Investigation of oxygen vacancies on Pt- or Au-modified CeO2 materials for CO oxidation

Abstract

Metal (Au or Pt)-modified CeO₂ materials with excellent redox ability for the oxidation of CO to CO₂ were prepared by a redox precipitation method to investigate the role of surface oxygen vacancies. It was found that most of the Au or Pt was encapsulated by CeO₂. Both Au and Pt can effectively improve the reducibility of CeO₂ to form more oxygen vacancies at lower temperatures. The surface oxygen vacancies were thoroughly studied by UV-Vis spectroscopy, CO adsorption FTIR, H₂-TPR and CO pulse oxidation techniques. During the reaction cycle of CO oxidation, the oxygen vacancies were affected by the modified metals but played different roles in the performance of CO oxidation. There were more oxygen vacancies on Pt-CeO₂, which facilitated the formation of more carbonates. A certain amount (4.2%) of oxygen vacancies was necessary to improve the CO oxidation on this material. Comparatively, the rather fewer oxygen vacancies and the lower adsorption strength of carbonates did not affect the final elimination efficiency of CO on Au-CeO₂.