4-Methylbenzenesulfonic Acid as an Alternative Proton Conducting Functional Group for Elevated Temperature Polymer Electrolyte Membranes Fuel Cell

Abstract

Polysulfones carrying (4-Methylbenzenesulfonic Acid) side chains were prepared and investigated for use as proton-conducting fuel-cell membranes.The resulting ionomers were cast into membranes and properties such as mechanical and thermal stability, ion-exchange capacity, proton conductivity and water sorption were evaluated. Sulfonations of membrane were achieved by varying the degree of sulfonation (DS) in reaction time.The presence of sulfonic group after sulfonation process in the modified polymers was characterized by nuclear magnetic resonance (NMR), elementary analysis and infrared spectroscopy (FT-IR). Fourier Transform Infared (FTIR) were used to verify and it was clearly confirmed the presence of SO₃ stretching bond at frequency 1030 cm^-1 Thermo gravimetric analysis (TGA) show that these membranes are thermally stable up to 390°C  in dry air, which implying that they have a good potential to be used as the membranes for high-temperature PEM fuel cells. Under anhydrous situation, ionic conductivity of the membrane reach the highest point value of 5.02×10^-4 at 150 °C associated with the activation energy of (22.04 kJ mol^-1) for proton transport. Scanning electron microscopy was used to examine the surface morphology of the formed membrane. Characterizations of different degree of sufonated membranes were conducted through elemental analysistal, Fourier Transform Infared (FTIR) and swelling test.

Keywords: fuel cell, polymer electrolyte membrane, Polysulfone (PSF), 4-Methylbenzenesulfonic Acid (MBSA), benzyl chloride.