Sulfur-doped MgFe2O4 with oxygen vacancies: Unveiling the synergistic role of electron transfer pathways in boosting radical generation for efficient peroxymonosulfate activation

Sulfur-doped MgFe 2 O 4 constructs oxygen-vacancy-rich surfaces, enhancing interfacial charge transfer. • Fe centers and the electron transfer pathway form a dual-electron activation mechanism for PMS activation. • The electron transfer pathway boosts radical generation by 2.0-fold compared to single-pathway systems. • S-MgFe 2 O 4 achieves 91.59% tetracycline degradation with 85.98% activity retention after six cycles. The electron transfer pathway (ETP) in Fenton-like reactions enables the selective degradation of electron-rich micropollutants, yet the potential synergistic interplay between ETP and radical pathways remains underexplored. Herein, we synthesize sulfur-doped MgFe 2 O 4 with abundant oxygen vacancies (S-MgFe 2 O 4 /OVs) and unveil a novel “dual-electron migration pathway,” where ETP synergistically enhances radical generation for peroxymonosulfate (PMS) activation. Electrons can migrate from electron-rich pollutants to Fe sites via an electron shuttling bridge (S-MgFe 2 O 4 ), serving as an additional electron source to accelerate the rate-limiting step of Fe(III)/Fe(II) cycling, thereby promoting PMS cleavage and amplifying the generation of SO 4 •− and • OH. This synergy enables the S-MgFe 2 O 4 /PMS system to achieve 91.59% tetracycline degradation within 20 min (k obs  = 0.1125 min −1 , 1.76-fold higher than that of undoped MgFe 2 O 4 ) with excellent stability (85.98% activity retention after six cycles). Our work pioneers a new paradigm for regulating radical generation via electron transfer, offering a transformative strategy for designing synergistic advanced oxidation process catalysts.