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.

[Display omitted] • Co 3 O 4-x -0.20 with the yolk-shell structure is constructed via tailoring oxygen vacancy (OV) • OV reduces charge transfer resistance and increases the conductivity for enhancing catalytic activities. • Phenol degradation is accelerated by single-electron transfer and Co(IV) = O generation. • Single-electron transfer of phenol is induced by electron-deficient OV due to electron donation to O 2. • Relationship between Co(IV) = O and OV is unraveled by elongated S-O and shortened Co O bonds. As Co 3 O 4 represents a promising material for peroxymonosulfate (PMS) activation, a yolk-shell-structured nanosphere, Co 3 O 4-x -0.20, is developed here for maximizing its catalytic activity by governing electronic structures via tailoring oxygen vacancies (OV) of Co 3 O 4. This OV-tailored Co 3 O 4 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 O 2 to form O 2 − followed by O 2 evolution after 1O 2 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 S O bond in the Co(II)-O-SO 3 -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 Co 3 O 4-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. [ABSTRACT FROM AUTHOR]