Hollow porous structure engineering for enhanced Fe site utilization and H2O2 activation in electro-Fenton degradation

Heterogeneous electro-Fenton technology holds great promise for organic wastewater treatment, yet its efficiency is often constrained by the inefficient conversion of H 2 O 2 to hydroxyl radicals (·OH), primarily due to the poor accessibility of active sites. To address this challenge, we designed an iron-loaded hollow porous carbon sphere catalyst (Fe-HCS). This unique architecture features a uniform hollow spherical morphology, a high specific surface area (1065.2 m 2 g −1 ), abundant mesopores, and a large pore volume (1.56 cm 3 g −1 ). The hollow structure effectively suppresses Fe aggregation during carbonization, resulting in highly dispersed Fe sites. Electrochemical analyses reveal that Fe-HCS possesses significantly enhanced H 2 O 2 activation capability. Its double-layer capacitance is approximately 90% higher than that of a non-hollow iron‑carbon catalyst (Fe C), indicating a larger electrochemically active surface area and greater exposure of active sites. At −0.6 V vs. SCE, the Fe-HCS system achieves 97% phenol removal within 60 min, with a pseudo-first-order rate constant of 2.68 h −1 , which is 3.25 times that of Fe C. These results demonstrate that constructing a hollow porous architecture is an effective strategy to improve active site utilization and H 2 O 2 activation in heterogeneous electro-Fenton systems.