咪唑接枝交联型磺化聚醚醚酮质子交换膜的制备及在直接甲醇燃料电池中的应用

Cross-linking of Imidazole-grafted Sulfonated Poly( ether ether ketone) as Proton Exchange Membranes for Direct Methanol Fuel Cells

通过咪唑接枝、共价交联制备出交联型咪唑改性磺化聚醚醚酮(SPEEK)质子交换膜.通过接枝咪唑可以大幅提高质子电导率,25℃下电导率可达0.14 S/cm,高于Nafion膜(0.086 S/cm),并随着交联度的增加,质子电导率逐渐降低,但交联膜的致密网络结构使得甲醇渗透明显降低,当交联度为20%时膜的电导率和甲醇选择性分别高达0.105 S/cm和4.57×10~5S·s/cm^3,实现了质子电导和甲醇阻隔的均衡.通过共价交联,膜的氧化稳定性和尺寸稳定性大幅提升.采用交联度为20%的改性SPEEK膜,被动式直接甲醇燃料电池(DMFC)在25℃下的最大输出功率密度达29.7 mW/cm^2,可与商业化Nafion 115膜相媲美,展现出良好的应用前景.

Sulfonated poly(ether ether ketone)(SPEEK)membrane is considered as a promising candidate to replace the Nafion membrane for the direct methanol fuel cell(DMFC)due to its high proton conductivity and excellent methanol resistance.However,the SPEEK always suffers the poor chemical stability.Herein,a novel imidazole functionalized cross-linked SPEEK membrane was synthesized via covalently cross-linked method.The results show that the modified SPEEK membrane exhibits greatly enhanced proton conductivity(0.14 S/cm at 25℃)in comparison with the Nafion 115 membrane(0.086 S/cm)by introducing the imidazole groups.Increasing the cross-linking degree of the membranes leads to a decrease in proton conductivity and a great reduction in methanol permeability due to the more compact network structure.When the cross-linking degree reaches 20%,the proton conductivity and methanol selectivity are 0.105 S/cm and 4.57×10 5 S·s/cm 3,respectively,demonstrating a good balance between proton conductor and methanol separator.Importantly,the oxidative and dimensional stabilities of cross-linked SPEEK membrane are significantly improved.A passive DMFC incorporated with the optimized Im-C-SPEEK-20 membrane delivers a peak power density of 29.7 mW/cm 2 at room temperature,close to that with Nafion 115(31.8 mW/cm 2),suggesting a promising application potential in DMFCs.