Characterization and Electrocatalytic Activity of Carbon-supported Polypyrrole-Cobalt-Platinum Compounds

In this paper we report on the physical and electrochemical characterization of carbon-supported materials based on polypyrrole, cobalt and platinum as electrocatalysts for the oxygen reduction reaction (ORR) in PEM fuel cells. Polypyrrole was polymerized onto carbon black (thermally treated at 450oC), and modified with cobalt and/or platinum salts, to obtain carbon-polypyrrole-cobalt, carbon-polypyrrole-platinum and carbon-polypyrrole-cobalt-platinum composites. For comparison, results for unmodified polypyrrole are also reported. It was shown by XRD that the metal-containing materials contain metallic particles within the amorphous polymer samples. The morphology of the composite materials is similar to the carbon support. The platinum-containing materials contain 7% in weight of this element, cobalt-treated materials have 4% in weight of cobalt, and those treated with both salts shows 4% in weight of both metals. Thermal stability was confirmed up to temperatures above 200 °C. It was shown that all materials have electrocatalytic activity for the oxygen reduction reaction (ORR), with the carbon-polypyrrole-platinum compound (C-Ppy-Pt) showing ORR occurring at highest potentials (+0.80 V), due to the presence of platinum. Electrochemical stability was confirmed for the ORR in acid medium. The composite materials were applied as PEMFC cathode catalyst, showing best fuel cell performance for C-Ppy-Pt.