Applied Catalysis A: General, Vol.364, No.1-2, 143-149, 2009
Structures and CO oxidation activities of size-selected Au nanoparticles in mesoporous titania-coated silica aerogels
We have prepared Au/Titania-coated silica aerogel catalysts from Au nanoparticles (AuNPs) having well-regulated sizes in the range 1.4-6.4 nm, through heat-treatment of thiol-capped AuNPs, size-separation through fractional precipitation, and adsorption of the AuNPs on the support in a nonpolar solvent. The Au particle size was preserved during calcination of the catalyst samples at 673 K and subsequent CO oxidation. The turnover frequency for CO oxidation of the catalysts changed drastically when their sizes varied from 4 to 5 nm, but it did not change appreciably in other size regions. X-ray absorption spectroscopy and X-ray diffraction measurements revealed that lattice contraction and structural changes become prominent at Au diameters of less than 4-5 nm. Thus, the structural changes that occurred in the AuNPs in this diameter region are consistent with the enhanced catalytic activity. (C) 2009 Elsevier B.V. All rights reserved.