Proton exchange membranes prepared by radiation grafting of n-vinyl imidazole/4-vinyl pyridine onto poly (ethylene-co-tetrafluoroethylene) for high-temperature PEM fuel cells
Rajabalizadeh Mojarrad, Naeimeh (2018) Proton exchange membranes prepared by radiation grafting of n-vinyl imidazole/4-vinyl pyridine onto poly (ethylene-co-tetrafluoroethylene) for high-temperature PEM fuel cells. [Thesis]
The large contribution of fossil fuels emission to environmental pollution, as well as limited supplies, reveal the importance of alternative power sources. In this regard, fuel cells can be considered one the most favorable options for diverse applications. However, developing materials with properties that meet the requirements of fuel cell systems with high performance, reliable lifetimes and cost-effectiveness is still a challenging issue. Improvement of the membrane as the heart of the fuel cell is one of the growing research areas. Radiation-induced grafting methods have attracted extensive attention as a simple method for scaling up. The suitability of this method in terms of utilizing various combinations of base polymers and monomers results in the production of membranes with desired properties for numerous applications such as high-temperature PEM fuel cells. In this study, 1-vinylimidazole (1-VIm) and 4-vinylpyridine (4VP) monomers have been utilized as monomers to graft onto ɣ-irradiated ethylene-co-tetrafluoroethylene (ETFE) films as the base polymer. Grafting reactions took place at 60°C for 24 h. The radiation grafted copolymer was subsequently doped with phosphoric acid to prepare new membranes for high-temperature operation. The effect of adding ferrous salt as an additive, utilizing various solvents during grafting and changing the monomer ratio on the grafting parameters was investigated. Properties of the resultant membranes were characterized via ex-situ ionic conductivity measurement at varying temperature and humidity, thermal gravimetric analysis (TGA), and mechanical testing was completed using a universal test machine. The fuel cell performance measurements were conducted for the most promising membranes at various relative humidity and temperatures conditions. Additionally, the membranes with an ionic conductivity of 237 mS.cm-1, prepared in the presence of salt with 36% GL at 110°C with 60% RH, exhibit the potential as promising membranes for high-temperature PEM fuel cell.
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