Preparation And Performance Study Of Nanocomposite Membranes Made Of Nafion^? And Titanium Dioxide With Modification Of Surface For PEMFC Applications

Proton exchange membranes are a key component in the development of proton exchange fuel cells(PEMFCs), which are devices for directly transforming chemical energy into electrical energy without producing waste products and environmental problems. Sulfonated perfluoro-polymers like Nafion(?), although having high proton conductivity, have the disadvantage of high cost and high methanol crossover. Consequently, there is a considerable amount of research on seeking alternatives for Nafion(?). Modifications on present PEM materials aimed at property enhancements is also an effective approach to obtain suitable PEMs for PEMFC.In this thesis, nano surface engineering technology has been applied to the surface modification of TiO2 and we have prepared two kinds of modificatory nano particles. Then they were added to the Nafion(?) membrane to prepare two new composite membranes, the structure and properties of which were studied later. Specifically, the content in this thesis is listed below:1. Two kinds of modificatory nano particles have been synthetized through silane coupling agent treatment, the structure and particle size of which were characterized by FT-IR, TEM and LPSA. The right synthetic routewe was selected and confirmed by the method of monitoring reaction in a period of time.2. C2 and D1 were added to the Nafion(?) membrane to prepare composite membranes Nafion(?)/D1 membrane and Nafion(?)/C2 membrane through the method of file casting firstly. D1 and C2 are uniformly distributed in composite membranes and good compatibility with Nafion(?) without obvious phenomenon of reunion as observed by SEM photographs. The TG experiment shows that addition of D1 and C2 to the Nafion(?) have not slowed the degradation of sulfonic acid in composite membranes. Study has focused on the trend of water content with different fillers content at different temperature and change of proton conductivity in impact of water uptake. It was observed that composite membranes have good high water-uptake. Study has also focused on methanol permeability with different fillers content at different temperature, which was measured by membrane diffusion method. The results showed that compared with Nafion(?) membrane, methanol permeability of composite membranes decreased by about one order of magnitude. The presence of D1 and C2 in the compsite membranes significantly decrease the methanol permeability.