Preparation And Electrochemical Properties Of The Composite Film Of Nafion-inorganic Oxides

The typical proton exchange membrane for PEMFC and DMFC is DuPont Nafion^? perfluorinated sulfonic acid polymer. The character of Nafion^? has significant influence on the performance, energy efficiency and life of the cell. So it is important to study in detail the electrochemical properties of Nafion^? and Nafion^? composite membranes.In this thesis, Nafion^?-TiO₂, Nafion^?-SiO₂ and Nafion^?-ZrO₂ composite membranes were prepared by in-situ chemical reaction method. UV-Vis, TG-DTA, XRD and IR methods were employed to characterize the structural change of the membranes. The influences of hydrothermal treatment on the structure and electrochemical properties of the membranes were studied for the first time. The results show that the water uptake of the composite membranes was larger than that of the pure Nafion membrane when the TiO₂ loading amount was within 14wt%. The methanol permeability of the membrane decreased as the TiO₂ loading amount increased. The adding of inorganic oxide particles, such as TiO₂, SiO₂ and ZrO₂, increased the ratio of amorphous phase of Nafion^? in the membranes. Hydrothermal treatment resulted in the crystal transition of TiO₂, ZrO₂ in the composite membranes. Thermal stability, acidic stability and the integrated index (σ/P) of the composite membranes improved after hydrothermal treatment. As the temperature elevating and the time increasing during hydrothermal treatment, Nafion^?-SiO₂ composite membrane contained much water, leading to the increase of methanol permeability, proton conductivity and the integrated index.