Influence of metal particles on the reduction properties of ceria-based materials studied by TPR

Temperature programmed reduction (TPR) investigations on ceria-based catalytic materials are presented. Pure ceria shows two major reduction regions around 790 K and 1100 K due to surface capping oxygen ions and bulk oxygen ions. The extent of reduction in the low temperature region depends greatly on the surface area of the sample. The remnant reduction features that appear below 700 K are ascribed to O2- ions located at various low coordination sites on the oxide crystallites. The substitution of ZrO2 (40-60%) in CeO2 lattice decreases the overall reduction temperature of high surface area samples. Metal particles supported on low surface area CeO2-ZrO2 solid solutions induce bulk reduction of the support at low temperatures to a great extent. These observations provide a clue that the CeO2-based oxide supports, irrespective of their surface area, can perform as good oxygen exchangers in the presence of metal particles, contributing indirectly to the overall catalytic activity.