Preparation And Research Of LTA Zeolite/sulfonated Poly Ether Ether Ketone Composite Proton Exchange Membranes

Due to plentiful raw materials, environmentally friendly and high efficiency, the direct methanol fuel cell becomes one of the most promising fuel cells. However, its development is faced with two major technical problems: First, the widely used perfluorinated sulfonic acid proton exchange membrane is very expensive and methanol permeability coefficient is large; Second, anode catalyst used precious metals platinum is not only expensive, but the catalytic activity for methanol in the reaction is low. Therefore, it is an imperative and important research to develop low-cost and high-performance PEM used in DMFC. This thesis is based on the actual conditions and makes efforts in this direction.Judging from recent studies, polyether ether ketone is expected to become an ideal substitute of perfluorinated sulfonic acid proton exchange membrane because of its excellent performance and low price. PEEK is a poly aryl ether ketone polymers and the SPEEK is not only has a high proton conductivity, but also good mechanical strength and thermal stability. Therefore, it can be used to prepare PEM used in DMFC. In this process, high conductivity requires SPEEK has a high sulfonation degree, however, the higher the sulfonation degree, the lower dimensional stability of the film. To resolve this conflict, SPEEK is needed to modify and direct doping is a common method. In this paper, inorganic- organic direct doping is used.The main work of this article can be divided into three parts: prepared LTA zeolite used as doping by hydrothermal synthesis method. In this process, by varying the concentration, reaction temperature and reaction time, the zeolite with different particle sizes can be obtained; sulfonate polyether ether ketone to get sulfonated polyether ether ketone--SPEEK, and dope the LTA zeolite got in first part in SPEEK membrane solution to make the composite PEM; detect various properties of membranes, such as water uptake, methanol uptake, ionic exchange capacity, methanol permeability, the proton conductivity the and so on.The main results are summarized as follow: preparation of LTA zeolites with different grain sizes(500 ~ 700 nm, 200 ~ 300 nm and ~ 90nm), and it is very uniform; preparation of composite proton exchange membrane with the mass percentage of LTA zeolite being 2.5%, 5%, 7.5% and 10%, and test variety performances of composite membrane. Studies have shown that: hydrogen bonding is generated among the inorganic dopants and sulfonated polyether ether ketone, thus the swelling of composite membrane will be effectively suppressed, so the composite membrane has good dimensional stability.Methanol permeability coefficient reduced significantly, and the minimum is down to 1.90′10-7 cm2S-1 which was much less than Nafion115. Meanwhile, Proton conductivity has been improved greatly, and the maximum reach 138.7 m S·cm-1, which was larger than Nafion115. And the maximum value of the selectivity was up to 71.13′104 S·s·cm-3.