Journal of Power Sources, Vol.227, 291-299, 2013
High durable poly(vinyl alcohol)/Quaterized hydroxyethylcellulose ethoxylate anion exchange membranes for direct methanol alkaline fuel cells
Novel alkaline anion-exchange membranes composed of chemically cross-linked poly(vinyl alcohol) modified quaternized hydroxyethylcellulose ethoxylate (PVA/QHECE) are prepared. The hydroxide conductivity (sigma(-)(OH)), water and methanol uptakes, ion exchange capacity (IEC), mechanical property, dimensional and alkaline stabilities of PVA/QHECE membranes are measured to evaluate their applicability in direct methanol alkaline fuel cells (DMAFC). The effects of cross-linking time, membrane composition and catalyst dosage (H+) on membrane OH- conductivity are studied using AC impedance technique. FTIR, SEM and TG analysis are used for structural characterization of these membranes. It is found that the OH- conductivity of the membranes increases with temperature and reaches up to 7.5 x 10(-3) S cm(-1) at 90 degrees C but no apparent changes on both water uptake and methanol uptake with temperature. The methanol permeability coefficients of the membranes are in the range of 1.26 -1.72 x 10(-7) cm(2) s(-1) at 25 degrees C. In addition, the PVA/QHECE membranes show the high alkaline stability in hot 6.0 M KOH at 80 degrees C without losing their integrity and OH- conductivity during a week of evaluation. The membrane electrode assembly (MEA) fabricated with PVA/QHECE (= 1:0.25 by mass) gives an initial power density of 4.6 mW cm(-2) using 2.0 M methanol and 2.0 M KOH as the fuel and O-2 as oxidant at room temperature. (C) 2012 Elsevier B.V. All rights reserved.
Keywords:Alkaline anion exchange membrane;Chemical cross-linking;Hydroxide conductivity;Stability;Direct methanol alkaline fuel cell