Fe-based electrocatalysts made with microporous pristine carbon black supports for the reduction of oxygen in PEM fuel cells

Abstract

Fe-based catalysts for the oxygen reduction reaction at the cathode of polymer electrolyte membrane (PEM) fuel cells have been prepared using several highly microporous (defined as pores having a size <2 nm) carbon supports. The aim is to produce better performing catalysts as it is known that catalytic sites are hosted in the micropores of the carbon supports. All catalysts were loaded with a nominal Fe content of 0.2 wt% and were obtained by heat-treatment at 950 °C in pure NH 3 atmosphere. It is demonstrated, however, that the use of highly microporous carbon supports does not lead to improved catalytic activity, as originally expected, since the surface of these micropores is devoid of the nitrogen functionalities necessary to build the catalytic sites. Also, it is shown that for these microporous carbon supports, it is only the new micropores, i.e. those created during NH 3 etching at high temperature, that are capable of hosting catalytic sites.