e_g Orbital Occupancy-Dependent Intrinsic Catalytic Activity of Zn-Co-Mn Spinel Oxides in Fenton-like Reactions

Transition-metal (TM)-based spinel oxides have demonstratedexcellentefficacy in Fenton-like reactions, but the key mechanism behind peroxymonosulfate(PMS) adsorption, decomposition, and pollutant degradation is stillunclear. Here, a crucial role of e(g) orbital occupancy inmanipulating the interaction between PMS and Zn-Co-Mnternary spinel catalysts and the resulting pollutant degradation isfirst discovered. The introduction of Co into the ZnMn2O4 network lowers the magnetic momentum and e(g) occupancy and favors the overlap between TM e(g) and O2p orbitals. Experimental results demonstrate that the e(g) occupancy-dependent catalytic activity and pathway originate fromits cascade effect on PMS binding, decomposition, and radical desorption.Zn-Co-Mn with optimized e(g) occupancy exhibitsfavorable PMS binding strength, interaction capability, radical desorption,and pollutant degradation. Cyclic voltammetry (CV) and density functionaltheory (DFT) corroborate the critical role of e(g) in PMSaffinity. In addition, the ZnCoMnO4/PMS system shows highselectivity for carbamazepine (CBZ, 0.275 min(-1))and environmental robustness. The surface active complex PMS*, theperoxymonosulfate radical, and the sulfate radical are identifiedas reactive species. This work provides an intrinsic mechanism behindpollutant degradation and offers guidance for performance enhancementin a water environment. Thee(g) orbital occupancy-dependent catalyticactivity and pathway originate from its cascade effect on peroxymonosulfatebinding, decomposition, and radical desorption.