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| - Preparation of Platinum/Carbon Aerogel Nanocomposites Using a Supercritical DepositionMethod
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| - Platinum/carbon aerogel (Pt/CA) nanocomposites were synthesized using a supercritical deposition method.Dimethyl(1,5-cyclooctadiene)platinum (II) (CODPtMe2) was dissolved in supercritical CO2 (scCO2) andimpregnated into porous organic and carbon aerogels. The impregnated aerogels were converted to Pt/CAcomposites by heat treatment ranging from 300 to 1000 °C in the presence of nitrogen gas. Both conventionaland high-resolution TEM micrographs showed a good distribution of fairly monodisperse Pt particles throughoutthe bulk of all the aerogel supports used. The nature and crystallinity of the particles were confirmed usingXRD. Increasing the reduction temperature increased both the crystal size and the polydispersity. Crystallitesizes as small as 1 nm were obtained at low reduction temperatures and the particles were single-crystalline.Particle sizes obtained from H2 and CO chemisorption measurements are consistent with those measuredfrom TEM images, indicating the accessibility of the surface of platinum crystallites. The adsorption isothermfor the scCO2−CODPtMe2−CA system was measured at 28 MPa and 80 °C and indicated a strong substrate-precursor interaction which was also corroborated by thermogravimetric analyses (TGA). The isotherms alsoshowed that Pt loadings as high as 40 wt % could be achieved. The results of this study demonstrated thatin SCF deposition, it is possible to control the dispersion of metal crystallites on various supports through thestrength of the interactions between metal precursors and the substrate and the reduction temperature.
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