As the world’s transportation is seeking to switch towards renewable and sustainable sources of energy, the research in fuel cell technology has gained momentum. Proton exchange membrane fuel cell (PEMFC) operating at temperature range 100–200°C (high-temperature proton exchange membrane fuel cells, HT-PEMFCs) has gained interest in their major application to electric power generation. The most promising material is polybenzimidazoles (PBI). Synthesis methods such as condensation polymerization, solid-state or melt polymerization, etc. give the polymer with different inherent viscosity. The monomer modifications both in tetramine and the diacid, reveal variations in glass transition value. Further insight into the membrane casting solvents and methods along with its proton conductivity has been reviewed. Review paper is comprising of Part 1: for the synthesis methods, structural changes, and applications of PBIs in HT-PEMFCs while, Part 2: for the various kinds of PBIs has been discussed.[Formula: see text]

A series of polybenzimidazoles (PBIs) incorporated main chain 4-pyridine bridge groups were synthesized from 4,4′-([4,4′-bipyridine]-2,6,-diyl)bis (benzene-1,2-diamine) which reacted with four different diacids like isophthalic acid,4,4′-Oxibis benzoic acid, 5-amino isophthalic acid and 2,5-pyridine dicarboxylic acid using polyphosphoric acid as solvent. A process termed dispersion polymerizationhas been developed to prepare PBIs.For the membranepreparation, 4-pyridine-bridge polybenzimidazole (Py-PBI) productswere re-dissolved in dimethyl sulfoxide and cast. The polymer structure characterization included FT-IR, UV, Powder XRD, Water Uptake, Swelling Ratio, Ion exchange capacity, Acid doping, Acid leaching, Oxidative stability, and Polymer inherent viscosity find out by using Ubbelohde viscometer whilethermal stability assessments via thermogravimetric analysis. The Py-PBI-based polymer electrolyte membranes’ mechanical properties measurement showed that the 4-pyridine-bridge PBIs membranes were flexible, thermally stable, and mechanically strong when compared with conventional PBI. The current-voltage (I-V) characteristics of the 4-Py-PBI membrane show that the conductivity of the 4441P membrane is 0.546 S cm−1.