CoMnxOy nanosheets with molecular-scale homogeneity: an excellent catalyst for toluene combustion

The process driven by redox-precipitation reactions between Mn7+, Co2+ and Mn2+ can yield CoMnxOy nanosheet catalysts with (quasi) molecular scaled dispersed compounds which can achieve excellent catalytic activity in toluene combustion with T-50 (temperature of 50% toluene conversion) values of 172 degrees C and 218 degrees C (GHSV = 67500 h(-1) and 540 000 h(-1), respectively). The as-prepared CoMnxOy nanosheets demonstrated high specific surface area, and their overall morphology changed when Mn2+ was substituted with Mn7+ during the preparation process. The enhanced catalytic performance in toluene combustion can be ascribed to very high amounts of oxygen electrophilic species (O-/O-2(-)), as evidenced by XPS, H-2-TPR and O-2-TPD. In addition to the MnCo(2)O(4.)5 phase, Co3O4 formation can further improve the catalytic properties. According to TEM observations, the Co3O4 species were well dispersed on MnCo2O4.5 and strongly interacted with MnCo2O4.5 by forming an active Co3O4-MnCo2O4.5 interface. Toluene adsorption and O-2 dissociation could occur at the active interface by creating abundant oxygen vacancies, further providing adequate O-2(2-) species to take part in toluene oxidation. The influences of water vapor and other VOCs in simulated exhaust were also evaluated. The excellent performance of the catalysts in catalytic toluene combustion demonstrates that they have great potential for practical applications.