Activation of Various Fe-Based Precursors on Carbon Black and Graphite Supports to Obtain Catalysts for the Reduction of Oxygen in Fuel Cells

Three synthetic paths have been used to prepare iron-based catalysts for the electrochemical reduction of oxygen in solid polymer fuel cells. The catalyst precursor used in the first synthetic path was a dispersion of Fe(OH)2 on carbon black (Vulcan) that was reduced at 600°C in H2. The second synthetic path involved a method to intercalate FeC13 that was first used with graphite and then extended to Vulcan. The oxidized iron was reduced by either heating the resulting mate-rials at 600°C in 112 or by reacting them at room temperature with K-naphthalene in a nonaqueous solution. In the third synthetic path, Fe particles were generated directly on Vulcan by the reduction in a nonaqueous solution of FeC12 with triethylborohydride. All these iron containing materials were then activated at 1000°C in the presence of acetonitrile in order to transform them into active catalysts for °2 reduction. The best catalyst was obtained by extending the interca-lation method of FeC13 to carbon black (Vulcan) and then reducing the oxidized iron with K-naphthalene. Based on elec-trochemical and physicochemical analysis (mostly scanning electron microscopy and x-ray diffraction analysis) it is sug-gested that iron is included or intercalated in the carbon black particles. The higher catalytic activity of this material compared to the others is explained by the progressive release of the iron from the carbon black particles and its reaction with acetonitrile during the final thermal activation step at 1000°C