侧链型磺化聚芳醚酮/磺化聚乙烯醇复合型直接甲醇燃料电池用质子交换膜

Sulfonated Poly(aryl ether ketone) on Side Chain/Sulfonated Poly(vinyl alcohol) Composite Proton Exchange Membrane for Direct Methanol Fuel Cells

通过溶液共混法制备了不同磺化聚乙烯醇(SPVA)含量的侧链型磺化聚芳醚酮/磺化聚乙烯醇(S-SPAEK/SPVA)复合膜.应用红外光谱(FTIR)对复合膜进行了表征,扫描电镜(SEM)显示SPVA均匀分布在复合膜中.通过对复合膜的性能测试发现该系列复合膜具有良好的热性能、较高的吸水率和保水能力.SPVA中的羟基能有效地阻碍甲醇的透过,甲醇渗透系数从S-SPAEK/SPVA5复合膜的7.9×10-7cm2·s-1降低到S-SPAEK/SPVA30的1.3×10-7cm2·s-1,比S-SPAEK膜的11.5×10-7cm2·s-1降低了一个数量级.SPVA的引入增加了亲水基团数量,增加了复合膜的吸水和保水能力,有利于质子按照"Vehicle"机理和"Grotthuss"机理进行传递,柔软的SPVA链段与S-SPAEK侧链聚集成亲水相区,形成连续的质子传输通道,提高了复合膜的质子传导率.在25和80℃时,S-SPAEK/SPVA30复合膜的质子传导率分别达到了0.071和0.095S·cm-1.可见,S-SPAEK/SPVA复合膜有望在直接甲醇燃料电池中得到应用.

Poly（aryl ether ketone）/sulfated poly（vinyl alcohol） （S-SPAEK/SPVA） composite membranes with different mass fractions of SPVA were prepared by solution casting using highly sulfonated side-chain- type sulfonated poly（aryl ether ketone） and sulfated poly（vinyl alcohol） as raw materials. Fourier transform infrared （FTIR） spectroscopy confirmed the structure of the S-SPAEK/SPVA composite membranes. Scanning electron microscope （SEM） images showed that SPVA was uniformly dispersed in an S-SPAEK polymer matrix. The uptake and swelling behavior, water retention capacity, methanol permeability, and proton conductivity of the composite membrane were investigated systematically. The performance testing of the composite membranes revealed that thermal stability and water absorption and retention capabilities were improved by introduction of SPVA. The methanol permeability of S-SPAEK/SPVA composite membranes decreased as the content of SPVA increased because the hydroxyl groups could effectively obstruct diffusion of methanol molecules. The methanol diffusion coefficients of the composite membranes decreased from 7.9 × 10-7 cm2 · s-1 for S-SPAEK/SPVA5 to 1.3 × 10-7 cm2 · s-1 for S-SPAEK/SPVA30; considerably lower than 11.5× 10^-7 cm^2×· s-1 for the pure S-SPAEK membrane. The water absorption and retention capabilities increased as the numbers of hydrophilic groups increased by introduction of SPVA. As a result, the proton conductivity of the composite membranes increased with increasing water absorption and retention capabilities according to the Vehicle and Grotthuss mechanisms. The flexible chain segment of SPVA interacted strongly with the pendant chain of S-SPAEK, aiding hydrophilic/ hydrophobic separation, and improving the proton conductivity of the composite membranes. The proton conductivity of the S-SPAEK/SPVA30 composite membrane reached 0.071 and 0.095 S.cm^-1 at 25 and 80 ℃ , respectively. These results show that S-SPAEK/SPVA composite membranes are promising for application in direct methanol fuel cells.