Interfacial SmMn synergy in Mn2O3 catalysts enables efficient toluene oxidation

Sm doping is an effective strategy to boost the catalytic activity of Mn 2 O 3 for gas-phase VOCs elimination through surface oxidation. Herein, a series of Sm y MnO x oxide composite catalysts (y = 0.02–0.05) were synthesized by the redox co-precipitation method and evaluated for the catalytic oxidation of toluene. Compared with pure Mn 2 O 3 , Sm y MnO x catalysts exhibited excellent activity and long-term stability, decreasing the temperature required for complete toluene conversion by 65, from 275 to 210 °C. Sm incorporation induces the formation of the Sm-O-Mn bridging bonds, which weaken intrinsic Mn O bonding strength and accelerate lattice oxygen migration. Correspondingly, the proportion of surface active Mn 4+ species rises from 21 to 38%, and adsorbed oxygen species increase from 29 to 41% for Sm 0.04 MnO x . The morphology, elemental distribution, and crystal structure of the catalysts were characterized by SEM, TEM, EDS and XRD, while their redox properties were examined via H 2 -TPR and O 2 -TPD, and surface active species were quantitatively analyzed using XPS. Appropriate Sm doping optimizes catalyst reducibility, improves toluene adsorption capacity and adsorption kinetics, and thus accelerates the whole oxidation cycle and decreases characteristic conversion temperatures. In situ DRIFTS measurements identify benzoic acid and benzoate as pivotal intermediates during toluene degradation. DFT calculations verify that interfacial electron transfer occurs from adsorbed oxygen to both Mn and Sm sites over Sm 0.04 MnO x , revealing the essence of Sm Mn synergistic catalysis. Overall, Sm 0.04 MnO x demonstrated stronger adsorption and activation abilities toward toluene compared with Mn 2 O 3 , clearly elucidating the promotional mechanism of Sm heteroatom doping and providing a facile strategy for designing high-efficiency Mn-based VOC elimination catalysts.