(2023) Chemical Engineering Journal_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

Khiem T.C.; Huy N.N.; Kwon E.; Wacławek S.; Ebrahimi A.; Oh W.-D.; Ghotekar S.; Tsang Y.F.; Chen W.-H.; Lin K.-Y.A.

(Elsevier B.V.) Chemical Engineering Journal ISSN: 13858947 Vol.476 Issue. Article No.146404 DOI: 10.1016/j.cej.2023.146404

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[rad]− 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 S[sbnd]O 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. © 2023 Elsevier B.V.