Constructing High-Density Hydrogen Bonding Networks Via Introducing the Bipyridine Group for High-Performance Fuel Cell Proton Exchange Membranes

Abstract

Constructing high-density hydrogen bonding networks is crucial to improve the proton conductivity of proton exchange membranes (PEMs) and the single-cell output power of high-temperature fuel cells (HTFCs). In this work, a series of benzimidazole polymers containing pyridine group in the backbone are successfully synthesized via copolymerization. The high-density hydrogen network is constructed via blending the polyether polybenzimidazole (OPBI) with the bipyridine polybenzimidazole copolymer, and the 1,3,5-triglycidyl isocyanurate that contains nitrogen atoms and hydroxyl groups is used as a crosslinking agent. As a result, the proton conductivity and the output power density of the single cell are significantly enhanced by the high-density hydrogen bonding network. The single-cell performance of 693 mW cm -2 is achieved in the crosslinked OPBI/copolymer blend membranes containing pyridine group under a saturated phosphoric acid (PA) adsorption (284%). Even under the low PA uptake (178%), the proton conductivity (0.050 S cm −1 ) is 2.1 times that of the OPBI membrane (0.024 S cm −1 ), and the output power density of the single-cell performance (501 mW cm −2 ) is 1.4 times that of the OPBI membrane (358 mW cm −2 ). Moreover, the crosslinked membranes also exhibit excellent mechanical properties and dimensional stability. The results demonstrate that introducing a large amount of nitrogen sites into polybenzimidazole crosslinked membranes is an effective strategy for preparing high-performance fuel cell PEMs.

Keywords: hydrogen bonding network, high-temperature proton exchange membrane fuel cells, bipyridine polybenzimidazole, proton exchange membranes, crosslink