High temperature polybenzimidazole membrane electrode assemblies using pyridine-polybenzimizazole as catalyst layer binder

We synthesize four pyridine-polybenzimidazoles (PyPBIs) and one polybenzimidazole (PBI) from a tetramin monomer (i.e., 3,3 '-diamino benzidine (DABZ)) and two dicarboxylic acid monomers (i.e., isophthalic acid (IPA) and 2,6-pyridinedicarboxylic acid (PyA)) with PyA/IPA molar ratios of 6/4 (i.e., PyPBI-64), 5/5 (i.e., PyPBI-55), 4/6 (i.e., PyPBI-46), 3/7 (i.e., PyPBI-37), and 0/1 (i.e., PBI-11). The PyPBIs and FBI with molecular weight of similar to 1.0-1.3 Chi 10(-4) g mol(-1) are used as Pt-C (Pt on carbon support) binders for fabricating gas diffusion electrodes (GDEs) and are doped with H3PO4 to prepare membrane electrode assemblies (MEAs). We demonstrate that both the H3PO4 loading of the GDE and the fuel cell performance of the MEA at 160 degrees C with unhumidified H-2/O-2 fuel increase with the increase of PyA monomer content of the PyPBI (or PBI) binder in the GDEs according to the sequence of PBI-11 < PyPBI-37 < PyPBI-46 < PyPBI-55 < PyPBI-64. The higher PyA content PyPBI provides more binding sites for H3PO4 in GDE and enhances fuel cell performance. (C) 2014 Elsevier B.V. All rights reserved.