Silica-Supported Au Nanoparticles Decorated by CeO2: Formation, Morphology, and CO Oxidation Activity

SiO2-supported Au nanoparticles derived from sol were promoted with 0.04-7.4 wt % CeO2 using two methods. The addition of Ce precursor was done directly to the Au sols before sol immobilization step (method A) or to the suspension of parent Au/SiO2 (method B). Both preparation routes resulted in CeO2 decoration of 1-3 nm over Au nanoparticles, which induced high CO oxidation activity. However, above 0.6 wt % CeO2 content, the activity did not change significantly, but it greatly exceeded that of pure Au/CeO2 used for reference. High-resolution transmission microscopy (HRTEM) showed that up to this concentration ceria patches are attached onto gold surface, and the further increase in Ce-loading caused CeO2 spread over the support surface as well. Strong interaction of Ce species with stabilizer ligands located around Au is suggested as the reason for CeO2 localization on gold.