Probing the role of surface activated oxygen species of CeO2 nanocatalyst during the redox cycle in CO oxidation

The oxygen species of CeO2 nanocatalysts plays a key role in the CO oxidation. In this work, nanocrystalline CeO2 with infrared spectroscopy detectable surface superoxide (O-2(-)) species at room temperature is fabricated and CO oxidation is used as a probe reaction for the exploration of the characteristics of surface O-2(-) species on the CeO2 surface. We discover that the surface O-2(-) species have ignorable influences on the overall reaction rate of CO oxidation on pure ceria by comparing P-CeO2 (CeO2 prepared by precipitation method) with HT-CeO2 (CeO2 prepared by hydrothermal method). It is concluded that the reaction between CO molecules and surface O-2(-) species is the first and the fast step in the whole redox cycle, while the release of surface lattice oxygen is the second and the rate determining step of the catalysts. This work gives an intuitionistic exploration on the redox properties of pure nanocrystalline CeO2 with surface O-2(-) species and reveals the influences of these species in the whole redox circle of CO oxidation.