Analysis of catalytic activity of novel cathode catalyst for fuel cells using polymer-cobalt complexes

Oxidative polymerization of pyrrole onto a surface of a carbon particle dispersed in an electrolyte solution was performed using a fluid-bed electrode where the carbon particle served as a working electrode. Complexation of the polypyrrole (PPy)-modified carbon particle with a cobalt ion by a heterogeneous process proceeded irreversibly and almost quantitatively to give a Co-PPy complex-modified carbon particle, which proved to be a good catalyst for the electro-reduction of oxygen. Voltammetric analysis using an electrode modified with a Nafion film containing the catalyst revealed that oxygen was reduced by four electrons at a high peak potential. Heat treatment of the catalyst greatly improved the catalytic activity. The improvement in the activity was ascribed to the decrease in the size of the active site, which led to a closer packing of the catalyst at the carbon surface. The high activity and the stability suggested that the catalyst can be used as an alternative to the conventional Pt/C catalyst in fuel cells. This is an abstract of a paper presented at the 229th ACS National Meeting (San Diego, CA 3/13-17/2005).