Cross-linked Sulfonated Poly (arylene ether sulfone)s Copolymer for Proton Exchange Membrane Fuel Cells

  • Shaoguang Feng, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing, 100084, China
  • Prof Yuming Shang, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing, 100084, China
  • Dr Yan Chen, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing, 100084, China
  • Prof Xiaofeng Xie, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing, 100084
  • Prof Jingming Xu, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing, 100084

    • The proton exchange membrane is one of the key components of Polymer Electrolyte Membrane Fuel Cells (PEMFCs), which serves as the barrier for fuels and the electrolyte for transporting protons from the anode to cathode.
    Sulfonated poly(arylene ether sulfone)s (SPAES) are good candidates due to their good acid and thermal oxidative stabilities, high glass transition temperatures and excellent mechanical strengths.
    These sulfonated aromatic polymer membranes require a high sulfonation level to achieve sufficient proton conductivity. Unfortunately, for linear polymers, such a high sulfonation level makes them excessively water-swollen or soluble in water. In this case, highly sulfonated polymer membranes lose their mechanical properties and become unavailable in PEMFCs applications. Cross-linking could be a simple and powerful solution to control such indispensable properties.
    Commercially available 4,4’-dichlorodiphenylsulfone (DCDPS) was successfully disulfonated with fuming sulfuric acid to yield 3,3’-disodiumsulfonyl-4,4’-dichlorodiphenylsulfone (SDCDPS). Subsequently, DCDPS and SDCDPS were systematically reacted with 4,4’-biphenol and 3,3’-diallyl-4,4’-dihydroxybiphenyl under nucleophilic step polymerization conditions to generate a series of high molecular weight copolymers(Scheme1). The resulting SPAES solution was mixed with benzoyl peroxide (BPO), which was casted onto glass substrate, and heated to 120℃ to form cross-linked membranes.
    By cross-linking methodology, the synthesized polymers could fulfill the contradiction of the high sulfonation degree and the dimensional stability. The cross-linked membrane obtained from above polymer had proton conductivity (0.11S/cm) when compared to the Nafion 117 (0.10S/cm) at 30℃ 100% humidity. Moreover, the crosslinked reaction can obviously improve the oxidative stability of the prepared membrane without the loss of proton conductivity.