Nanoarchitectonics of porous N-doped Co@CoS₂ with sulfur vacancies for enhanced peroxymonosulfate activation: Mechanisms and applications in oxytetracycline degradation

The strategy of constructing porous nitrogen-doped structures and abundant sulfur vacancies on the surfaces of transition metal-based catalysts has demonstrated immense potential for applications in fields of environmental remediation. However, the catalytic synergistic mechanisms of porous nitrogen doping and abundant sulfur vacancies at the catalyst surface are still subjects for further investigation, and the detailed relationship between sulfur vacancy defect structures and non-radical regulation remains unclear. In this study, Co-glycerate was utilized as a precursor to successfully synthesize porous nitrogen-doped Co@CoS₂ with abundant sulfur vacancies (S_v-N-Co@CoS₂) through straightforward nitrogen doping and sulfur vacancy introduction, thereby exploring the potential mechanisms for constructing efficient and low-cost peroxymonosulfate (PMS) catalysts. Benefitting from the unique electronic properties of porous nitrogen doping and the exposure of active surfaces due to abundant sulfur vacancies, the S_v-N-Co@CoS₂/PMS system achieved an impressive 95.6 % degradation efficiency of oxytetracycline (OTC) within 10 min. Notably, the introduction of sulfur vacancies facilitated the transition of active species generation to a predominantly singlet oxygen (¹O₂) non-radical pathway, thereby enhancing the stability of S_v-N-Co@CoS₂ in complex aqueous matrices and its effectiveness in OTC wastewater treatment. Furthermore, LC-MS techniques and DFT calculations were utilized to investigate the degradation pathways of OTC. This work provides new insights into the development of heterogeneous catalysts that integrate porous nitrogen doping and abundant sulfur vacancies, while also offering fresh perspectives on how surface engineering and defect engineering can modulate the active species in PMS catalysis to achieve efficient degradation of antibiotic-contaminated wastewater.