Study On The Preparation And Application Of Sulfonated Poly(ether Ether Ketone)s/ionic Liquids Composite Membrane

The proton exchange membrane is one of key sections of the proton exchange membrane fuel cell.Nafion membranes possesses the advantages of high proton conductivity,good chemical stability,however its swelling phenomenon is serious when there is much water and it is difficult to make,cost high;the proton conductivity is extremely low at high temperature?>373K?,this limits the operation temperature of fuel cell critically.High temperature proton exchange membrane fuel cell?HT-PEMFC?has become a hot research topic in the field of fuel cell because of its simple water and heat management and strong anti CO ability.Sulfonated poly?ether ether ketone??SPEEK?has better proton conduct ability,low cost and better stability at high temperature,therefore it is the most possible non-fluorine polymers to substitute for Nafion.This paper adopts two ways mostly to modify SPEEK membrane: one is incorporating with non-aqueous proton conductor tertiary ammonium ionic liquid?AIL?;another is incorporating with hygroscopic inorganic oxide Si O2.The research has important application value for the development of new proton exchange membrane.SPEEK membranes were prepared using direct sulfonation method,and the sulfonation degree of SPEEK membrane was determined by H NMR.SPEEK was characterized by Fourier transform infrared?FTIR?spectroscopy and thermo gravimetric analysis?TGA?.It is concluded that thermal stability of SPEEK sample is better.The effect of reaction time and temperature on the sulfonation degree was studied.It is foundthat the sulfonation degree increases first and then stabilizes,with the increase of time or temperature.The proton conductivity is obtained by three electrode system electrochemical impedance spectroscopy.The proton conductivity of SPEEK75 membrane whose sulfonation degree is 75% is the highest at 13.18 mS/cm at 393 K.The triethyl ammonium dihydrogen phosphate?[?CH3CH2?3NH+] [H2PO4-],TEAP?and triethyl ammonium hydrogen sulfate?[?CH3CH2?3NH+] [HSO4-],TEAS?were prepared by neutralization method and characterized by Fourier Transform infrared?FTIR?spectroscopy and H NMR.Then SPEEK/TEAS and SPEEK/TEAP composite membranes were prepared by solution casting method.It is observed that there are irregular shapes' crystals distribution even on SPEEK/IL composite membrane surface and net structure in the cross-section of SPEEK/IL membranes by scanning electron microscope?SEM?.The thermal stability and flexibility are better.SPEEK/IL membranes have no obvious two-phase separation,and their glass transition temperatures are above 400 K.The proton conductivity of SPEEK75-35 S membrane which is that the sulfonation degree of SPEEK is 75% then incorporate 35% TEAS into SPEEK is the highest to 6.936 mS/cm at 393 K.SPEEK96-50 P membrane which is that the sulfonation degree of SPEEK is 96% then incorporate 50% TEAP into SPEEK is 7.896 m S/cm.The ionic liquids loss rate in the membrane mainly concentrates in the first hour,and the IL loss rate is among 30%⁵0%.The compatibility of TEAS or TEAP ionic liquids with Pt/C catalysts is good from the CV curve.The open-circuit voltage of single fuel cells with prepared SPEEK/IL composite membranes is high.The open-circuit voltage of SPEEK/IL composite membrane approaches to 0.8V roughly.The polarize curve of fuel cell with the SPEEK75-35 S,SPEEK96-15 S,SPEEK96-35 P composite membrane is better than that with the Nafion212 membrane obviously.SPEEK/TEAS/SiO₂ and SPEEK/TEAP/SiO₂ composite membranes were prepared by solution casting method.It is observed that there are a little cracks and pits on the composite membrane surfaces,and three-decker structure with filling in cross section by scanning electron microscope?SEM?.Ion exchange capacity indicates that membranes absorb some water due to the addition of SiO₂.The ternary component membranes were characterized by Fourier transform infrared?FTIR?spectroscopy and thermo gravimetric analysis?TGA?.It is concluded that thermal stability of these samples decreases.However the ionic liquids loss rate in these membranes decreases and proton conductivity increases.the IL loss rate of SPEEK/IL/SiO₂ composite membranes is among 30% 50%.The proton conductivity of SPEEK60-35 S 13%SiO₂ composite membrane increases compare to SPEEK60-35 S membrane and is high to 5.595 mS/cm at298 K.The electrochemical performance of SPEEK60-35 S 13%SiO₂ membrane is the best and its open voltage is 0.987 V from the polarization curve.