Thermogravimetry/Mass Spectrometry Investigations on the Formation of Oxygen Reduction Catalysts for PEM Fuel Cells on the Basis of Heat-Treated Iron Phenanthroline Complexes

Oxygen reduction catalysts for PEM fuel cells on the basis of carbon supported, heat-treated iron phenanthroline complexes have been investigated with rotating disc-electrode (ROE) measurements and with thermogravimetry/mass spectrometry (TG/MS). It has been found, that the slope of the Koutecky-Levich plot from RDE measurements changes with electrode potential and with catalyst loading of the electrode. The results can be understood in terms of a two times 2-electron reduction of oxygen at the iron-based catalysts. TG/MS indicate, that during the heat-treatment step the phenathroline molecule of the catalyst precursor is completely embedded into the carbon. The results are discussed in terms of the structure of the active centre of these catalysts.