Inorganic/organic Hybrid Proton Exchange Membranes Prepared By Sol-gel Process

Proton exchange membrane fuel cells (PEMFC) are well suited for a variety of applications by their efficiency, high power densities and environment friendly nature. In PEMFC, proton exchange membrane (PEM) is one of the core components, which is the proton channel. In recent years, attention has been focused on the research of organic/inorganic hybrid PEMs. The inorganic backbone of the hybrid increases the thermal stability of the hybrid PEM, and the organic chains provide the required specific properties such as flexibility, process ability, proton conductivity, and so on.The objective of hybrid PEMs are to explore new non-fluoride PEMs, simplify process, reduce cost and increase conductivity at mediate temperature. Considering structure and property of organic/inorganic hybrid materials, hybrid PEMs based on inorganic backbone have been prepared.TEOS, PEG and PWA as precursors, SiO₂/PEG/PWA inorganic/organic hybrid PEMs have been prepared through sol-gel process. The component and structure of the hybrid membrane has been confirmed by FTIR, TGA, XRD and SEM. A "solid-liquid" model was proved, that is, PEG and PWA were filled in the micro pores in the SiO₂ backbone.The proton conductivity was investigated by ac-impedance spectroscopy. The conductivity increased with increasing PEG and PWA content, but too much of them would weaken the processing ability. PEG30PWA30 was found high to 7.682× 10^-5S . cm^-1 at room temperature but its processing ability was not good enough. Considering the processing ability and proton conductivity, PEG30PWA20 with conductivity 6.125×10^-5S . cm^-1 was the best choice.The proton conductivity increased with increasing temperature but the increasing rate didn't match Arrhenius Formula. The reasons have been analyzed.Finally, the Vehicle mechanism and Grotthuss mechanism have been employed to explain the proton conduction, and the former was the key mechanism for the hybrid PEM.