electrode was fabricated in-situ on a Ni foam (NF) substrate integrated with nitrogen-doped carbon nanotubes ([email protected]) derived from carbonization of zeolitic imidazolate framework-8 (ZIF-8) without any binder. The resulting 900/[email protected] cathode (synthesized at 900 °C) was high in surface area, N content, and degree of graphitization, achieved high performance of H2O2 production (2.58 mg L−1 h−1 H2O2/mg catalyst) at -0.7 V (vs. SCE), and enabled prompt regeneration of Fe2+. The electro-Fenton system equipped with the 900/[email protected] cathode was effective in removing a diverse range of organic pollutants, including rhodamine B (RhB), phenol, bisphenol A (BPA), nitrobenzene (NB), and Cu-ethylenediaminetetraacetic acid (EDTA), and significantly attenuating the concentration of chemical oxygen demand (COD) in the real acid wastewater, exhibiting superior activity and stability. This binder-free and self-supporting electro-Fenton cathode was thus shown to be an attractive candidate for application to wastewater treatment, particularly those rich in organics, acids, and Fe3+/Fe2+.