Preparation And Characterization Of Modified Polyepichlorohydrin/Polytetra Fluoroethylene Composite Anion Exchange Membrane

Alkaline anion exchange membrane fuel cell (AAEMFCs) is an alkaline fuel cellwhich uses the anion exchange membrane as the electrolyte. Compared withtraditional proton exchange membrane fuel cell, AAEMFCs, as a new member of thefamily of fuel cell, have many merits, including the low methanol permeability,simple water management, small fuel oxidation activation energy and availablenon-noble metal catalyst. As a core block of the AAEMFCs, anion exchangemembranes (AEMs) play a dual role of electrolyte and diaphragm. Its performancedirectly affects the efficiency and life time of fuel cell and. However, manyweaknesses are existed at present, such as the complex preparation method, seriouspollution, and poor mechanical performance and stability. Therefore, in this paper, weprepared the new polyepichlorolydrin (PECH)/polytetrafluoroethylene (PTFE) anionexchange composite membrane with outstanding performance, and the structure andperformance of the membrane were studied systematically.Firstly, polyepichlorohydrin (PECH) was crosslinked with diethylamine,quaternized with1-methylimidazole, and combined with polytetrafluoroethylene(PTFE) membrane to form composite anion exchange membrane of Cl typecrosslinked quaternized PECH/PTFE (Cl-CQPECH/PTFE). Then, after the membranewas exchanged by alkali, the HO type HO-CQPECH/PTFE composite anion exchangemembrane was obtained. The result showed that HO-CQPECH/PTFE exhibited notonly high ionic exchange capacity and ionic conductivity, but also high tensilestrength, good chemical stability and outstanding thermal stability.Secondly, PECH was crosslinked with2-methylimidazole and combined withpolytetrafluoroethylene (PTFE) membrane to form crosslinked PECH/PTFE(CPECH/PTFE). Then, CPECH/PTFE was quaternized by1-methylimidazole toobtain Cl type crosslinked quaternized PECH/PTFE (Cl-CQPECH/PTFE). Then, afterthe membrane was exchanged by alkali, the HO type HO-CQPECH/PTFE compositeanion exchange membrane was obtained. The results showed that the use of 2-methylimidazole as the crosslink agent could avoid the solubility of the compositemembrane in water and DMSO. With the increase of2-methylimidazole, the solubilityof PECH ionomer was decreased. M-3, one of the CQPECH/PTFE membrane, hadinitial decomposition temperature of250°C and tensile strength of67.3Mpa.Moreover, the water uptake and swelling degree were45.3%and9.01%at30°C,respectively; conductivity was0.027S/cm at80°C. A good long-term stability wasalso observed (there was no decrease of the conductivity in1M KOH solution at60°C for15days). A single H2/O2fuel cell test using the M-3at50°C indicated a peakpower density of23mW/cm2. Its excellent comprehensive performance suggested itwas expected to get a wide range of applications in alkaline anion exchangemembrane fuel cell.Finally, excessive2-methyl imidazole was reacted with epichlorohydrin. Then,moderate amount of1,4-dibromobutane was added, and the composite was combinedwith the PTFE membrane to form Br type crosslinked quaternized PECH/PTFE(Br-CQPECH/PTFE). Then, after the membrane was exchanged by alkali, the HOtype HO-CQPECH/PTFE composite anion exchange membrane was obtained. Theresult showed that the as-prepared M-5composite membrane had initialdecomposition temperature of250°C. The water uptake and swelling degree were72.31%and6.40%at30°C, respectively; conductivity was0.0342S/cm at80°C.Besides, there was weak change of the conductivity in1M KOH solution at60°C for15days, showing good comprehensive performance.