Study And Preparation On Proton Exchange Membrane For Sulfonated Poly (Ether Ether Ketone) Doped By Ionic Liquids

Proton Exchange Membrane Fuel Cell (PEMFC) has wide applications in automotive industry and stationary power source for its high energy conversion efficiency and non-pollution. We can solve many problems,such as catalytic agent poisoning, simplified for the water and heat management system and the electrochemistry kinetics for fuel cell's anode and cathode by increasing PEMFCs operation temperature. However, traditional proton exchange membrane, for example Nafion membrane, has limited applications in high temperature fuel cells for its higher manufacturing cost and the strongly humidity-dependent proton conductivity as well as lower glass transition temperature. Therefore, it is critical to develop a new membrane to make fuel cell work in high temperature. In this thesis, the degree of sulfonated well-controlled for sulfonated poly (ether ether ketone) (SPEEK) and compostie membrane based on the SPEEK and ionic liquids were prepared, and we have done research through different ionic content and membrane processing; meanwhile,we aslo make preliminary analysis for the proton transport mechanism under high temperature, it comes to the following conclusions:(1) A series of controllable degree of sulfoanted SPEEK were synthesized and its show good thermal stability and excellent mechanical properties at high temperature. A different type of composite membrane based on the SPEEK and ionic liquids (ILs) were aslo prepared and we found that the composite membrane have good proton conductivity and mechanical strength when the ILs content is 60Wt%. Electrostatic fore microscopy (EFM) revealed that there are surface potentia differences on the membrane surface because of its free electricity charge which provides driving force for the proton transportation;(2) Leaching experiment results:proton conductivity dramatically drops when the ILs loses; and also significant changes occur in its microstructure. The ILs loss strongly depends on the substituent group in the imidazole ring:the longer length of N-substituted alkyl chain, the lower chance of the ILs loss. decyl (C8) group has lower ILs loss than butyl group (C4). However, for composite membrane is designed for the high temperature use. The ILs loss will not be huge as more water produced by the electrochemistry reaction, the leaching of ILs for high temperature fuel cell is still to be further investigated and proved.(3) There are two different proton transport mechanisms for SPEEK/ILs composite membrane:Grutthuss mechanism is dominated when the fuel cell operated under low temperature or in the presence of water while Vehicle mechanism is controlled at high temperature or under anhydrous condition.