CO-OXIDATION CATALYZED BY NANOCRYSTALLINE CeO2 PARTICLES WITH DIFFERENT MORPHOLOGIES

Abstract

Nanocrystalline cerium oxide ( CeO 2) 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-), CeO 2 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 CeO 2 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 CeO 2. The CeO 2 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- CeO 2 nanoparticles was higher than that of P- CeO 2, attributing from the exposed higher-energy {100} and {110} facets for N- CeO 2 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 CeO 2 catalyst by Pd / CeO 2, a large increase in the CO conversion was found, especially catalyzed by Pd /N- CeO 2.