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

Abstract

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 °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).