Oxygen Reduction in PEM Fuel Cells: Fe-Based Electrocatalysts Made with High Surface Area Activated Carbon Supports

Catalysts for the oxygen reduction reaction in polymer electrolyte membrane (PEM) fuel cells were prepared by impregnating four high surface area activated carbons (ACs), namely, Ax-21, CNS-201, IRH-33, and IRH-40, with 0.2 wt % nominal Fe as ferrous acetate, and then by pyrolyzing them for various times in at . Among the catalysts made with as-received ACs, high activity was only obtained for those made with Ax-21, which is the only AC having mainly carboxylate surface groups. In the aerated aqueous solution of iron(II) acetate used for Fe impregnation, these surface functionalities ligated with free ions and subsequently yielded active sites upon pyrolysis in . It is, nonetheless, possible to obtain high activities using other ACs provided that they are first treated in concentrated to generate carboxylic functionalities at their surface. It is believed that Fe/N/C-type catalytic sites are hosted in AC micropores. Fuel cell tests performed with the best catalyst from each AC series show very similar polarization curves with an initial mass activity at 0.8 V ranging from 11 to .