Implementation of different Fe–N–C catalysts in high temperature proton exchange membrane fuel cells – Effect of catalyst and catalyst layer on performance

Abstract

Fe–N–Cs are an alternative to Pt/C catalysts as they show promising activity towards the oxygen reduction reaction. While several studies are based on thin-film analysis in diluted electrolytes, only few reports show the application of Fe–N–Cs in gas diffusion electrodes (GDE) and their tests under high temperature proton exchange membrane fuel cell (HT-PEMFC) conditions. Here, a series of Fe–N–Cs with different physical properties are analyzed. GDEs are fabricated using ultrasonic spray and doctor blade coating to investigate the effect of coating method on the morphology and performance. Morphological analysis identified thinner catalyst layers for spray coating and inhomogeneous PTFE distribution for doctor blade coated GDEs. Electrochemical characterization in the HT-PEM half-cell displays significantly lower performance for ultrasonic spray-coated GDEs, possibly due to more pronounced phosphoric acid penetration. On the contrary, implementation of GDEs as cathodes in the HT-PEMFC yields comparable performances for both coating methods but differences in ORR and proton transport resistances determined by distribution of relaxation times analysis. Moreover, it was shown that inhomogeneous PTFE distribution caused by high amounts of hydrophilic O-/N-functionalities negatively affects HT-PEMFC performance. This study helps to understand the impact of GDE fabrication and Fe–N–C catalyst properties in HT-PEM half- and single-cell application.