Co3O4 particles grown over nanocrystalline CeO2: influence of precipitation agents and calcination temperature on the catalytic activity for methane oxidation.

摘要

Crystalline cobalt oxides were prepared by a precipitation method using three different precipitationudagents, IJNH4)2CO3, Na2CO3 and COIJNH2)2. Cobalt oxide nanoparticles corresponding to a Co3O4 loadingudof 30 wt% were also deposited over high-surface area nanocrystalline ceria by the same precipitationudagents. The effect of calcination temperature, 350 or 650 °C, on the morphological and structural propertiesudwas evaluated. Characterization by BET, XRD, SEM, TEM, Raman spectroscopy, H2-TPR, XPS andudNH3-TPD was performed and the catalytic properties were explored in the methane oxidation reaction.udThe nature of the precipitation agent strongly influenced the textural properties of Co3O4 and theudCo3O4–CeO2 interface. The best control of the particle size was achieved by using COIJNH2)2 thatudproduced small and regular crystallites of Co3O4 homogeneously deposited over the CeO2 surface. Such audCo3O4–CeO2 system precipitated by urea showed enhanced low-temperature reducibility and high surfaceudCo3+ concentration, which were identified as the key factors for promoting methane oxidation atudlow temperature. Moreover, the synergic effect of cobalt oxide and nanocrystalline ceria produced stableudfull conversion of methane in the entire range of investigated temperature, up to 700–800 °C, at whichudCo3O4 deactivation usually occurs.