Pt/CeO(2)-ZrO(2) present in the mesopores of SBA-15--a better catalyst for CO oxidation.

Platinum loaded CeO(2)-ZrO(2)/SBA-15 composite material catalyzes CO oxidation at lower temperatures (<100 degrees C) than conventionally prepared Pt/CeO(2)-ZrO(2) (>150 degrees C). A sequence of reduction and reoxidation of CeO(2)- and ZrO(2)-loaded samples promotes the formation of CeO(2)-ZrO(2) solid solution on the siliceous surface as indicated by wide-angle X-ray diffraction (XRD) patterns. Furthermore, initial coating of ZrO(2) on the silica walls is quite important before CeO(2)-ZrO(2) loading in order to obtain the CeO(2)-ZrO(2) solid solution. The presence of CeO(2)-ZrO(2) particles inside the mesopores is confirmed by N(2) adsorption, low-angle X-ray diffraction, and scanning transmission electron microscopy (STEM) images. The solid solution of CeO(2)-ZrO(2) in the confined mesoporous space forms more Ce(3+) centers associated with oxygen vacancies on the surface due to the smaller size of the dispersed particles and these Ce(3+) centers are believed to be responsible for the higher catalytic activity.