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FUEL CELL CATALYSTS.
Quarterly rept. no. 2, 1 Aug-31 Oct 65,
ENGELHARD INDUSTRIES INC NEWARK N J RESEARCH AND DEVELOPMENT DIV
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A series of potential catalyst carriers was investigated studying various carbon powders of increasingly graphitic structure and a fine grid boron carbide sample Norbide F 1500. This group of carriers is primarily of interest for catalysts for the fuel electrode. Any utility for the air electrode is limited to temperatures not much above ambient since rapid oxidation of the carrier occurs in contact with platinum catalyst. Relatively small precious metal cystallite sizes are obtained on the boron carbide sample and, similarly on catalysts supported on graphite carriers. This is ascribed to a particular surface structure. At high metal to carrier ratios the distribution of the precious metal crystallites on graphite and boron carbide, is less uniform than desirable. Electron micrographs show the crystallites to be arranged in large aggregates. An even distribution into essentially individual crystallites is obtained on carbon supports of higher surface area. Small platinum metal crystallite sizes or a high degree of metal dispersion do not necessarily correlate with the ultimate performance of the catalyst. Additional factors may be significant. Author
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