Surfactants-assisted synthesis and characterizations of multicomponent mesoporous materials Co–Ce–Zr–O and Pd/Co–Ce–Zr–O used for low-temperature CO oxidation

The multicomponent mesoporous materials Co–Ce–Zr–O with different atomic ratios of Co/Ce were prepared by using the mixed surfactants consisting of nonionic p-octyl polyethylene glycol phenyl ether (OP) and cationic cetyltrimethyl-ammonium bromide (CTAB) as co-templates. The results of N2 adsorption/desorption show that these materials possess not only large specific surface areas above 100 m2 g−1 but also uniform mesoporous pore diameter centered at 4.6 nm. The structural characterization results of XRD and XPS indicate that the highly dispersed Co3O4 crystallites should be the main active phase for CO oxidation. The change of Co/Ce atomic ratio shows little influence on the specific surface areas of the samples whereas it apparently affects the interaction between cobalt and cerium phase. When Co/Ce ratio is 1:1, the catalyst shows the best performance for CO oxidation due to its highest oxygen mobility and surface enrichment of cerium species, as confirmed by H2-TPR and XPS, respectively. When ultra-low amount of Pd (0.044 wt%) is added to Co–Ce–Zr–O, the temperature for the full conversion of CO is only 97 °C, about 43 °C lower than that without Pd. This great activity enhancement of Pd can be ascribed to oxygen spillover during oxidation reaction, which has been clearly evidenced by O2-TPO results.