Highly stable hydroxyl anion conducting membranes poly(vinyl alcohol)/poly(acrylamide-co-diallyldimethylammonium chloride) (PVA/PAADDA) for alkaline fuel cells: Effect of cross-linking

Highly stable hydroxyl anion conducting membranes have been developed using poly(vinyl alcohol) (PVA) as matrix by incorporation of poly(acrylamide-co-diallyldimethylammonium chloride) (PAADDA) as anion charge carriers. In order to clarifying the cross-linking effect on membrane performances, two series of PVA/PAADDA membranes were prepared by direct and indirect chemical cross-linking ways, and have been characterized in detail at structural and hydroxyl ion (OH-) conducting property by FTIR spectroscopy, thermal gravity analysis (TG), scanning electron microscopy (SEM), water sorption, ion exchange capacity and alkaline resistance stability. The OH- conductivity of the membranes increased with increasing the content of PAADDA in polymer and temperature, and reached 0.74-12 mS cm(-1) with direct cross-linking way and 0.66-7.1 mS cm(-1) with indirect cross-linking way in the temperature range 30-90 degrees C. The membranes are found to have the same IEC values but the membranes with direct cross-linking way showed higher water uptake than that with indirect cross-link one. Both membranes showed the thermal stability above 200 degrees C, and can integrity in 100 degrees C hot water and methanol solution, where the swelling are better suppressed as high dense chemical cross-linkages in PVA network. Very low methanol permeability (from 1.82 x 10(-7) to 3.03 x 10(-7) cm(2) s(-1)) in 50% methanol solution was obtained at 30 degrees C. Besides, the chemical stability in 80 degrees C, 6 M hot alkali conditions and long-term stability of 350 h in 60 degrees C hot water revealed that the PVA/PAADDA membranes are promising for potential application in alkaline fuel cells. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.