Chlorine-Doped Co3O4 Accelerates Interfacial Charge Transfer for Efficient Peroxymonosulfate Activation: Radical-Dominated Bisphenol A Degradation

Cobalt oxide (Co3O4), a transition metal oxide with a cubic spinel structure, shows high potential in peroxymonosulfate (PMS) activation, while its catalytic efficiency is often limited by sluggish interfacial charge transfer. In this study, a chlorine-doped Co3O4 (Cl-Co3O4) was synthesized via a hydrothermal method for the degradation of bisphenol A (BPA) through PMS activation. Systematic characterizations and electrochemical tests demonstrated that chlorine doping could effectively modulate the surface electronic structure of the catalyst, significantly reducing the interfacial charge transfer resistance. Degradation performance evaluations revealed that, compared to pristine Co3O4, Cl-Co3O4 exhibited a significantly enhanced BPA degradation, achieving near-complete removal of BPA within 15 min under neutral to weakly alkaline conditions. The optimal operational parameters were determined as catalyst dosage of 0.20 g/L, PMS concentration of 0.10 mM and initial pH of 7.0–9.0, with the pseudo-first-order rate constant reaching 0.37 min−1. High-concentration NO3− showed weak inhibition, while Cl− showed moderate inhibition; 50 mM HCO3− drastically reduced the rate constant to 0.05 min−1 and almost completely suppressed the reaction. Sulfate (SO4•−) and superoxide (O2•−) radicals were the primary reactive species in this system, explicitly excluding the role of the non-radical electron transfer pathway. Furthermore, three plausible BPA degradation pathways involving C-C bond cleavage, hydroxylation and C-O bond breakage were proposed with 19 intermediates identified. Ecotoxicological assessments based on ECOSAR verified that both acute and chronic toxicity of the intermediates to fish, daphnid and green algae decreased gradually, and the final small-molecule products exhibited significantly lower toxicity than the parent BPA. This study provides a novel strategy for enhancing the PMS activation performance of cobalt-based catalysts by modulating their electronic structures via halogen doping.