Simultaneous Supercritical Deposition involves the dissolution of metal precursors in a supercritical fluid (SCF) and exposure of a substrate to this solution. Metal precursors are then physisorbed or chemisorbed on the support in the presence of SCF. Adsorbed metal precursors can then be decomposed to end up with supported metals or metal oxides through various processes. In this technique, adsorption process determines the amount of metals which can be deposited onto the support.Carbon aerogel supported Pt-Cu alloy nanoparticle fuel cell catalysts were prepared with thermodynamically controlled metal loading using the binary physisorption of - dimethyl(1,5-cyclooctadiene)platinum(II) (Pt(cod)me2) and bis(1,1,1,3,5,5,6,6,6-nonafluorohexane-2,4-diiminate)copper in the presence of supercritical CO2 (scCO2). Binary adsorption isotherms were successfully predicted using the Ideal Adsorbed Solution Theory by using single component adsorption isotherm parameters alone. Alloy nanoparticles were formed via the thermal decomposition of metal precursors. The alloying of Pt and Cu within the nanoparticles was characterized via XRD peak shifts at various Pt/Cu ratios, and XPS data pointed out that the surfaces of these Pt�Cu alloy nanoparticles were enriched in Pt. USY zeolite supported Ni-W hydrocracking catalysts were prepared via the binary chemisorption of tungsten hexacarbonyl (W(CO)6) and Nickel(II) acetylacetonate or bis(1,1,1,3,5,5,6,6,6-nonafluorohexane-2,4-diiminate)nickel in the presence scCO2. Materials were then calcined at ambient pressure. FTIR indicated the chemisorption of metal precusors on USY zeolites. XRF analysis showed an increase in the W loading with an increase in both the initial W(CO)6 concentration in scCO2 and the deposition time. TPD-NH3 suggested that at the same loading the acid site distribution was different from catalyst prepared by incipient wetness and the proportion of the stronger acid sites was higher for the catalysts prepared using SSCD (53.3% of the total acid sites) as compared to that of the incipient wetness (33.2% of the total acid sites).

Simultaneous supercritical deposition: An alternative route for the preparation of supported bimetallic catalysts for energy conversion technologies

246th National Meeting (2013)

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