Preparation and characterization of proton exchange membrane based on SPSEBS/PSU blends for fuel cell applications

Proton-conducting polymer membranes are used as an electrolyte in the so-called proton exchange membrane fuel cells. Commercially available membranes are perfluosulfonic acid polymers, a class of high-cost ionomers. This paper examines the potential of polymer blends, namely those of sulfonated polystyrene ethylene butylene polystyrene (SPSEBS) and polysulfone (PSU), in the proton exchange membrane application. SPSEBS/PSU blends were prepared by solvent evaporation method. SPSEBS membranes exhibited good conductivity, flexibility and chemical stability while they had poor mechanical stability. In an effort to improve the mechanical properties of SPSEBS while maintaining the initial conductivity, it was incorporated with PSU. The obtained membranes were characterized in terms of conductivity, ionic exchange capacity and water uptake. Blend membranes were studied by FTIR spectroscopy and X-ray diffraction. The morphology of the membranes was studied by scanning electron microscope (SEM). Thermal stability of the membranes was studied by TGA and DSC. Mechanical strength was studied by UTM. This paper presents results of recent investigations to develop an optimized in-house membrane electrode assembly (MEA) preparation technique combining catalyst ink spraying and assembly hot pressing. Easy steps were chosen in this preparation technique in order to simplify the method, aiming at cost reduction. The influence of MEA fabrication parameters like electrode pressing or annealing on the performance of hydrogen fuel cells was studied by single cell measurements with H2/O2 operation. Carbon cloth was used as a gas diffusion layer (GDL) and the composition of electrode inks was optimized with regard to most favorable fuel cell performance. Commercial E-TEK catalyst was used on the anode and cathode with Pt loadings of 0.125 and 0.37 mg/cm2, respectively. The MEA with best performance delivered approximately 0.50 W/cm2, at room temperature. The methanol permeability and selectivity showed a strong influence on DMFC performance.