Preparation And Properties Of Filling-composite Proton Exchange Membranes

At present,energy shortage and ecological environment problems have been attracted much more attention.Fuel cell showed advantages of high operating efficiency and zero emissions of pollutants,which is one of the preferred source of clean energy in the 21^stt century.The perfluorinated sulfonic acid proton exchange membranes displayed both high methanol permeability and cost.Therefore,Sulfonated poly?arylene ether sulfone?and polyethersulfone?SPAES/PES?were selected as the basic polymers in this work.In this work,a series of three membranes were successively prepared?SPAES/PES and both SPAES/PES and SPAES/PES-TiO₂ filled with SPAES-50?and at the same time,their properties were compared.From the experimental results,SPAES/PES microporous membranes showed the better thermal and dimensional stability as well as the microporous membranes exhibited high conductivity levels under low IEC.The S30-40?IEC=0.39 mmol/g?as an example of microporous membrane reached at 16.0 mS/cm and 32.1 mS/cm at 30? or 90?,respectively.The rate of weight loss from all membranes were less than 0.2%after treatment with Fenton reagent at high temperature?3%H₂O₂,2mg/L FeSO₄,80?,1h?and the rate of methanol permeability were relatively low(1.22×10^-6 cm²/s),however,the magnitude of methanol permeability of all 30%series microporous membranes were lower than that of Nafion membrane.The composite membranes showed good hydrolytic stability.The rate of weight loss of S30-40 membrane was 1.7%after the treatment with hot water?140??.Out of that,the microporous membranes exhibited good resistance towards hydrolytic and oxidation stability,and then act as suitable precursor for filling and modification.Using vacuum filtration SPAES50-DMF/aqueous solution?2/1?to fill the microporous membranes,after filling the microporous membranes with SPAES-50 solution,the filled membranes showed excellent hydrolytic and oxidation stabilities,maintained high mechanical and chemical stabilities,low methanol permeability,higher IEC and proton conductivity compared to non-filled membranes.The filled membrane?S30-40+F50?showed the best performance such as membrane conductivity became 50.4 mS/cm at 90? and IEC was 0.69 mmol/g.The rate of weight loss was 8.2%after hot water?140??treatment for 24 h and conductivity was maintained at level of 91%.The rate of weight loss was 0.66%after treatment into Fenton reagent?3%H₂O₂,20 mg/L FeSO₄,80?,1h?.In addition,methanol permeability was 6.8×10^-8 cm²/s,which was lower than that of Nafion112.The TiO₂ were doped into the most excellent microporous membrane matrix?S30-40?and filled with SPAES-50,which further improved the comprehensive performance of this composite membrane.The proton conductivity of 2wt%TiO₂ doped membrane reached71.7 mS/cm and 97.7 mS/cm at 30? and 90?,respectively.When doping amount was2.5wt%,the methanol permeability reduced to 1.51x10^-8 cm²/s,which reduced the fuel gas leakage during fuel cell operation.In addition,composite membranes showed higher conductivity and low permeability,continued excellent oxidation and hydrolytic stabilities,which indicated a greater improvement compared with the previous works.Filling microporous membranes can effectively improve the physical and chemical properties of sulfonated aromatic electrolyte membranes as well as excellent durability,long operating conditions.The furthermore optimizations for this work are expected to improve the properties of these microporous membranes for wide use in fuel cells.