Influence of the Solvent in the Preparation of PGM-Free Cathode Gas Diffusion Electrodes for PEMFC Application

Kurzfassung

Polymer electrolyte membrane fuel cell (PEMFC) technology has become a greener alternative to the combustion of fossil fuel. Platinum (used as catalyst) is one of the most expensive materials used in the manufacturing of PEMFC systems. To reduce the manufacturing cost of PEMFC, platinum group metal (PGM)-free catalysts draw interest in the electrochemical society. The type of solvent and ionomer content utilized to fabricate cathode catalyst layer (CCL) in a PGM-free PEMFC plays an important role in the fuel cell performance. The performance and durability of PGM-free cathode electrodes are still crucial for their wide commercialization. In this study, a catalyst belonging to the family of Fe-N-C materials was mixed with different solvents and ionomer ratios in ink suspensions for cathode electrode fabrication. Their performances were analyzed via membrane electrode assembly (MEA) single cell testing under H2/Air operating conditions, and subsequently subjected to a potentiostatic hold stability test at 400 mV for 48 hours. Ink suspensions were further characterized by zeta-potential measurements. A clear correlation was found between fuel cell performance and ionomer content and type of solvent used. Zeta-potential analysis allowed to comprehend the impact of particle dispersion in the performance of the electrode, in which there seems to exist an “optimal” balance between excessive or insufficient particle dispersion. Stability testing revealed that higher performing MEAs also suffer higher degradation rates, yet the main responsible mechanism remains unknown. For the solvent types and ionomer contents tested in this work, use of methanol at 50 weight percent (wt%) of ionomer content produced the highest peak power density (0.229 W·cm-2), which is comparable to the most recent state of the art PGM-free catalysts.