Support effects on the structure and catalytic activity of mesoporous Ag/CeO2 catalysts for CO oxidation

Catalytic properties of Ag catalysts supported on mesoporous CeO2 prepared by hard-template method (CeO2-HP) and surfactant-template method (CeO2-SP) have been investigated for CO oxidation. The experimental results revealed that mesoporous CeO2-HP was the preferable support as compared to mesoporous CeO2-SP for Ag/CeO2 catalysts in CO oxidation. A 100% CO conversion was achieved at 65 degrees C for Ag/CeO2-HP, while that for Ag/CeO2-SP was at 150 degrees C. CeO2-HP with smaller crystals would interact with Ag more strongly than CeO2-SP and the well-ordered slitelike mesoporous structure formed on CeO2-HP was relatively conducive to the molecular diffusion compared with the pore structure of CeO2-SP. Besides, a large amount of O-2(-) species and oxygen vacancies, which played an important role in the stability and dispersion of silver, were formed on CeO2-HP. After Ag addition, there existed an interface interaction between Ag and CeO2 and a fraction of electrons have been transferred from Ag to CeO2 via the Ag-CeO2 interface. Ag was the main species on both Ag/CeO2 catalysts and a pretty good dispersibility for the silver species was observed on CeO2-HP. The addition of Ag on CeO2-HP was more capable of enhancing the reducibility of surface-capping oxygen of CeO2 and promoting the formation of active surface absorbed oxygen species. All of these properties, which were arisen from different preparation methods of supports, can be responsible for the superior CO catalytic activity on Ag/CeO2-HP catalyst. (C) 2013 Elsevier B.V. All rights reserved.