Studies On Structure And Performance Of Proton Exchange Membranes For PEMFCs

Proton exchange membrane (PEM) is one key component of fuel cells, which has double functions of conducting protons, separating fuels and oxidant. At present the performance and price of sulfonic acid PEMs used in PEMFC are deeply concerned. The work in this thesis focuses on the two aspects mentioned above.Firstly, proton conducting and micro structure of perfluorinated and partially fluorinated PEMs were investigated, micro ionic-cluster structure of fluorinated PEMs were confirmed, influence of EW on ionic-cluster spacing was validated. Proton conducting capacity is dominated by proton conductivity and equivalent conductivity not by proton volume concentration, micro structure was visibly characterized by TEM.The SPTFS/PTFE composite membranes were synthesized by dissolving SPTFS polymer and impregnating the obtained SPTFS solution into the pores of porous PTFE films. In the process, the gravity dragged SPTFS solution into the pores of the PTFE films. The price of SPTFS/PTFE composite membranes was greatly reduced by using cheap partially fluorinated polymer instead of expensive perfuorinated resin. Due to the enforcement of PTFE films, in wet condition, the mechanical strength and dimensional change of the composite membrane are better than that of homogeneous membranes and close to that of Nafion? Therefore very thin membrane can be obtained. The fuel cell performances of the composite membrane are equal or superior to those of commercialized Nafion?membranes.Some primary study on synthesis and performance of non-fluorinated SPEEK PEM and SPEEK self-humidifying membrane was carried out.