Catalysts Made from Platinum Nanoparticles

Background

Supported catalysts are usually prepared by impregnating water soluble metal salts on a porous support, followed by drying, calcining and reduction. This produces well-dispersed catalysts with particles in the nm range having high activity and good thermal stability. However, the particle size distribution is wide and only limited control is achievable, making size-linked interpretation of catalytic mechanisms difficult. Therefore, for better control, different methods of preparation are under investigation.

Deposition of Platinum Nanoparticles Prepared in Water-in-Oil Microemulsions on g-Al₂O₃

Researchers in Sweden have examined the deposition of platinum nanoparticles, prepared in water-in-oil microemulsions, on g-Al₂O₃. In one method, based on work by Boutonnet et al, the g-Al₂O₃ was added to the platinum particle suspension and the microemulsion was then destabilised by adding tetrahydrofuran (THF), which deposited the platinum particles onto the support.

Transferring Stabilised Platinum Nanoparticles to an Aqueous Solution Before Adding g-Al₂O₃

In a second method, platinum nanoparticles were transferred to an aqueous solution and stabilised by a surfactant, prior to adding g-Al₂O₃. Both catalysts had high activity for CO oxidation by oxygen, but some particle agglomeration had occurred. This was due to a too rapid addition of THF, and inefficient redispersion of the primary platinum particles on transfer to the aqueous phase, respectively. Further work is suggested on the choice of pH, surfactant and control of the electrostatic interaction between the platinum particles and the g-Al₂O₃. 

Note: A complete list of references can be found by referring to the original text.

Source: Platinum Metals Review, July 2002, Volume 46, Number 3, page 105.

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