Generating ¹O₂ and Co^IV=O through efficient peroxymonosulfate activation by ZnCo₂O₄ nanosheets for pollutant control

Heterogeneous advanced oxidation processes (AOPs) based on non-radical reactive species are considered as a powerful technology for wastewater purification due to their long half-lives and high adaptation in a wide pH range. Herein, we fabricate surface Co defect-rich spinel ZnCo₂O₄ porous nanosheets, which can generate ≡Co^IV=O and ¹O₂ over a wide pH range of 3.81–10.96 by the formation of amphoteric ≡Zn(OH)₂ in peroxymonosulfate (PMS) activation process. Density functional theory (DFT) calculations show Co defect-rich ZnCo₂O₄ possesses much stronger adsorption ability and more electron transfer to PMS. Moreover, the adsorption mode changes from terminal oxygen Co–O–Co to Co–O, accelerating the polarization of adjacent oxygen, which is beneficial to the generation of ≡Co^IV=O and ¹O₂. Co defect-rich ZnCo₂O₄ porous nanosheets exhibit highly active PMS activation activity and stability in p-nitrophenol (PNP) degradation, whose toxicity of degradation intermediates is significant reduction. The Co defect-rich ZnCo₂O₄ nanosheet catalyst sponge/PMS system achieved stable and efficient removal of PNP with a removal efficiency higher than 93% over 10 h. This work highlights the development of functional catalyst and provides an atomic-level understanding into non-radical PMS activation process in wastewater treatment.