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

Abstract

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 (O₂⁻) species at room temperature is fabricated and CO oxidation is used as a probe reaction for the exploration of the characteristics of surface O₂⁻ species on the CeO₂ surface. We discover that the surface O₂⁻ 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 O₂⁻ 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 O₂⁻ species and reveals the influences of these species in the whole redox circle of CO oxidation.