Analyzing Structural Changes of Fe-N-C Cathode Catalysts in PEM Fuel Cell by Mößbauer Spectroscopy of Complete Membrane Electrode Assemblies.
The applicability of analyzing by Mößbauer spectroscopy the structural changes of Fe-N-C catalysts that have been tested at the cathode of membrane electrode assemblies in proton exchange membrane (PEM) fuel cells is demonstrated. The Mößbauer characterization of powders of the same catalysts was recently described in our previous publication. A possible change of the iron species upon testing in fuel cell was investigated here by Mößbauer spectroscopy, energy-dispersive X-ray cross-sectional imaging, and neutron activation analysis. Our results show that the absorption probability of γ rays by the iron nuclei in Fe-N-C is strongly affected by the presence of Nafion and water content. A detailed investigation of the effect of an oxidizing treatment (1.2 V) of the non-noble cathode in PEM fuel cell indicates that the observed activity decay is mainly attributable to carbon oxidation causing a leaching of active iron sites hosted in the carbon matrix.
†Brandenburg Technical University of Cottbus - Senftenberg, Chair of Applied Physics and Sensors, Konrad-Wachsmann-Allee 17, 03046 Cottbus, Germany.
Ulrike I
UI
Kramm
‡Canetique Electrocatalysis, Inc., 1650 Boulevard Lionel-Boulet, Varennes, Québec J3X 1S2, Canada.
Michel
M
Lefèvre
§Helmholtz-Center Berlin for Materials and Energy, Hahn-Meitner-Platz 1, 14109 Berlin, Germany.
Peter
P
Bogdanoff
†Brandenburg Technical University of Cottbus - Senftenberg, Chair of Applied Physics and Sensors, Konrad-Wachsmann-Allee 17, 03046 Cottbus, Germany.
Dieter
D
Schmeißer
∥INRS-Énergie, Matériaux et Télécommunications, 1650 Boulevard Lionel-Boulet, Varennes, Québec J3X 1S2, Canada.
Jean-Pol
JP
Dodelet
ORR; PEM-FC; degradation; iron-based catalyst; iron−nitrogen−carbon catalyst; non-noble metal catalyst; nonprecious metal catalyst; oxygen reduction reaction; polymer electrolyte membrane fuel cell