Preparation And Properties Of Hybrid Anion Exchange Membranes For Fuel Cell Applications

At present,environmental pollution and energy shortages are seriously plaguing the survival and development of human beings.As a clean and efficient new energy source,fuel cells have attracted more and more attention.Due to rapid reaction kinetics,low cost,and wide range of fuel choices,anion exchange membrane fuel cells have become important issues,and anion exchange membranes play an important role as the key components of fuel cells.Doping is one of the most important methods to improve the performance of anion exchange membranes(AEMs)for fuel cell.In this dissertation,the quaternized poly(aryl ether ketone)was prepared by nucleophilic polycondensation reaction,Friedel-Crafts reaction and menshutkin reaction.Modified titanium dioxide nanotubes(QTNT)and exfoliated carbon nitride(C3N4)were dope into the polymer respectively,then the hybrid anion exchange membranes were prepared by solution casting method and the performance for fuel cell was studied.Firstly,the effects of the doped QTNT on the performance of AEMs were studied.QTNT was prepared by grafting γ-chloropropyltrimethoxysilane on the surface and quaternized by TMA,the ion exchange capacity(IEC)of the obtained QTNT was 1.16 mmol/g,then QTNT was doped into the quaternized poly(aryl ether ketone)to prepare hybrid membranes.The IEC of obtained membranes was in the range of 1.52 to 1.59 mmol/g,compared with the pure membrane,QPAEK-x-QTNT membranes exhibited enhanced solvent resistance and suppressed water swelling,as well as improved hydrolytic stability and chemical stability towards alkali solution.QPAEK-1%-QTNT showed higher water uptake and ionic conductivity than QPAEK and QPAEK-1%-TNT membranes.In summary,QPAEK-1%-QTNT membrane exhibited the best comprehensive performance with water uptake of 36.5%and ion conductivity of 37.9 mS/cm at 60 ℃,and after treated by 1 mol/L NaOH solution at 60 ℃ for 240 h,the ion conductivity maintained 66%of the initial value.Then the effect of exfoliated carbon nitride on the performance of AEMs was studied.C3N4 was successfully prepared from graphite carbon nitride by acid chemical exfoliating of concentrated sulfuric,and the particle size was about 1 μm,then the obtained C3N4 was doped into quaternized poly(aryl ether ketone)to prepared hybrid membranes and the properties were investigated.The IEC of the obtained membranes was in the range of 1.29 and 1.33 mmol/g,compared with the pure membrane(QPAEK2),QPAEK2-y-C3N4 membranes showed enhanced rigidity and stabilities,as well as improved water uptake and ionic conductivity with low amount of C3N4.Overall,QPAEK2-0.5%-C3N4 membrane exihibit the best performance with conductivity of 25 mS/cm at 60 ℃,great mechanical properties and dimensional stability.When QPAEK2-0.5%-C3N4 was treated with 1 mol/L NaOH solution at 60 ℃ for 240 h,ionic conductivity could still maintain 89%of the initial value,which showed satisfactory alkaline stability.In summary,doping proper amount of QTNT or C3N4 could improve the performance of AEMs,the prepared membranes would be promising for the potential application in anion exchange membrane fuel cells and beneficial to the development of environmentally friendly energy.