新型细菌纤维素基阻醇质子交换膜的制备及表征

Preparation and Characterization of Novel Bacterial Cellulose-Based Methanol-Resistant Proton Exchange Composite Membranes

以凝胶贴附法,在Nafion膜两侧贴附细菌纤维素(BC)膜,制备出BC/Nafion/BC夹心复合膜,以期结合Nafion膜的良好导电性和BC膜的优秀阻醇性,制备新型阻醇质子交换膜。利用扫描电镜、热重分析对其形态结构和热稳定性进行研究,并对夹心膜的尺寸稳定性、质子传导率和甲醇渗透率进行表征。结果发现,复合膜的夹心结构紧密,热稳定性良好,尺寸稳定性比市售的Nafion膜有很大改善,提高了43%。夹心膜的质子传导率随温度的升高明显上升,虽略低于Nafion膜,但是甲醇渗透率明显降低一个数量级,阻醇性能得到了很大改善。组装成电池后,单电池开路电压达到922 mV,最大发电功率密度为7.2 mW/cm2。该结果表明夹心复合膜作为新型质子交换膜应用于直接甲醇燃料电池中具有很大潜力。

In order to combine the good conductivity of Nation with the excellent methanol- blocking capability of bacterial cellulose to produce a novel methanol-resistant proton exchange membrane, BC/Nafion/BC sandwich proton exchange composite membranes were prepared through attachment of bacterial cellulose membranes on two sides of a Nation film. The molecular structure and thermal stability were studied by scanning electron microscopy and thermogravimetric analysis. Dimensional stability, proton conductivity and methanol permeability were studied for different sandwich membranes. The results showed that sandwich composite membranes had a compact structure and a good thermal stability. Compared with commercial Nation films, the dimensional stability of sandwich composite membranes had been improved by 43%. In addition, along with the increase of temperature, proton conduction rate of the sandwich membranes rose apparently, which was slightly lower than that of the commercial Nation films. However, the methanol permeability was obviously reduced from 10-6 to 10-7, which means that methanol- resistant properties have been greatly improved. Single-cell performances showed that the membrane electrode assembly fabricated with the sandwich membranes reached the open-circuit voltages of 922 mV and the initial power densities of 7.2 mW/cm^2, respectively. The results indicate that the BC/Nafion/BC sandwich composite membranes have a great potential if applied in direct methanol fuel cells as novel proton-conducting membranes.