Platinum catalysts highly dispersed metallic

In the first membrane-type fuel cells, the dispersed platinum catalyst was pure metal because of its large consumption. Smaller consumption and a much more efficient utilization of the platinum catalyst were attained by depositing the metal on a highly disperse carbon carrier. The best results were attained by using Vulcan XC-72 furnace... 

The deposition-precipitation (DP) method has been scarcely used to prepare platinum supported catalysts [1-5], while it is the preferred method to obtain active gold ones [6-7]. Initially, the deposition-precipitation technique has been developed by Geus and Hermans for the production of highly loaded and highly dispersed metal/oxide catalysts [8]. This technique involves the precipitation of the active phase precursor at fte surface of Ae support and its subsequent deposition whereas nucleation in the solution itself should be avoided. 

For more than 10 years (138-143) it has been known that by reaction of dispersed Pt on soot with nonnoble metals of Group IV B and V B dispersed alloys are formed. Treating Pt-impregnated carbons, to which salts of these metals had been added, at 900°C in inert atmosphere (Ar) leads to formation of highly dispersed Pt-Cr or Pt-V alloys. The metal salt is reduced to the metal by the soot and forms the respective platinum alloy in situ. These alloy crystallites are reported to be highly active catalysts for phosphoric acid fuel cells. 

In addition, the same studies that were carried out on the Pt(lll) crystal face result in reaction rates identical to those found on stepped crystal surfaces of platinum. These observations support the contention that well-defined crystal surfaces can be excellent models for polycrystalline supported metal catalysts. It also tends to verify Boudart s hypothesis that cyclopropane hydrogenolysis is an example of a structure-insensitive reaction. The initial specific reaction rates, which were reproducible.within 10%, are within a factor of two identical to published values for this reaction on highly dispersed platinum catalysts. The activation energies that were observed for this reaction, in addition to the turnover number, are similar enough on the various platinum surfaces so that we may call the agreement excellent. 

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