Characteristics and direct methanol fuel cell performance of polymer electrolyte membranes prepared from poly(vinyl alcohol-b-styrene sulfonic acid)

Block type polymer electrolyte membranes (PEMs) were prepared by casting an aqueous solution of a block copolymer, poly(vinyl alcohol-b-styrene sulfonic acid) (PVA-b-PSSA), and by cross-linking the PVA chains with glutaraldehyde (GA) solution at various GA concentrations to investigate the effect of the cross-linking conditions on the properties of the block-type PEMs. The proton conductivity and the permeability of methanol through the block-type PEMs decreased with increasing GA concentration. The permeability coefficient through the block-type PEM prepared under the conditions of cGA = 0.05% is about 6 times lower than that through Nafion115® under the same measurement conditions. A test cell for a direct methanol fuel cell constructed using the block-type PEMs delivered 32.4 mW cm−2 of Pmax at 116 mA cm−2 of load current density at 1 M methanol solution, which is almost the same value obtained with Nafion115®. However, at high methanol concentrations (>9 M), the Pmax of the block-type PEM was 17.8 mW cm−2, and was 86% higher than that of Nafion®115.