SO₄^•− and •OH radicals are important oxidative species that play important roles in the oxidation of organic contaminants by peroxomonosulfate (PMS)/persulfate (PS) and Co₃O₄ under acidic conditions. However, the facet effect of Co₃O₄ on the catalytic oxidation of phenol by PS under alkaline conditions has not been investigated yet. In this study, we synthesized three Co₃O₄ nanoparticles with different facets [rod (110), cube (100) and octahedra (111)]. The Co₃O₄ rods show the highest catalytic reactivity in the oxidation of phenol by PS, followed by Co₃O₄ cubes and Co₃O₄ octahedra. Quenching experiments and EPR analysis rule out contributions of SO₄^•−, •OH, O₂^•− and ¹O₂ to phenol oxidation and suggest that H-abstraction from phenol to phenoxyl radicals is an important pathway in all Co₃O₄-PS systems. The analysis of total organic carbon (TOC) and solid characterizations reveal that more than 96.6% phenol has been transformed into polyphenols, instead of being mineralized into smaller organic molecules or CO₂ in the rod-PS-phenol system. The DFT (density functional theory) calculations further confirm that PS is more readily activated via a non-radical pathway on the Co₃O₄(110) plane with appropriate Co(II)-Co(II) distances, and the activated O-O bonds then abstracts H atoms from phenol molecules with the production of phenoxyl radicals, as well as SO₄^•- and •OH radicals. The produced phenoxyl radicals then link together to form dimer, trimer, oligomer and eventually insoluble polymers. This study not only enriches our understanding on the facet effect of different Co₃O₄ in the oxidation of phenol, but also gives new insight into turning phenolic wastes into polyphenol treasures.

SO ₄ ^{• -}和•OH自由基是重要的氧化性物质，在酸性条件下，过氧单硫酸盐（PMS）/过硫酸盐（PS）和Co ₃ O ₄在有机污染物的氧化中起重要作用。然而，尚未研究Co ₃ O ₄对碱性条件下PS催化苯酚催化氧化苯酚的作用。在这项研究中，我们合成了三个具有不同刻面的Co ₃ O ₄纳米粒子[杆（110），立方体（100）和八面体（111）]。Co ₃ O ₄棒在PS氧化苯酚中表现出最高的催化反应活性，其次是Co ₃ O₄个立方体和Co ₃ O ₄八面体。淬火实验和EPR分析排除SO的贡献₄ ^{• -}，•OH，O- ₂ ^{• -}和¹ Ø ₂至酚氧化，并建议由苯酚H-抽象，苯氧基是所有合作的重要途径₃ Ø ₄ - PS系统。对总有机碳（TOC）和固体特征的分析表明，超过96.6％的苯酚已转化为多酚，而不是矿化成较小的有机分子或CO ₂在棒-PS-苯酚体系中。DFT（密度泛函理论）计算进一步证实，PS通过在Co ₃ O ₄（110）平面上具有适当的Co（II）-Co（II）距离和活化的OO键的非自由基途径更容易活化然后从苯酚分子中提取H原子，并生成苯氧基自由基以及SO ₄ ^•-和•OH自由基。然后产生的苯氧基自由基连接在一起形成二聚体，三聚体，低聚物和最终不溶的聚合物。这项研究不仅丰富了我们对不同Co ₃ O ₄在苯酚氧化中的刻面效果的理解，而且对将酚类废物转化为多酚宝藏提供了新的见解。