Construction of electron-rich Co centers and abundant redox pairs in MnO2/CoMn2O4 heterointerfaces for PMS activation and water purification

Abstract

Multiphase catalysts with heterointerfaces have shown compelling potential in catalyzing oxidative mineralization of pollutants. In particular, the interfacial electron communication of heterointerfaces is beneficial for activation of reactant molecules through promotive interfacial electron transfer efficiency. In this study, a MnO₂/CoMn₂O₄ heterojunction catalyst was constructed for the electron-rich Co centers and abundant redox pairs. Benefiting from the synergistic interaction between cobalt (Co²⁺/Co³⁺) and manganese (Mn²⁺/Mn³⁺/Mn⁴⁺) at the active sites, as well as the electron density difference between the interfaces of the two phases, a significant enhancement of the catalytic activity for peroxymonosulfate (PMS) activation was achieved. Systematic characterization analysis revealed that the catalyst has highly active catalytic sites characterized by electron-rich Co²⁺, and the electron-donating property of the high-electron-density Co²⁺ active sites in the A site of spinel CoMn₂O₄ promotes the efficient transfer of electrons and the rapid generation of reactive oxygen species (ROS) from PMS activation. More exposed catalytic active sites and significantly lower interfacial mass transfer resistance further enhanced the activation performance of the catalysts for bisphenol A degradation by these ROS. The optimal MnO₂/CoMn₂O₄–5 exhibited a optimal BPA degradation activity (86 %, k_obs = 0.316 min^-1) and excellent resistance to anionic interference. The results of free radical quenching experiments indicated that single linear oxygen (¹O₂) and hydroxyl radical (·OH) were the main active substances for PMS activation and BPA degradation. This study provides meaningful insights into the improvement of heterojunction interfacial systems for catalytic efficiency enhancement and environmental remediation.