Construction of mesoporous S-doped Co3O4 with abundant oxygen vacancies as an efficient activator of PMS for organic dye degradation

Abstract

The slow kinetics of the Co³⁺/Co²⁺ catalytic redox cycle on the surface of Co-based solid catalysts greatly limits their application in sulfate radical-based advanced oxidation processes. To overcome this challenge, nanoparticle-assembled rod-like S-doped Co₃O₄ (S-Co₃O₄) with abundant oxygen vacancies (OVs) and a mesoporous structure was prepared to activate peroxymonosulfate to degrade various organic dye contaminants. The abundant OVs and good charge transfer capability of S-Co₃O₄ accelerated the Co³⁺/Co²⁺ redox cycle due to the incorporation of S atoms, which improved the Co²⁺ recovery. The S-Co₃O₄ catalysts exhibited excellent catalytic activities, and the methylene blue (MB) degradation rate reached 100% within 6 min. The degradation rate constant of the catalytic reaction for the S-Co₃O₄ + PMS system (0.78 min⁻¹) was 30 times higher than that of the Co₃O₄ + PMS system (0.026 min⁻¹), which may be due to the synergy between the high Co²⁺ content, abundant OVs, and large surface area. After six consecutive cycles, the MB degradation efficiency still reached 94.5%, and the cobalt leaching of S-Co₃O₄ was only 0.42 mg L⁻¹. In the S-Co₃O₄-activated PMS system, SO₄˙⁻ and ¹O₂ were the main active species, but ¹O₂ played the main role in contaminant degradation. This study provides a novel method for accelerating Co³⁺/Co²⁺ circulation and reducing Co ion leaching from the surface of heterogeneous Co-based catalysts to substantially enhance their performance.