A Study On Alkaline Membrane For Direct Methanol Fuel Cell

Alkaline membrane direct methanol fuel cells(AMDMFC) have attracted considerable attention,since they can atteletate methanol oxidation rate,depress the methanol crossover by the opposite direct of electro-osmosis,wide selection of catalysts and fuel cell's materials ,simplify water management. The alkaline membrane is one of the key materials, which performance could affect directly AMDMFC performance. So, the preparation of alkaline membrane has become hot in research and development.In this work, Alkaline membrane with high conductivity and thermal stability was prepared and studied.Poly(phthalazinone ether sulfone)(PPES) and Poly(phthalazinone ether sulfone ketone)(PPESK) are polymers with high thermal stability and excellent solubilities.It is not reported that PPES and PPESK were modified to prepare anion exchange membrane for direct methanol fuel cells(DMFC).Chloromethyiated poly(phthalazinon ether sulfone)(CMPPES) and Chloromethyiated poly(phthalazinon ether sulfone ketone)(CMPPESK) were prepared. It was investigated the effects of solvent,reaction temperature, reaction time,the volume of chloromethyl ether and catalyst on the contents of chlorine,and characterized by FT-IR,¹H-NMR.Chlorine contents of the polymer were determined with oxygen flask combustion technique. The low chlorine contents of polymers were prepared with chloroform as solvent and ZnCl₂ (or AlCl₃) as catalyst, and the high chlorine contents of polymers were prepared with oil of vitriol as solvent.The membranes were prepared with the different chlorine contents of CMPPES and CMPPESK respectively.Through quaternization and basification reaction, OH-form quaternized PPES(BQAPPES) and OH-form quaternized PPESK(BQAPPESK) were synthesized.The two kind of membranes are tolerant to solvent, high water content,low swelling degree, high thermal stability and good stretch resistance.Conductivity and methanol permeability of BQAPPES and BQAPPESK were tested. Conductivity of the two membranes under are all about 10^-2 S/cm at high temperature(>60℃)and close to that of Nafion membrane.Methanol permeation coefficients of the two membranes are all below 10^-7cm²/s and better than that of Nafion membrane.