FUEL CELL CATALYSTS.
Rept. no. 4 (Final) 1 May 65-30 Apr 66,
ENGELHARD INDUSTRIES INC NEWARK NJ
Pagination or Media Count:
Mathematical analysis of mass transport conditions to the catalyst pore walls showed wide and short pores to be the desirable geometric configuration. Optimum numerical values of length and radius are dependent on diffusivity and reaction rate constant. Carbonaceous carriers including carbon blacks, graphites and boron carbides, are suitable for anodic service but, in conjunction with precious metals, are oxidized at the cathode. The bulk density, surface area, particle size and shape, electrical conductivity and pore structure of carriers have been examined, as well as the state of dispersion and the adherence of deposited platinum or platinum-ruthenium catalysts at various metal to carrier and platinum to ruthenium ratios. Comparable metal crystallite size reduction can be obtained on all carriers despite large differences in surface areas. Crystallite size also decreases with decreasing metal to carrier ratios. Alloying with ruthenium reduces the platinum crystallite size, but to a lesser degree than in the case of unsupported metal. Lower metal to carrier ratios and higher carrier surface areas generally improve the uniformity of the metal dispersion. However, small crystallite size and uniform metal distribution do not always coincide. The oxidation of methanol, or propane, iso-octane and carbon monoxide containing hydrogen in sulfuric, or phosphoric acids is improved by the use of supported anode catalysts. Precious metal utilization increased up to four fold at practical current densities. Alloying suported platinum with ruthenium was beneficial for the oxidation of methanol, whereas unalloyed supported platinum is preferred for the oxidation of propane.
- Physical Chemistry