Improving peroxymonosulfate activation via surface-constructed oxygen vacancies on Co0.2FeOx for durable water decontamination

Activating peroxymonosulfate (PMS) to generate sulfate radicals (SO₄^·-) is an effective method for water purification. An efficient, low-cost, and easily synthesized catalyst ensures decontamination performance and practical application feasibility. In this work, oxygen vacancy-enriched magnetic Co_0.2FeO_x was synthesized by isomorphous substitution of Fe³⁺ with Co²⁺ in α-FeOOH and employed to activate PMS to degrade iohexol, an iodinated X-ray contrast media widely detected in water. Co_0.2FeO_x exhibited higher performance than previously reported transition metal oxides. Iohexol could be effectively degraded in the Co_0.2FeO_x-catalyzed system from pH 3.5 to 10.5 compared to PMS oxidation alone. In situ tests in D₂O and H₂O using ATR-FTIR spectra inferred that the oxygen vacancies on the Co_0.2FeO_x surface could facilitate the formation of surface hydroxyl groups, which could complex HSO₅^- to form Me-(OH)-OSO₃^-. Electron transfer in the inner complex via the redox of Co(II)/Co(III) and Fe(III)/Fe(II) caused the breakage of the O-O bonds, thus promoting free radical generation. ESR spectra identified SO₄^·- and ·OH as the predominant active species. This study suggests new ideas for the synthesis of efficient catalysts and elucidates new insights into the interfacial mechanism of PMS activation