Carbon encapsulated Fe0/Fe oxides for heterogeneous electro-Fenton process: Promoting Fe(II) regeneration under nanoconfinement☆

The nanoconfinement effect of the carbon shell enables the Fe-based catalyst to stably catalyze the electro-Fenton (EF) reaction under harsh operating conditions, but the Fe(II) regeneration efficiency in a confined environment remains unsatisfied. In this study, Fe0 was, for the first time, incorporated to the carbon encapsulated iron-based catalyst to accelerate the Fe(II) regeneration under nanoconfinement in the EF process. The carbon shell encapsulated Fe0/FeO (Fe0/FeO@C) was constructed by pyrolyzing Fe-containing chitosan gels on carbon felt, achieving 13 times faster ciprofloxacin (CIP) degradation than catalysts only containing iron oxide. Structural characterizations confirmed that Fe0 and FeO were uniformly encapsulated within the carbon shell, which shows better Fe(III)/Fe(II) redox efficiency than that of carbon coated iron oxide. Density functional theory (DFT) calculations show that when the carbon shell couples with Fe0, the electron of Fe0 can delocalize to the carbon shell to forming a stable electron-rich interface that promotes Fe(II) regeneration under nanoconfinement. This study proposes an economical and environmentally friendly approach to enhance Fe(II) regeneration under nanoconfinement, providing new insights for the rational design of heterogeneous electro-Fenton catalysts.