Cerium-driven electronic modulation in CoMn₂O₄ spinel: Uniting lattice and gaseous oxygen pathways for accelerated toluene destruction

Efficient and stable catalysts are essential for the removal of volatile organic compounds (VOCs). This study reveals that the exceptional catalytic activity of cobalt-manganese spinel oxides for VOC oxidation is attributed to local electronic tuning, tailored through the selective substitution of non-active rare-earth species. Specifically, incorporating Ce into octahedral CoMn₂O₄ sites (forming CoMn_1.9Ce_0.1O₄), induces significant electronic modulation during toluene oxidation, resulting in a remarkably increased activity (T₉₀ = 248 °C, a 58°C reduction compared to the undoped system) and sustained long-term stability (>30 h). In situ DRIFTS studies reveal that this tuning synchronously activates lattice oxygen and promotes gaseous oxygen adsorption, accelerating the rate-determining conversion of maleic anhydride intermediates within the Mars-van Krevelen mechanism, thus driving a synergistic catalytic cycle coupling lattice oxygen and gaseous oxygen pathways. In situ characterization and theoretical calculations further demonstrate that octahedrally coordinated Ce ions, occupying octahedral coordination sites, function as atomic-scale electronic modulators, inducing lattice charge redistribution, enhancing metal-oxygen ligand covalency, and increasing oxygen vacancy concentrations. This process optimizes adsorption energetics for oxygen intermediates and lowers activation energy barriers for gaseous oxygen dissociation at the interface. This work establishes a 4f-block doping strategy for spinel catalysts, which activates dual oxygen pathways and provides an atomic-level design principle for superior VOC oxidation.