Performance of High Temperature Polymer Electrolyte Membrane Fuel Cells as a Function of Polybenzimidazole Membrane Modification

Polymer electrolyte membranes (PEM) of high-temperature PEM fuel cells (HT-PEMFC) are commonly based on phosphoric acid-doped polybenzimidazole (PBI). However, these membranes suffer from acid leaching and limited mechanical stability. In this study, five different PBI membrane modifications, including inorganic fillers (SiC, Si₃N₄, SiO₂), crosslinking, and high-solid content, are explored to increase the solid content of the membranes (up to 18 wt%), which could potentially increase mechanical stability. All modifications are based on the industrial fabrication process of the commercial Celtec-P membrane to enable direct comparison in HT-PEMFC. HT-PEMFC testing reveal comparable performance to the Celtec standard when incorporating SiC particles with lower membrane resistance. Lowest performance is found for crosslinked and high-solid-based membrane electrode assembly (MEA), which is traced back to acid leaching and increased proton transport resistances. The evaluation of performance under operation with reformate reveal no beneficial effect of the membrane modification. This study helps to implement novel HT-PEM candidates in the industrial fabrication process and provides direct comparison to the already commercialized Celtec technology regarding MEA performances and stabilities.