(Invited) Development and Characterization of Electrodes and Membrane Electrode Assemblies for High Temperature PEM Fuel Cells
Authors: Schonvogel Dana , Müller-Hülstede Julia , Zierdt Tanja , Buschermöhle Julia , Schmies Henrike , Uhlig Lisa Maria , Pilinski Nadine , Wagner Peter 
Published: December 2024

Polymer electrolyte membrane fuel cells (PEMFCs) allow the conversion of hydrogen into electrical energy in several fields of portable, mobile and stationary application. The high temperature (HT-) PEMFC type is characterized by a simplified cell design and provides fuel flexibility because of increased catalyst tolerance towards impurities and thus the direct use of industrial quality hydrogen or reformates from various regenerative fuels. Moreover, the increased operating temperature of around 160–180 °C is highly attractive for special fields of application like FC powertrains in aircrafts. Currently, the used gas diffusion electrodes (GDEs), mostly based on Pt catalysts, strongly dominate the production costs of HT-PEMFC systems, since common membrane electrode assemblies (MEAs) exhibit a Pt loading of up to 2 mgPt cm-2.1,2 Also, further electrode and membrane development is required to increase the HT-PEMFC lifetime and to make the system performance competitive with low temperature PEMFC.
This invited talk gives insights into the recent studies of DLR towards catalyst, GDE and membrane optimization for the HT-PEMFC to drastically reduce or completely avoid Pt contents and thereby minimize the electrode costs and to increase long-term stabilities of the materials in the presence of corrosive HT-PEM conditions (conc. H3PO4).2-7 Development strategies with various material and cell characterization methods of the DLR group is presented and supplemented by other studies to give a comprehensive overview on recent HT-PEMFC developments. To reduce or completely avoid Pt contents, metal-nitrogen-carbons (M-N-Cs) are synthesized and tested in phosphoric acid towards the oxygen reduction reaction (ORR) using rotating disc electrodes (RDEs), and are furthermore used as supports for low Pt contents.7

Besides catalyst studies towards activity, selectivity and stability in a three-electrode setup using RDEs on the one hand and using GDEs on the other hand, novel catalysts and membranes are implemented into HT-PEM single cells to perform fuel cell tests under harsh cycling conditions. Physical, chemical and imaging analytics (µ-computed tomography, TEM, XPS, ...) reveal material degradation after testing. Figure 1 shows an example of a new MEA type based on a phosphoric acid doped polybenzimidazole membrane (PBI) with SiC inorganic filler and the standard MEA without filler. The single cell measurements show increased initial performance and reduced degradation after 1,000 h of load cycling (1.0 and 0.6 A cm-2), but also show increased hydrogen crossover due to SiC.6

REFERENCES
[1] N. Seselj, et al., Adv.
Materials
2023, 35, 40, 2302207.
[2] J. Müller-Hülstede, L. M. Uhlig, H. Schmies, et al., ChemSusChem
2023, e202202046.
[3] H. Schmies, T. Zierdt, J. Müller-Hülstede, et al., J. Power Sources
2022, 529, 231276
[4] H. Schmies, N. Bengen, J. Müller-Hülstede, et al., Catalysts
2023, 13, 343.
[5] J. Müller-Hülstede, H. Schmies, D. Schonvogel, et al., International
Journal of Hydrogen Energy
2023, in press.
[6] D. Schonvogel, J. Belack, J. Vidakovic, et al., Journal of Power Sources
2024, 591, 233835.
[7] D. Schonvogel, N.K. Nagappan, J. Müller-Hülstede, et al., Journal of Electrochemical Society
2023, 170, 114518.

Figure 1