| Fuel cells have attracted much attention due to their high energy conversion efficiency and low pollution.Proton exchange membrane is one of the most important components in proton exchange membrane fuel cells.In order to break"trade-off"balance between"IEC-water absorption-ionic conductivity-physicochemical stability"in the development of proton exchange membrane(PEM)via dip-coating method,we prepared a series of filling type composite membranes.The commercial poly tetra fluoroethylene(PTFE)porous membrane was used as the matrix,high ion exchange capacity(IEC)sulfonated poly(ether ether ketone)or sulfonated poly(arylene ether sulfone)was used as the filler,and low IEC sulfonated poly(arylene ether sulfone)was used as the surface coating material.Compared with the traditional perfluorosulfonic acid membrane,the pore-filling proton exchange membrane has the advantages of non-swelling,low methanol permeability,high proton conductivity,low price and wide range of materials.The relationship between dip-coating conditions and membrane properties was studied.When SPEEK73(sulfonation degree=73%,IEC=2.11 mmol g-1)was used as the filler,the more times of the SPEEK73 was impregnated,the higher the IEC and proton conductivity of the membrane,but the higher the swelling;the more times of the SPAES40(sulfonation degree=40%,IEC=1.72 mmol g-1)was coated,the lower the IEC,proton conductivity and swelling.The conductivity of M0.45-113K(2)impregnated with SPEEK73 for 5 times and coated with SPAES40 twice in water at 80?was 37.2 m S·cm-1,an acceptable conductivity level.The swelling rate of the surface and the thickness swelling rate at 80?were only 1.4%and 8.7%,respectively.The surface coating of SPAES40 improved the hydrolysis stability of the pore-filling membrane.After 24 hours of hydrolysis treatment at 120?,the proton conductivity loss rate of SPEEK-filled membrane without coating reached 100%at 80?,reduced to 62.2%for one-time SPAES40 coating,and significantly reduced to 5.4%after for twice SPAES40 coating.The relationship between the pore size of the substrates and the performance of the membranes was studied.The larger the pore size of PTFE substrate impregnated with SPEEK73 for six times and coated with SPAES40 twice,the higher the IEC and proton conductivity,but the swelling increased and the hydrolysis stability decreased.Among them,the IEC of M0.45-114K(2)(with pore size of 0.45?m,six times of SPEEK73immersion and twice SPAES40 surface coating)was 0.86 mmol g-1.The proton conductivity at 80?reached 37.5 m S·cm-1,the thickness swelling rate was 12.6%,and the area swelling rate was 1.7%.After hydrolysis treatment at 120?and 24 h,the loss of proton conductivity was 62.7%.Under the same conditions of dip-coating procedure and pore size,the filler was replaced by SPAES50(sulfonation degree=50%,IEC=2.08 mmol g-1)to prepare the pore-filling membrane.The larger the pore size of PTFE substrate,the higher the IEC and proton conductivity,and the higher the membrane swelling.However,after high temperature hydrolysis treatment,the proton conductivity increased due to smoother proton channel and blending of surface coating and filler.The IEC of M0.45-114S(2)(with pore size 0.45?m,six times of SPAES50 dipping,twice SPAES40 surface coating)was0.80 mmol·g-1,At 80?,the proton conductivity was 65.3 m S·cm-1,the thickness swelling rate was 16.4%,and the area swelling rate was 2.5%.After 24 hours of hydrolysis treatment at 120?,the proton conductivity increased by 69.7%at 30?.The IEC,water absorption and swelling levels were similar to membranes filled with SPEEK73,but the conductivity and hydrolysis stability were better.In conclusion,under the same conditions of filler IEC,substrate,filling procedure and pore size,SPAES pore-filling membrane is better than SPEEK pore-filling membrane. |
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