Fe/N/C catalysts for the reduction of oxygen in PEM fuel cells were prepared by pyrolyzing three series of iron acetate-impregnated developmental carbon blacks at 950 degrees C. The carbon supports used were derived from the N234. N330, and N650 commercial furnace grades. In this Study, we tried to increase the performance of Fe/N/C-based cathode of PEM fuel cells by using the following two approaches: (1) increasing the number of catalytic sites on the carbon black either by optimizing the structural parameters of the pristine carbon Supports or by increasing the initial metal content above 0.2 wt% Fe on the carbon support: (2) increasing the catalyst loading in the cathodic layer of a PEM fuel cell. For (1), we show, on the one hand. that optimizing the structural parameters of the pristine carbon support, in order to increase the number of catalytic sites. has its limits and that these limits have been reached for the present synthesis method of Fe/N/C catalysts. On the other hand, increasing the initial metal Content above 0.2 wt% Fe leads to a decrease in catalytic activity. For (2). it is shown that increasing the catalyst loading per cm(2) of cathode well improves the performance of a cathode based oil Fe/N/C catalysts in the kinetic region of the polarization curve. At lower potentials, a large improvement in the performance of these non-precious metal cathodes would occur if the mass transport properties in these electrodes were significantly increased. (c) 2008 Elsevier Ltd. All rights reserved.