Highly efficient electro-Fenton process on hollow porous carbon spheres enabled by enhanced H2O2 production and Fe2+ regeneration.

Electro-Fenton (e-Fenton) is a promising method for wastewater treatment that relies on powerful ·OH generated via the decomposition of electro-generated H2O2 catalyzed by Fe2+. In this regard, developing a catalyst capable of simultaneously producing H2O2 and accelerating Fe2+ regeneration is of considerable importance; however, this remains a challenge because of the difficulty in modulating the electronic microenvironment. Herein, a hollow porous carbon sphere catalyst (HPCS) is developed to synchronously enhance H2O2 generation and accelerate Fe3+/Fe2+ cycling by constructing an electron-rich microenvironment via surface curvature regulation. The Fe2+ regeneration efficiency reaches 35.5% on HPCS featuring a larger curvature structure (HPCS-TPOS), which is 1.6 times higher than the smaller curvature HPCS-S catalyst (22.8%). Density functional theory reveals that the electron-rich microenvironment on the outer surface of high curvature structure promotes Fe2+ regeneration. The H2O2 production rate on HPCS-TPOS is 47.2 mmol L-1 h-1, exceeding the state-of-the-art e-Fenton catalysts reported. Benefiting from the concurrent high-efficiency of H2O2 production and Fe2+ regeneration, HPCS-TPOS e-Fenton is demonstrated to be efficient for sulfamethoxazole removal with the kinetic rate of 0.30-0.72 min-1 at pH 3-7. This work offers new insight into the design of efficient catalysts by rationally regulating curvature structures for wastewater treatment.