H2/O2 PEM fuel cell current density curves of Fe/N/C catalysts at 0.6V and 80xA0;°C show a fast decay of about 15h. H2O2 is not the cause of the fast decay, either by direct or indirect (Fenton) reaction with the catalytic sites. The electro-oxidation of the catalyst’s carbon supports induces water flooding in these initially hydrophobic catalysts. The characteristics of a catalyst that would perform ORR with a large majority of CNx catalytic sites were also defined.