CoFe-PBA-derived carbon-coated CoSe2 hollow nanocubes for peroxymonosulfate activation toward sulfamethoxazole degradation: Performance and mechanism

Hollow carbon-coated CoSe 2 cubes (CCS2) were derived from a CoFe-PBA template. • Tuning Se-vacancy density reshapes Co electronic state for PMS activation. • CCS2 removed 95% SMX in 10 min with an apparent rate constant of 1.39 min −1 . • 1 O 2 and SO 4 •− dominate, while ·OH, O 2 •− and Co(IV)=O play auxiliary roles. • CCS2/PMS retained high activity over pH 3–11 and in real water matrices. The growing variety and chemical intricacy of refractory organic species in aqueous environments has elevated the design of robust, sustainable, and eco-compatible peroxymonosulfate (PMS) activation platforms into a key research thrust within advanced oxidation. Targeting the recurring drawbacks of common heterogeneous catalysts (insufficient active-site exploitation, considerable metal dissolution, and weak cyclic stability), we built a carbon-shelled cobalt selenide system (CCS) starting from CoFe-PBA, by sequentially performing hydrothermal selenization, polydopamine wrapping, and inert-atmosphere annealing. Modulating the selenium vacancy (V Se ) population proved to substantially reinforce PMS activation. Among the synthesized series, CCS2 emerged as the top performer, eliminating 95% of 20 mg L −1 sulfamethoxazole (SMX) over 10 min. Multi-technique characterization coupled with mechanistic probing revealed that incorporating V Se rearranged the electron distribution around Co atoms, raised the proportion of Co 2+ , and tightened the anchoring of oxygen-containing surface species. Concurrently, under-coordinated Se centers played a role in maintaining the Co 3+ /Co 2+ redox cycle, which together drove PMS through several parallel activation channels. Spin-trapping EPR measurements, quenching experiments, and selective probe assays jointly confirmed coexistence of SO 4 •− , •OH, 1 O 2 , and high-valent Co-O species in the CCS2/PMS system, with 1 O 2 and SO 4 •− as the principal contributors driving SMX abatement. These results elucidate the way anion vacancies tailor the electronic landscape and synergistic catalytic pathways of transition-metal selenides under PMS activation, providing a new conceptual route for designing durable sulfate-radical-based AOP catalysts via defect engineering. Download: Download high-res image (262KB) Download: Download full-size image