A novel polyion complex membrane was synthesized for direct methanol fuel cell application through the blending of the natural biopolymer sodium alginate (SA) with the synthetic polymer Pebax [poly(ether-block-amide)]. The blend was covalently crosslinked with glutaraldehyde (GA) and sulfonated with sulfuric acid (H 2 SO 4 ), after which characterization by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffractometry, thermogravimetric analysis, and universal testing machine techniques was carried out. The SA-Pebax-GA-H 2 SO 4 membrane exhibited a high ion-exchange capacity of 2.1 mequiv/g, an optimum water sorption of 17.3%, and a low methanol sorption of 9.5%. A desirably low methanol permeability of 9.25 3 10 28 cm 2 /s and a high proton conductivity of 0.067 S/cm were obtained as against corresponding values of 1.82 3 10 26 cm 2 /s and 0.077 S/cm reported for a commercial Nafion 117 membrane. Moreover, a high selectivity of 6.5 3 10 5 Ss/cm 3 with a power density of 0.17 W/ cm 2 was achieved with the indigenous blend membrane at a potential of 0.34 V. Molecular dynamics simulation was performed along with the estimation of fractional free volume to explain the transport behavior of water and methanol molecules through the membrane.
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