Effect of hydrothermal reaction time and calcination temperature on properties of Au@CeO2 core-shell catalyst for CO oxidation at low temperature

摘要

Au@CeO2 core-shell nanostructure catalysts were synthesized by hydrothermal reaction method. The effect of hydrothermal reaction time and calcination temperature on the textural and morphological characteristics of the catalyst was investigated by TEM, SEM, XRD, XPS, ICP, UV-Vis, and N-2 adsorption-desorption techniques. The results proved that gold core and CeO2 shell formed simultaneously at the beginning of the reaction. By extending the hydrothermal reaction time, both the grain size of Au core and CeO2 shell increased. The crystallization degree of CeO2 and the interaction between Au and CeO2 were also enhanced. The 90 % CO conversion temperature (T-90 %) of Au@CeO2 declined from 187 to 142 degrees C with the hydrothermal reaction time extended from 6 to 20 h. After 70-h reaction, the catalytic activity was still maintained without any loss. The effect of the calcination temperature on the catalytic performance was also investigated and it turned out that high calcination temperature has a positive influence on the catalytic activity. The likely active sites are the interface between Au core and CeO2 shell. Gold content, metal-support interaction (MSI), and oxygen vacancy are all related to the activity. The excellent performance of 20 h-600 degrees C-Au@CeO2 in catalytic activity and stability results from the joint effects of these triple factors.