磺化双酚芴型聚醚醚酮质子交换膜的制备及其在钒流电池中的应用

以双酚芴为结构单元合成双酚型聚醚醚酮聚合物,聚醚醚酮经浓硫酸磺化在双酚芴结构单元中引入磺化基团制备出聚醚醚酮质子交换膜(SF-PEEK)。 用傅里叶变换红外光谱(FTIR)、核磁共振氢谱(¹H NMR)、热重分析(TG)、原子力显微镜(AFM)和扫描电子显微镜(SEM)等方法对聚醚醚酮质子交换膜的结构进行表征。 结果表明,磺酸基团被成功地在聚醚醚酮侧基上,SF-PEEK膜具有明显的亲水疏水微相分离形貌,磺酸基团相互聚集成形成离子通道。 SF-PEEK膜离子交换容量(IEC)达到1.97 mmol/g时,其电导率达到4.15×10^-2 S/cm,略低于Nafion117膜的5.67×10^-2 S/cm,但其钒离子渗透率仅为Nafion117膜的20.1%,表现出极好的离子选择性。 在钒流电池测试中,SF-PEEK膜在不同电流密度下库伦效率均高于Nafion117膜,其中IEC为1.97 mmol/g的SF80-PEEK608(80为SF的物质的量分数,608为60 ℃反应8 h)库伦效率在电流密度为40 mA/cm²时达到最大值80.9%,高于Nafion117膜的78.8%。 在自放电测试中,以SF80-PEEK608膜组装的电池的自放电时间为90 h,高于Nafion117膜的57 h。

Poly(ether ether ketone) Proton Exchange Membrane Containing Bisphenol Fluorene Unit for Vanadium Redox Flow Battery Application

Poly(ether ether ketone) (PEEK) containing methyl groups was synthesized by the aromatic nucleophilic polycondensation reaction of bisphenol fluorene unit, 4,4′-(Hexafluoroisopropylidene)diphenol, and 4,4′-difluoro-benzophenone. Poly(ether ether ketone) proton exchange membranes were post-sulfonated using concentrated sulfuric acid to give highly proton conductive sulfonic fluorenyl groups (SF-PEEK). The structure and morphology of SF-PEEK membranes were characterized by Fourier transform infrared spectroscopy (FTIR), hydrogen nuclear magnetic resonance spectroscopy (¹H NMR), thermal gravimetric analyzer (TGA), atomic force microscope (AFM) and scanning electron microscopy (SEM). The SF-PEEK membranes have strong hydrophilic/hydrophobic phase separation. The conductivity of the SF80-PFEK608 membrane (IEC=1.97 mmol/g) is 4.15×10^-2 S/cm which is lower than that of Nafion membrane (5.67×10^-2 S/cm). SF-PEEK membranes show much lower vanadium ions permeability (3.15×10^-7~1.48×10^-6 cm²/min) than that of Nafion 117 membrane (7.04×10^-6 cm²/min). As a result, the self-discharge duration of the vanadium redox flow battery (VRFB) cell with SF80-PEEK608 membrane (90 h) is longer than that of VRFB cell with Nafion 117 membrane (57 h). Furthermore, the VRFB cell with SF80-PEEK608 (IEC=1.97 mmol/g) membrane exhibits higher coulombic efficiency of 80.9% compare with that of VRFB cell with Nafion 117 membrane (coulombic efficiency of 78.8%) at current density of 40 mA/cm². The results indicate that SF-PEEK membrane is high-performance and low-cost alternative membrane for VRFB application.