Synthesis, Characterization and Performance Evaluation of Hybrid Multiblock Copolymers for Proton Exchange Membrane Fuel Cells

Abstract

Present research has been conducted for a new series of multiblock copolymers based on hydrophobic oligomer poly (arylene ether sulfone) containing 6F-bisphenol A and hydrophilic oligomer sulfonated poly (arylene ether ketone) containing pendant carboxylic acid group with varying hydrophobic block length. The ionic liquid is embedded into the synthesized multiblock copolymers to fabricate the hybrid multiblock membranes via solution casting method. The copolymers are characterized by 1H NMR, FT-IR and gel permeation chromatography (GPC) techniques. The thermal stability of the membranes has been investigated through thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) thermograms. The ionic synergism between the I.L and the acidic groups present in the multiblock copolymer provides a free pathway for the protons to travel and the resulting hybrid membranes exhibit proton conductivity in the range of (0.03 - 0.16) S/cm at 80 °C. Compared with pristine membranes, the hybrid membranes exhibit improved oxidative and mechanical stability. Moreover, the scanning electron microscopy (SEM) investigation depicts better phase separation in hybrid membranes than pristine membranes by forming ionic clusters. The membranes have been tested in H2/O2 fuel cell and their performance is compared with the state-of-art Nafion 117 membrane. For hybrid membranes, with the addition of I.L, the voltage and power densities values increased up to 0.59 V and 0.23 Wcm-2, respectively. These investigations suggest that the synthesized multiblock membranes are promising candidate for proton exchange membrane fuel cells.