Platinum-silica aerogels via supercritical drying and impregnation

The preparation of a platinum (Pt)-silica aerogel nanocomposite has been investigated using supercritical impregnation of platinum (II) acetylacetonate (Pt(II)(acac)(2)) into silica substrate. The Pt(II)(acac)(2) was dissolved in supercritical carbon dioxide (scCO(2)) and was impregnated into the silica gel during the supercritical drying stage. Due to low viscosity, high diffusivity, and weak interactions with the dissolved Pt complex, scCO(2) can yield a good dispersion of Pt particles at short treatment times. A number of silica aerogels were prepared with differing surface roughness and degree of hydrophobicity in order to investigate how the surface of the substrate would affect the loading of Pt per sample. The use of tetrahydrofuran during the aerogel preparation stage to affect the solubility of Pt(II)(acac)(2) was also investigated. Platinum-silica aerogels were successfully prepared with Pt contents up to 1.59 wt% and an average particle size <10nm. We discuss the effects of the impregnating conditions and of the modification of the substrates as described above. (C) 2004 Elsevier B.V. All rights reserved.