Role of CeO2 in Three-Component Au/CeO2/SiO2 Composite Catalyst for Low-Temperature CO Oxidation

Hierarchical composite nanostructure composed of Au, CeO2, and SiO2 was fabricated by sequentially depositing ceria nanoparticies through impregnation and calcination, and then gold nanoparticles through a deposition-precipitation method on hierarchical monolithic silica (HMS) with multi-length scale pore structure. The Au/CeO2/HMS composite nanostructure was characterized by X-ray diffraction, temperature-programmed reduction, and diffuse reflectance infrared Fourier transform spectroscopy. The results indicate that the presence of ceria had a significant effect on targeted deposition and stabilization of small metallic gold nanoparticles on the support. The temperature for complete conversion of CO to CO2 over Au/CeO2/HMS is ca. 60 degrees C at a space velocity of 80000 ml/(g.h). The highly dispersed metallic gold nanoparticles can activate CO and the small ceria nanoparticles supply oxygen in the reaction. The catalytic activity remains considerably stable during 48 h stability testing. The interaction between gold and ceria contributed greatly to CO oxidation and the presence of silica improved the stability of the gold catalyst.