Enhanced mechanism of a TiO2/g-C3N4 photoanode in photoelectrocatalytic synergistic persulfate activation for antibiotic degradation

Abstract

Photocatalysis and persulfate-based advanced oxidation technologies have received considerable attention. In this study, a Z-scheme heterojunction photoanode composed of graphitic carbon nitride and titanium dioxide (TiO₂/g-C₃N₄) was constructed to develop an efficient photoelectrochemical–persulfate (PEC/PMS) activation system for antibiotic degradation. The PEC/PMS system significantly accelerated electron transfer and enhanced the photoresponse current, achieving 96.04% tetracycline removal within 12 min. The optimal operating conditions were a bias voltage of 1.0 V, a PMS concentration of 0.2 mmol L⁻¹, and a neutral to slightly alkaline environment. The system effectively resisted interference from water matrix components and achieved over 88% removal of multiple antibiotics in aquaculture pond water. TiO₂/g-C₃N₄ exhibited a Z-scheme heterostructure, and its photocatalytic activity served as the primary driving force in the synergistic process, in which degradation was dominated by radical pathways (˙OH and ˙SO₄⁻) accompanied by a non-radical ¹O₂ pathway. The calculated synergy factor further confirmed that the introduction of an external electric field and PMS markedly enhanced electron transfer and produced a pronounced synergistic effect.