Enhancement of Proton Conductivity Performance in High Temperature Polymer Electrolyte Membrane, Processed the Adding of Pyridobismidazole

Abstract

A pyridobisimidazole unit was introduced into a polymer backbone to obtain an increased doping level, a high number of interacting sites with phosphoric acid and simple processibility. The acid uptake of poly(pyridobisimidazole) (PPI) membrane could reach more than 550% (ADL = 22), resulting in high conductivity (0.23 S·cm−1 at 180 °C). Along with 550% acid uptake, the membrane strength still held 10 MPa, meeting the requirement of Proton Exchange Membrane (PEM). In the Fenton Test, the PPI membrane only lost around 7% weight after 156 h, demonstrating excellent oxidative stability. Besides, PPI possessed thermal stability with decomposition temperature at 570 °C and mechanical stability with a glass transition temperature of 330 °C.

Nitrogen Dense Distributions of Imidazole Grafted Dipyridyl Polybenzimidazole for a High Temperature Proton Exchange Membrane

“…In order to avoid the trade-off between conductivity and mechanical strength, many efforts have been made, such as crosslinking [11,12], nano filler composition [13][14][15], and basic groups' introduction in the PBI main chain or side chain [16][17][18][19]. During these methods, the introduction of basic groups such as pyridine, imidazole, and triazole in the PBI can increase the number of proton hopping sites along the PBI main chain; therefore, the proton conductivity can reach a high level even when the PA ADL is low, and the low ADL can maintain a good strength of the PBI membrane without excessive swelling.…”