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In recent times, high-temperature polymer electrolyte membranes (HTPEMs) have emerged as viable alternatives to the Nafion-based low-temperature-operated polymer electrolyte membrane fuel cells. This is owing to their higher tolerance to fuel impurities, efficient water management, and higher cathode kinetics. However, the most efficacious HTPEMs such as poly(benzimidazole) (PBI) or 2,5-poly(benzimidazole) (ABPBI), which rely on the extent of phosphoric acid (PA) doping level for fuel cell performance, suffer from poor mechanical properties at higher acid doping levels and dopant leaching during continuous operation. To overcome these issues, we report the synthesis of ABPBI membranes and fabrication of ABPBI−zirconium pyrophosphate (α-ZrP)-based nanocomposite membranes by an ex situ methodology using methane sulfonic acid as the solvent. The incorporation of hydrophilic α-ZrP into the membrane resulted in higher dopability of PA (6.5 mol) and proton conductivity (46 mS/cm) of the membranes (10 wt % of α-ZrP) as against the corresponding values of 3.6 mol and 27 mS/cm, respectively, for the pristine membrane. More remarkably, these property improvements could be achieved while simultaneously augmenting the thermomechanical properties and oxidative stability of the membranes. The unit-cell tests showed a marked improvement in the maximum power density for the nanocomposite membrane (335 mW/cm 2 at 10 wt % α-ZrP content) over the pristine ABPBI membrane (200 mW/cm 2 ). We also report for the first time the feasibility of a 100 W HTPEM fuel cell (HTPEMFC) stack operated with the nanocomposite membrane with an active area of 39 cm 2 . The HTPEMFC stack delivered a stable voltage and power output, with a voltage drop rate of 0.84 μV/h over a run time of 730 h.

A wide range of solvents have been examined to find their effect on radiation-induced grafting of 4-vinyl pyridine onto fluorinated ethylene propylene copolymer by simultaneous irradiation technique. The effect of solvent on percentage of grafting has been monitored by varying monomer concentration and total dose of radiation. Further grafting results have been correlated with the solubility parameter of the solvent and solvent mixtures. Evidence of grafting has been based on characterization of grafted samples in terms of FTIR, EDAX, X-ray mapping, thermogravimetric analysis, and dynamic mechanical analysis. Depth profiling of a few representative grafted films were studied by viewing the cross-sectional distribution of elemental nitrogen using SEM-EDAX. The results suggest that with increase in grafting the grafting front propagates from the surface toward bulk, thus establishing the frontal mechanism of radiation grafting. Furthermore, the grafted films were characterized for their surface properties using contact angle goniometry.