Thermally crosslinked and quaternized polybenzimidazole ionomer binders for solid alkaline fuel cells

Abstract

A novel anion-conducting ionomer binder, quaternized polybenzimidazoles (QPBIs) with 4-methyl-4-glycidylmorpholin-4-ium chloride (MGMC) in the main-chain and/or in the side group were synthesized for solid alkaline fuel cells (SAFCs). Crosslinking of the poly-benzimidazole derivatives using a crosslinker containing epoxy groups formed ionomer binder in electrodes, and the crosslinked QPBIs showed better mechanical stability than non-crosslinked QPBIs. During the electrode drying process, on-site crosslinking was introduced to form thermally crosslinked ionomer binder in catalyst layers. A bench-scale SAFC with the crosslinked QPBI (CQPBI) containing 35 wt% of ionomer binder showed higher peak power density (35.3 mW cm(-2)) than the SAFC with 2,2'(m-phenylene)-5,5'bibenzimidazole (m-PBI) with 35 wt% of ionomer binder (20.9 mW cm(-2)). The membrane-electrode assembly (MEA) with CQPBI (35 wt% binder) showed two times higher chemical stability than that with m-PBI (35 wt% of ionomer binder) in load cell tests. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.