Composite Poly(Aryl Ether Ketone)Proton Exchange Membranes:Synthesis And Property Studies

Proton exchange membrane fuel cells(PEMFCs)have attracted attention for their promising applications in clean energy service such as portable devices and stationary supply.Compared with conventional power generation systems,PEMFCs work without any combustion of fossil fuels and emission zero pollutants.As the core component,polymer electrolyte membrane(PEM)acts as an electrolyte to transport protons from anode to cathode.The commercially available PEMs for PEMFCs(e.g,Nafion)still have some problems such as high cost,high fuel crossover,and low conductivity at high temperatures with low humidity.Thus,we developed two kinds of novel composite membranes to conquer above questions.The sulfonated poly(arylene ether)s(SPAEs)series PEM materials have some special properties compared to the state-of-the-art Nafion,such as lower fuel crossover,better thermal stabilities and mechanical properties,comparable proton conductivity and,especially,lower cost.In this paper,organic-inorganic composite membranes based on sulfonated poly(arylene ether ketone sulfone)have been prepared.The filler1-ethyl-3-methyl imidazolium phosphotungstate(PWA-IL)have been prepared successfully through molecular modification of phosphotungstic acid(PWA)with ionic liquid(IL).The obtained PWA-IL is introduced into SPAEKS matrix aiming to enhance the proton conductivity and decelerate the leakage of ionic liquid.After a series of tests,it is found that PWA-IL causes higher proton conductivity and protects IL from losing by hydrogen bonding.In particular,the obtained SPAEKS-80/PWA-IL membrane shows excellent long-term stability with 98.4% of PWA-IL residue after 132 h in water.Simultaneously,the PWA-IL plays a positive role in improving methanol resistance.SPAEKS-80/PWA-IL membrane exhibits good proton conductivity(0.127 S cm-1)under fully hydrated conditions at 80 °C.Based on the previous research,we found that the introduction of imidazole group contributes to proton conductivity.Imidazole as basic group is a nitrogen heterocyclic which can easily form acid-base pairs with acids.Protons would jump from acid group to base group directly by Grotthuss mechanism.To research the influence of different nitrogen heterocyclic on the properties of membranes,a series of nitrogen heterocyclic functional polymer membranes were successfully prepared for high temperature proton exchange membranes.Poly(arylene ether ketone)(PAEK)is prepared as the polymer backbone.A certain level bromine methyl degree BrPAEK was obtained by bromination with NBS as brominated reagents.By the reaction between bromine methyl and nitrogenheterocyclic,Pyridine(Pd),1-Methylimidazole(MeIm),1H-Benzotriazole(BTA)and3-Amino-1,2,4-triazole(AmTr)are introduced into BrPAEK.Those four types of membranes show different PA adsorption ability and proton conductivity.Results indicate that MeIm modified membranes adsorb relatively more PA due to its more stretch structure.Proton conductivity tests show that BrPAEK-MeIm membranes possess the highest proton conductivity.Such as BrPAEK-MeIm1.3 exhibits good proton conductivity(0.091 S cm-1)under hydrophobic conditions at 170 oC.At the same time,thermal stability,oxidation stability and mechanical properties are good enough to be used as PEMs.