Promoted generation of singlet oxygen by oxygen vacancies-enriched Co3O4/g-C3N4 catalyst for efficient degradation of phenanthrene

Efficient, stable, and reusable composite of Co3O4/g-C3N4 with abundant oxygen vacancies (OVs) were suc-cessfully constructed using a facile grinding and calcination method. The catalytic performances of OVs-enriched Co3O4/g-C3N4 activated peroxymonosulfate (PMS) for the degradation of phenanthrene (PHE) and their un-derlying mechanisms were investigated. The catalytic activity of xCo3O4-C3N4 with OVs was significantly greater than that of Co3O4-C3N4 without OVs, and there was a substantial positive correlation between the degradation rate constant of PHE and the OVs content in xCo3O4-C3N4. Quenching experiments and EPR tests demonstrated that 1O2 is the dominant active species in the 2.0Co3O4-C3N4/PMS system, which differs from the radical -dominated activation pathway of conventional cobalt-based heterogeneous catalysts. The results indicate that the OVs introduction in the catalyst can effectively modulate the PMS activation pathway, and the proposed non -radical systems can achieve efficient degradation of PHE. In addition, the synergistic interaction between the redox cycle of Co2+/Co3+ and the electron-rich O-C3N4 carrier favored the degradation of PHE via the radical pathway. This study provides a new theoretical basis and reference for the facile preparation of PMS catalysts and even envision this approach may open new vistas in the application of non-radical systems in refractory organic pollutant treatment.