Mesoporous sulfur-modified metal oxide cathodes for efficient electro-Fenton systems

Abstract

Development of cathode materials with high activity, stability, and wide operating pH range is crucial for electro-Fenton reactions. Herein, mesoporous sulfur-modified metal oxides were coated onto stainless steel meshes and applied as a cathode to promote in-situ generation of H2O2 for electro-Fenton processes. Different mesoporous metal oxides with and without sulfur-modification were synthesized using Fe, Ni, and Zn precursors to investigate the effect of sulfur doping. Among them, sulfur doped Fe2O3 showed the best electrocatalytic performance, and it was attributed to several factors such as large specific surface area, high-efficiency oxygen reduction reaction activity, and enhanced electron/charge transfer. The effect of operational parameters such as applied voltage, catalyst dosage, initial pH, initial concentration of phenol, and electrolyte concentration on the catalytic performance was investigated in terms of degradation efficiencies and rate constants. The results indicate that for high concentration 100 ppm phenol solution, 78% removal efficiency with a rate constant of 0.186 h−1 was achieved with sulfur-doped Fe2O3 on stainless steel mesh electrode under optimal conditions in 8 h. This cathode worked effectively in a wide pH range (3–10) due to its pH self-control ability and exhibited superior stability and reusability with insignificant deterioration in the catalytic activity. This study offers an alternative approach to fabricate electrocatalysts with low-cost sulfur-doped metal oxides for electro-Fenton systems.