Redox property of CeO2-TiO2 mixed oxide and Pd/CeO2-TiO2 catalyst

The CeO2-TiO2 mixed oxide and its corresponding supported catalyst Pd/CeO2-TiO2 with Ce/Ti molar ratio of 0.05 similar to 0.40 were prepared by sol-gel and supercritical fluid drying method. Their redox properties were investigated by means of H-2-TPR. For CeO2-TiO2 with low Ce/Ti ratio, ceria is finely dispersed on TiO2. When Ce/Ti ratio is higher than 0.10, the anatase phase TiO2 with large crystallite size and amorphous TiO2-CeO2 solid solution or its precursor coexist in the mixed oxide. Ceria in the mixed oxide is completely reduced at about 500 degrees C, while only 40% of surface ceria in pure CeO2 is reduced at 504 degrees C and the remnant bulk ceria need higher temperature (804 V) to get reduced. These may be ascribed to the synergistic effect between CeO2 and TiO2, which produces abundant structural defects and improves the redox property of CeO2 in CeO2-TiO2. The CeO2-TiO2 mixed oxide with Ce/Ti ratio of 0.20 exhibits the most evident synergistic effect between CeO2 and TiO2. In Pd/CeO2-TiO2, the interaction between I'd and the support leads to a significant decrease in ceria reduction temperature (< 150 degrees C). The H-2 consumption peak of PdO in H-2-TPR profiles shifts to higher temperature with the increase in Ce/Ti ratio due to the enhancement of the interaction between PdO and CeO2-TiO2.