Probing different effects of surface MOy and Mn+ species (M = Cu, Ni, Co, Fe) for xMOy/Ce0.9M0.1−xO2−δ catalysts in CO oxidation

• Surface MOy species on the Ce-M catalysts could be removed by acid treatment.
• The activities of HCe-M catalysts were suppressed.
• MOy species promoted the chemisorption of CO molecules.
• Oxygen vacancy facilitated the activation of oxygen.
• Synergetic effect could improve the activity of catalysts.

A series of xMOy/Ce0.9M0.1−xO2−δ (M = Cu, Ni, Co, Fe) catalysts (Ce-M) were prepared by a sol–gel method and corresponding Ce0.9M0.1−xO2−δ catalysts (HCe-M) were obtained with an acid treatment. It was found that the Ce-M catalysts contained surface MOy species and Ce0.9M0.1−xO2−δ solid solution, as confirmed by the results of X-ray diffraction and Raman spectra, respectively. While the HCe-M catalysts only contained Ce0.9M0.1−xO2−δ solid solution. CO oxidation over these catalysts revealed that the activities followed an order of Ce-Cu > Ce-Ni > Ce-Co > Ce-Fe, but were remarkably higher than the corresponding HCe-M samples. The activities of the HCe-M catalysts were closely related to their reducibility originated from the oxygen vacancies in these samples. The most active HCe-Cu catalyst had the highest content of oxygen vacancies and thus was the most reducible. For the Ce-M catalysts, the enhanced catalytic performance was due to a synergy between the surface MOy species and the Ce-M-O solid solution, as the former provided sites for CO chemisorption and the latter promoted the activation of oxygen.

The enhanced activities of xMOy/Ce0.9M0.1−xO2−δ (M = Cu, Ni, Co, Fe) catalysts for CO oxidation were due to the synergetic effects of surface MOy species and Ce-M-O solid solution, as the former facilitate the CO chemisorption and the latter promoted the oxygen activation.Figure optionsDownload as PowerPoint slide