Research On Key Materials And Membrane Electrode Assembly Of Energy Transfer Devices

The direct methanol fuel cell is considered as the most promising candidates for portable electrical applications due to the high power density simiplicity as the fast recharging. However, the commericial application of DMFC is hindered by the high cost and low performance. As the core component of DMFC,Proton conductive membrane is of great charge on the high cost and low performance. The methanol permeation of proton conductive membrane leads to heavy problem on the output power. Therefore, the study is focus on decreasing the methanol permeation of proton conductive membrane by adjusting the microphase structure, surface modification. In order to make progress on the application of new proton conductive membrane, the impregnant-reduction method of fabrication MEA is also discussed. The details were listed as following:1.A series of proton exchange membranes based on sulfonated poly(arylene ether ketone)(SPAEKS) was used to study the effect of sulfonated degree and methanol permeation on performance of direct methanol fuel cells. Dependences of physical characteristics of the membranes, i. e. proton conductivity, water uptake,swelling ratio, methanol permeability and ion exchange capacity(IEC) are systematically studied. Both methanol permeability and proton conductivity of the SPAEKS membrane grow rapidly as the increase in sulfonation degree since methanol molecules and protons share the same transfer channel. However, the methanol permeability plays more important role comparing to proton conductivity.As a result, the SPEEK membrane with a medium sulfonation degree(60%) is found to yield the best performance in a DMFC due to the acquirement of balanced conductivity and methanol permeability.2.A novel solvent induced fabrication technique is developed for the preparation of the sulfonated poly(ether ether ketone)(SPEEK) based water electrolysis membrane electrode assembly(MEA). The solvent, dimethyl formamide(DMF), instead of the high pressure and temperature, is used to induce the softening of the membrane and better integration of the MEA with excellent interface compatibility. The influence of hot pressing period, the amount of polymer used in the electrode, and the temperature are investigated to optimize the performance of the MEA. The single cell performance for the water electrolysis is evaluated to optimize the fabrication parameters. It is found out that all three factors have great influences on the final cell performance and the tradeoff effects are observed due to the various states of the catalyst efficiency, triple phase boundary,the conductivity, and cell resistance. As a result, the cell performance is optimized with the MEA fabricated at 120 o C, using the catalysts to polymer weight ratio of 5:1and a 60 s hot pressing period.3.A very simple, economical impregnant-reduction method for fabrication membrane electrode assembly was reported. MEA, which was loaded with 0.1mg Pt/cm2, was fabricated by the I-R method successfully. It was shown that the prepared MEA shows 0.83 V OCV when it was assembled in hydrogen oxygen fuel cells. The TEM photography proved that the catalyst in the MEA show dimensional uniformly and was well dispersed. The Pt particle average diameter is about 2.57 nm, which is very suitable for using in the fuel cells. The MEA based on anion exchange membrane was also fabricated by impregnant-reduction method. The Pt particle average diameter is about 1.0nm, which is much smaller than the Pt nanoparticles in MEA fabricated with Nafion.