CO-OXIDATION CATALYZED BY NANOCRYSTALLINE CeO2 PARTICLES WITH DIFFERENT MORPHOLOGIES

Nanocrystalline cerium oxide (CeO2) particles prepared by the novel two-stage precipitation method were used for the catalysis of CO oxidation. Firstly, two shapes, i.e. particulate (P-) and needle-like (N-), CeO2 nanoparticles were formed via proposed temperature-arranged routes. The crystalline structure, morphology, particle size, and surface area of samples were characterized by using XRD, TEM, HRTEM, and BET techniques. Furthermore, the morphological effect of the CeO2 samples on the catalytic activity of CO oxidation was investigated. From the experimental results, it indicated that the prepared samples were all nonporous and fcc-structured CeO2. The CeO2 particles, as precipitating at 90°C for 5 min and then aging at 90°C, were particulate, whereas they were needle-like by aging at 0°C. The CO oxidation reaction showed that the catalytic activity of N-CeO2 nanoparticles was higher than that of P-CeO2, attributing from the exposed higher-energy {100} and {110} facets for N-CeO2 nanoparticles. Moreover, the calcined samples with higher degree of crystallinity showed further promotion in catalytic activity. It was also worthy to note, that by replacing the CeO2 catalyst by Pd/CeO2, a large increase in the CO conversion was found, especially catalyzed by Pd/N-CeO2.