Tailoring oxygen vacancies in Co3O4 yolk-shell nanospheres via for boosted peroxymonosulfate activation: Single-electron transfer and high-valent Co-oxo species-dominated non-radical pathways

As Co3O4 represents a promising material for peroxymonosulfate (PMS) activation, a yolk-shell-structured nanosphere, Co3O4-x-0.20, is developed here for maximizing its catalytic activity by governing electronic structures via tailoring oxygen vacancies (OV) of Co3O4. This OV-tailored Co3O4 enables single-electron transfer and generates high-valent cobalt-oxo species (Co(IV) = O) to achieve the fastest phenol degradation. The single-electron transfer is unraveled by an electron donation of Co atoms near OV to O2 to form O2− followed by O2 evolution after 1O2 and the charge balance maintained by an electron acquisition from phenol by the electron-deficient Co atoms. Meanwhile, the generation of Co(IV) = O by the cleavage of the SO bond in the Co(II)-O-SO3-OH complex accepts electrons from phenol to turn back to Co(II) and Co(III), causing phenol oxidation. These results demonstrate the pre-eminence of Co3O4-x-0.20 over the reported catalysts for phenol degradation and also offer insights into the mechanism of OV triggering electron donation and enhancing Co(IV) = O generation.