Controlled sulfonation of poly(ether sulfone) using phthalic anhydride as catalyst and its membrane performance for fuel cell application

Abstract

Proton exchange membrane (PEM) fuel cells are one of the most emerging alternative energy technologies under development. A novel proton exchange membrane sulfonated polyethersulfone (SPES) was developed by homogeneous method using phthalic anhydride as catalyst and chlorosulfonic acid as sulfonating agent to control the sulfonation reaction. The method of sulfonation was optimized by varying the reaction time and concentration of the catalyst. The structure of the SPES was studied by 1H-Nuclear Magnetic Resonance, Fourier Transform Infra Red Spectroscopy and X-ray diffraction. The extent of sulfonation was determined by ion exchange capacity studies. The thermal and mechanical stabilities were studied using thermogravimetric analysis (TGA) and Dynamic Mechanical Analysis (DMA) respectively. DMA results show that the storage modulus increased with increase in degree of sulfonation (DS) and water uptake of SPES increased with DS. The proton conductivity of SPES (34% DS) measured by impedance spectroscopy was found to be 0.03S/cm at 80%RH and 100°C. Also, current-voltage polarization characteristics of SPES membranes offer a favourable alternative PEM due to the thermal stability and cost effective than perfluorinated ionomers.

Keywords

• PEM; Sulfonated poly (ether sulfone); Phthalic anhydride; 1H-NMR; DMA
• PEM
• Sulfonated poly (ether sulfone)
• Phthalic anhydride
• 1H-NMR
• DMA