Preparation And Modification Of Proton Exchange Membranes Based On Sulfonated Poly (Aryl Ether Sulfone) For Fuel Cells

Proton exchange membrane is the key component of polymer electrolyte membrane fuel cell.In this dissertation,sulfonated poly（aryl ether sulfone）（SPAES）was used as the research object,The membranes were prepared by solution casting,cross-linked,comb-shaped and blending-crosslinking PEMs were prepared by controlling the casting conditions.The influence of these modification methods on the performance of the developed SPAES proton exchange membranes were discussed.Fluorinated poly（aryl ether）（PFAE）and phenol potassium-terminated sulfonated oligomer（SPAES-Oligomer）were synthesized by nucleophilic substitution reaction.A series of cross-linked proton exchange membranes with an ion exchange capacity（IEC）of 1.50 mmol/g were successfully prepared by dissolving a proper amount of PFAE and SPAES-Oligomer in N,N-dimethylacetamide（DMAc）and controlling the solid-liquid ratio of the casting solution and the heating program.The results showed that the comprehensive properties of the C-SPFAES-D membrane were the best,and the preparation method was:the solid-liquid ratio was 7.5%,and the heating program was 80℃for 2 h,100℃for 2 h,140℃for 6 h,160℃for 2 h.The C-SPFAES-D membrane exhibited water uptake of 23.4%,swelling ratio in the membrane in-plane direction of 5.4%,and proton conductivity of 142.9 mS/cm at 80 ^oC.A series of fluorinated sulfonated poly（aryl ether sulfone）s（PFAES）were synthesized by nucleophilic substitution reaction.After dissolving the obtained PFAES and SPAES-Oligomer in DMAc together,a series of comb-shaped proton exchange membranes（SPFAES,1.62～1.85mmol/g）were prepared by solution casting.The results showed that the formation of cross-linking structure can be avoided by controlling the casting temperature.The SPFAES had comb-shaped structure.The SPFAES-1.77 membrane showed the best comprehensive performance.Its proton conductivity reached 180.8 mS/cm at 80℃,and the maximum power density reached699.2 and 585.9 mW/cm² at 100%and 80%relative humidity（RH）,respectively,in a single H₂/O₂ fuel cell,which were higher than the maximum power density of Nafion 112 at the same conditions（618.03 and 556.9 mW/cm²,respectively）.Sulfonated poly（ether ether ketone）（SPEEK）was prepared by post sulfonation in concentrated sulfuric acid,and subsequently dissolved in dimethyl sulfoxide（DMSO）together with PFAES with various ratios.After the adding of appropriate amount of phosphorus pentoxide,a series of blending-crosslinking proton exchange membranes（CMB,1.21～1.51mmol/g）were successfully prepared by solution casting.The cross-linked membranes all were dense,and showed excellent mechanical toughness and dimensional stability,high proton conductivity and fuel cell performances.The membrane of CMB-4 with the SPEEK/PFAES mass ratio of 4:1 exhibited swelling ratio in the membrane in-plane direction less than 22%,proton conductivity as high as 219.4 mS/cm,and maximum power density of 530.5 mW/cm²at 100%RH in a single H₂/O₂ fuel cell,at 80 ^oC.