Novel insights into Co synergy and electron-transfer pathways during the oxidation of contaminants by [tbnd]Cu-OOSO₃^- in CuCo₂O_x/peroxymonosulfate system

Recently, the [tbnd]Cu-OOSO₃^- metastable intermediate have been proposed to be the main active substance of contaminant oxidation, which could degrade organics through oxygen-atom-transfer and single-electron-transfer pathways. Herein, a series of copper cobalt oxides was synthesized to further explore its active species and electron-transfer pathways in the PMS activation system. The CuCo₂O_x precipitated a smaller nano-needle structure, more weak acid sites, and more Cu²⁺ and Co²⁺ contents on its surface. Notably, it exhibited excellent PMS activation performance due to the synergistic effect between Cu and Co. The single-electron-transfer pathway with radicals and singlet oxygen as active species participated in the oxidation reaction, and the oxygen-atom-transfer pathway also played an important role in the degradation of pollutants. Cu²⁺ was speculated to be the main active site for binding with PMS to form the [tbnd]Cu-OOSO₃^- active substances due to its strong complex ability. And the electron transfer of the Cu-O-Co bridge bond promoted an oxidation reaction between [tbnd]Cu-OOSO₃^- and the contaminant. Hence, this work provided new insights into the synergistic effect between Cu and Co sites and electron-transfer pathways of contaminants oxidation in the CuCo₂O_x/PMS oxidation system.