Eg Obital Occupancy-Dependent Intrinsic Catalytic Activity of Zn-Co-Mn Spinel Oxides for Peroxymonosulfate Activation

Transition metal (TM)-based spinel oxides have demonstrated excellent efficacy in Fenton-like reactions, but the existing model cannot fully explain the origin of catalytic activity. Here, we first discover a critical role of eg occupancy in governing the intrinsic activity of ZnCoxMn2-xO4 spinel oxides (x=0-2.0) for peroxymonosulfate (PMS) activation and pollutant degradation. The introduction of Co into ZnMn2O4 network lowers magnetic momentum, eg occupancy, and favors the overlap between TM eg and O 2p orbitals. ZnCo2O4 with optimal eg occupancy, favorable PMS binding strength, interaction capability, and radical desorption exhibits the best catalytic activity. Cyclic voltammetry (CV) and Density functional theory (DFT) corroborate that ZnMn2O4 (eg=0.97) exhibits inert activity due to weak affinity towards PMS. The eg occupancy from 0.43 in ZnCo2O4 to 0.77 in ZnCoMnO4 is found to weaken PMS binding. These useful insights may inspire the reasonable development of catalysts, assist the prediction and enhancement of catalytic activity.