Synthesis And Performance Of Quaternary Ammonium Alkali Anion Exchange Membrane

Direct methanol fuel cells (DMFC) have attracted considerable attention as an alternative to the present power sources, since they offer numerous benefits, including high efficiency, high power density, low or zero emissions and easy fuel carriage. DMFC are expected to find wide application as a portable or mobile power, exemplified by battery for cellular phones or engine for electric vehicles. However, at present, two major technology problems in DMFC still restrict their performances and applications. One problem is the crossover of methanol through the electrolyte membrane. The other is slow methanol oxidation kinetics on the anode catalyst.It is well known that the reaction kinetics and catalytic activities of the anodic oxidation of fuel and the cathodic reduction of oxygen in alkaline media are significantly higher than those in acidic media, and less structure sensitive;and the active ion, OH", transport from cathode to anode in operation of alkaline fuel cells, which could hold back fuel crossover and convenient water management. So methanol fuel cell with alkaline electrolyte (ADMFC) might be attractive to overcome the problems of DMFC.The anion exchange membrane, a key component of alkaline direct methanol fuel cell, has dual functions of anion conduction and separation of the anode from the cathode. So we had a preliminary study on anion conducting membrane for alkaline direct methanol fuel cell applications. The results obtained are mainly as follows:1 .A route to synthesize perfluorinated anion-exchange membranes by chemical transformation is described. Starting from perfluoro sulfonic type mebrane, the functional gruop was converted succcsivcly to sulfonyl chloride, carboxylatio- n,which synthesized the middle production carboxylic acid membrane, deoxidize, chloridize and finally to quaternary ammonium alkali. quaternary monium salt. The chemical structure of membrane in each step was determined by IR spectra.2. The hydroiodic acid was first used in synthesizing the carboxylic acid membrane. It is very simpleness and easy to control. Both the surface and section of the carboxylic acid membrane are very tightness and smooth without finestras. The water content is about 14.25%(70℃), Conductivity of the membrane is about 2.31S·m^-1,the largest mechanical property is 18.70MPa(content water),ion exchange capablity is1.45×10^-3mol·g^-1.The propenties of the carboxylic acid membrane are well.3. Both the surface and section of the production quaternary ammonium alkali anion exchange membrane are very tightness and smooth without finestras. The water content rate is about 7.6%(50℃), Conductivity of the membrane is about 0.39S·m^-1,ion exchange capablity is1.2238×10^-3mol·g^-1.the open voltage of the fuel cell is 0.5 V. It is feasible that the membrane can used in ADMFC.