Synthesis And Modification Of Environmental-friendly Sulfonated Polysulfone Proton Exchange Membranes

Energy shortages and environmental pollution have been two global problems that restrict human society and economic development. All the world have made an agreement on energy sustainable development and changing the energy consumption structure as soon as possible. Fuel cell is an emerging green energy device. In theory, it can produce current as long as fuel and oxidant are added to it constantly. Proton exchange membrane fuel cell (PEMFC) which has many outstanding advantages, such as highly efficient energy-saving, low noise, long life, has been a world's hot spot.Proton exchange membrane (PEM), the key part of PEMFC, not only separates the fuel from oxidant to avoid direct contact, but also transfers protons from anode to cathode. The properties of PEM would considerably impact on the PEMFC performances such as energy efficiency and service life.Nafion membrane, represented as a commercial PEM, is easy to cause environmental pollution in the course of using, and abandoned Nafion membrane is difficult to deal with and has a potential hazard to the environment; Besides, Nafion membrane has several problems, such as high methanol permeability, low proton conductivity at high temperature, etc. A series of environmental-friendly SPAES and bi A-SPAES membranes with different sulfonated degree (Ds), TiO2/SPAES and TiO2/bi A-SPAES composite membranes, and PWA/bi A-SPAES composite membranes were prepared in order to make PEMFC become a green energy device, and at the same time improve the overall performance of PEM. The structures of these membranes were characterized, and the properties of them were systematically studied, hoping to look for alternative material for Nafion membrane.A series of SPAES polymers were prepared by nucleophilic substitution reaction. The results of intrinsic viscosity showed that of their high molecular weight. The chemical structure of SPAES polymer was confirmed by FT-IR and 1H NMR spectra. All the polymers could be successfully cast into tough membranes. It was found that SPAES membranes had good thermal stability and mechanical properties by detecting, and Ds of SPAES had a great impact on the performance of membranes. The proton conductivities and methanol diffusion coefficient of SPAES membranes increased with the increase of Ds. The proton conductivity of SPAES membrane with Ds0.8 at 80°C and 100°C were 0.116S/cm and 0.126S/cm, respectively, which were higher than those of Nafion 117 membrane (0.114S/cm and 0.117S/cm); What's more, the methanol diffusion coefficient of SPAES membrane with Ds0.8 was 8.4×10-7 cm2/s, which was lower than that of Nafion 117 membrane (2.1×10-6cm2/s).A series of bi A-SPAES polymers were prepared by nucleophilic substitution reaction. The results of intrinsic viscosity showed that of their high molecular weight. The chemical structure of bi A-SPAES polymer was confirmed by FT-IR and 1H NMR spectra. All the polymers could be successfully cast into tough membranes. It was displayed from detection that bi A-SPAES membranes had good thermal stability and mechanical properties, and Ds of bi A-SPAES had a great impact on the performance of membranes. The proton conductivities and methanol diffusion coefficient of bi A-SPAES membranes increased with the increase of Ds. The proton conductivity (0.10-0.15S/cm) of bi A-SPAES membrane with Ds1.2 was higher than that of Nafion 117 membrane (0.095-0.117S/cm) in all the experiments temperature conditions; and the methanol diffusion coefficient of bi A-SPAES membrane with Ds1.2 was 8.5×10-7cm2/s, which was lower than that of Nafion 117 membrane.Inorganic particles can increase sanction between water molecule and improve hydration because of their good hydrophilicity. They can ensure to keep adequate humidity in PEM at high tempereature, and therefore improve proton conductivity of the membranes at high temperature. We prepared composite PEM material with high performance by mixing inorganic particles in order to aviod the problems of low proton conductivity of the membranes with low Ds and high methanol diffusion coefficient of the membranes with high Ds, and improve the performance of PEM and exploit high-performance PEM.A series of TiO2/SPAES (Ds0.8, Ds1.0 and Ds1.2) and TiO2/bi A-SPAES (Ds0.8, Ds1.0 and Ds1.2) composite membranes with various contents of TiO2 particles were prepared through sol-gel reactions. FT-IR spectra and SEM images indicated the TiO2 particles were well dispersed within SPAES and bi A-SPAES polymer matrix. The results showed that TiO2/SPAES and TiO2/bi A-SPAES composite membranes had good thermal stability and mechanical properties by detecting, and the contents of TiO2 particles had a great impact on the performance of these composite membranes. The incorporation of TiO2 particles induced higher proton conductivity than the pure membranes and at the same time improved the property of methanol resistance. A series of PWA/bi A-SPAES (Ds0.4 and Ds0.2) composite membranes with various contents of PWA were prepared by blending method. FT-IR spectra and SEM images indicated the PWA particles were well dispersed within polymer matrix. PWA/bi A-SPAES composite membranes had good thermal stability and mechanical properties by detecting, and the contents of PWA particles had a great impact on the performance of these composite membranes. The introduction of PWA particles induced higher proton conductivity and methanol diffusion coefficient than the pure membranes, but the methanol diffusion coefficient was still much lower than that of Nafion 117 membrane.Summary, the comprehensive performance of SPAES membrane with Ds0.8 and bi A-SPAES membrane with Ds1.2 were better than others in this study. They not only improved the defect of low proton conductivity at high temperature, but also improved the defect of high methanol diffusion coefficient; The introduction of TiO2 particles improved the properties of methanol resistance and proton conductivity of SPAES and bi A-SPAES membranes with high Ds; The introduction of PWA particles improved the property of proton conductivity of bi A-SPAES membranes with low Ds. Therefore, the membranes prepared in this study were expected to be candidates for PEM of material in DMFC which make it a real green and effective energy device.