Layer-by-layer self-assembly of CHI/PVS-Nafion composite membrane for reduced methanol crossover and enhanced DMFC performance

A novel CHI/PVS-Nafion composite membrane was fabricated to address the operational issue of severe methanol crossover in DMFC by layer-by-layer (LbL) self-assembly of cationic polyelectrolyte Chitosan (CHI) and anionic polyelectrolyte polyvinyl sulfuric acid (PVS) on Nafion membrane. The bilayers were successfully deposited onto Nafion membrane surface, which was confirmed by FTIR spectra, FESEM and AFM images. The thermal property and the water uptake of the LbL composite membrane were investigated. With bilayers formed onto the Nafion membrane, methanol permeability has been reduced expectedly but at an expense of proton conductivity to some extent. It was found that the concentration of polyelectrolyte solutions (used to modify the Nafion membrane) and the number of deposited bilayers are key factors affecting the proton conductivity and methanol permeability of the composite membrane. However, the characteristic factors (ratio of proton conductivity to methanol permeability) of the composite membranes were all higher than that of Nafion 117 and the single cell performance has been dramatically enhanced with the layer-by-layer self-assembled of CHI/PVS Nafion composite membrane. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.