The effect of different metal oxides on the catalytic activity of a Co3O4 catalyst for toluene combustion: importance of the structure-property relationship and surface active species

Herein, Co3O4 catalysts modified with different metals M (M = La, Mn, Zr and Ni) were used in the catalytic combustion of toluene to demonstrate the importance of the structure-property relationship and surface active species. The results revealed that the Co-La catalyst exhibited optimum catalytic performance and CO2 selectivity, and 90% toluene conversion was obtained at 243 degrees C, which might be closely related to the formation of the LaCoO3 perovskite. Furthermore, the specific surface area, pore volume and low-temperature reducibility over these samples decreased as follows: Co-La > Co-Mn > Co-Zr > Co-Ni; this was completely consistent with the catalytic activity results. In addition, the Co-La sample possesses the most Co3+ species and abundant adsorbed oxygen species; this indicates that this sample has excellent oxygen storage capacity. Note that Co-Ni possesses the highest O-ads/O-latt ratio but exhibits the lowest activity; this infers that the active species Co3+ and O-ads participate cooperatively in the redox reaction. In brief, its excellent catalytic activity can be significantly attributed to its high specific surface area, excellent low-temperature reducibility and more abundance of surface active species (Co3+ and O-ads).