A new understanding of CeO2-ZrO2 catalysts calcinated at different temperatures: Reduction property and soot-O2 reaction

Abstract

CexZr(1-x)O2 (x = 0.27, 0.50 and 0.73) mixed oxides were prepared by co-precipitation method and then aged at 700–1000 °C. The reducibility of the aged catalysts was investigated by H2-TPR. It was found that the changes in reduction properties are related to the Ce/Zr ratio and Ce0.27Zr0.73O2 shows an increased H2 consumption with aging temperature increasing, even 1000 °C-aged samples show an increased reduction ability. Raman, XPS and HRTEM reveal that the promotion on reduction property of the aged samples should be ascribed to the increase of surface oxygen species, surface Ce/Zr ratio, O-vacancies and (110) and (100) planes. However, this promotion can not obviously improve soot oxidation activity. XRD, BET and O2-TPD results reveal that textural, structural and oxygen desorption properties are crucial to soot oxidation activity. The poor contact between soot and active sites would be an important factor that leads to a contradiction between H2-TPR and soot-O2 reaction activity.