Preparation of Platinum-Nafion-Carbon Black Nanocomposites via a Supercritical Fluid Route as Electrocatalysts for Proton Exchange Membrane Fuel Cells

Novel platinum-Nafion-carbon black nanocomposites were synthesized using supercritical deposition. The method consists of preparation of a Nafion-carbon black composite followed by impregnation of a platinum precursor (PtMe2COD) into the composite via adsorption from a solution of supercritical carbon dioxide. Subsequently, the impregnated composite is subjected to thermal treatment resulting in a platinum-Nafion-carbon black composite. The platinum-Nafion-carbon black composite was characterized by hydrogen chemisorption, and the average size of the platinum metal particles was found to be around 2.6 nm. A preliminary cyclic voltammetry test demonstrated that the composite displayed promising electroactivity as an electrocatalyst for proton exchange membrane fuel cells. To investigate the effects of the impregnation under supercritical conditions at high pressures and subsequent thermal reduction at elevated temperatures on the Nafion structure, composite films of platinum-Nafion 112 were prepared by the same supercritical deposition method. The infrared spectra of the films indicated that the structure of Nafion 112 did not change significantly during processing.