CARBON-MONOXIDE POISONING OF PLATINUM-GRAPHITE CATALYSTS FOR POLYMER ELECTROLYTE FUEL-CELLS - COMPARISON BETWEEN PLATINUM-SUPPORTED ON GRAPHITE AND INTERCALATED IN GRAPHITE

Platinum intercalated in graphite and Pt supported on graphite have be en synthesized as catalysts for polymer electrolyte fuel cells in orde r to test the effect of carbon monoxide adsorption on their electroche mical properties. These materials have been characterized by X-ray dif fraction, scanning electron microscopy, neutron activation analysis an d cyclic voltammetry in Nafion-based films in contact with H2SO4 solut ion at pH 0.5. Pt intercalates are indeed tridimensional Pt cluster in clusions in a perturbed graphite matrix. Hydrogen electrosorption meas urements demonstrate that Pt supported on graphite has three times mor e active sites than Pt intercalated in graphite even if Pt loadings (1 6 +/- 4 Pt wt.%) and the size of Pt clusters (3.4 +/- 0.4 nm) are simi lar for both catalysts. Pt supported on graphite and intercalated in g raphite are equally poisoned by carbon monoxide.