Structure of the catalytic sites in Fe/N/C-catalysts for O2-reduction in PEM fuel cells.

Fe-based catalytic sites for the reduction of oxygen in acidic medium have been identified by (57)Fe Mössbauer spectroscopy of Fe/N/C catalysts containing 0.03 to 1.55 wt% Fe, which were prepared by impregnation of iron acetate on carbon black followed by heat-treatment in NH(3) at 950 °C.

Unveiling N-protonation and anion-binding effects on Fe/N/C-catalysts for O reduction in PEM fuel cells.

The high cost of proton-exchange-membrane fuel cells would be considerably reduced if platinumbased catalysts were replaced by iron-based substitutes, which have recently demonstrated comparable activity for oxygen reduction, but whose cause of activity decay in acidic medium has been elusive. Here, we reveal that the activity of Fe/N/C-catalysts prepared through a pyrolysis in NH is mostly imparted by acid-resistant FeN-sites whose turnover frequency for the O reduction can be regulated by fine chemical changes of the catalyst surface. We show that surface N-groups protonate at pH 1 and subsequently bind anions.