Effect of strong interaction between Co and Ce oxides in Co_xCe_1-xO_2-δ oxides on its catalytic oxidation of toluene

A series of Co_xCe_1-xO_2-δ (x = 0.05−0.6) oxides were synthesized through non-ionic surfactant hydrothermal method and applied for catalytic toluene oxidation. Various characterizations were performed to investigate the relation between structure and activity of the catalysts, including XRD, N₂ adsorption-desorption, Raman spectra, TEM, H₂-TPR, O₂-TPD, XPS and in situ DRIFTS. Co_xCe_1-xO_2-δ shows higher catalytic performance than pure Co₃O₄ and CeO₂, meanwhile Co_0.2Ce_0.8O_2-δ exhibits the best catalytic activity for toluene oxidation in the presence and absence of water, moreover, no obvious difference in activity among three successive testing runs. This good activity can be mainly attributed to the strong interaction between Co and Ce oxides to form Co_0.2Ce_0.8O_2-δ solid solution, leading to abundant surface active oxygen species, more surface Co³⁺ and Ce³⁺ species. In situ DRIFTS is used to probe the catalytic reaction process, which reveals that toluene can be rapidly adsorbed and transferred to benzoate species, finally oxidized into CO₂ and H₂O.