Synthesis and characterization of highly loaded Pt/carbon xerogel catalysts prepared by the Strong Electrostatic Adsorption method

Abstract

In order to decrease the mass transport limitations reported in classical PEMFC electrodes, Pt/carbon xerogel catalysts have great potential to replace Pt/carbon black catalysts. These nanostructured materials with well defined pore texture allow for better gas/water diffusion and better contact between the platinum particles and the ionomer (Nafion®). Pt/carbon xerogel catalysts with high metal content (~ 25 wt.%) and high metal dispersion (nanoparticles ca. 2 nm in size) were prepared via the ‘Strong Electrostatic Adsorption’ method; the impregnation-drying-reduction step with H2PtCl6 was repeated until the desired metal loading was achieved. However, both physico-chemical and electrochemical characterization show that the use of H2PtCl6 leads to Pt catalysts poisoned with chlorine, especially if the reduction temperature is lower than 450 °C. This induces a dramatic decrease of the Pt utilization ratio in the final PEMFC catalytic layer.