Chemically-modified Nafion®/poly(vinylidene fluoride) blend ionomers for proton exchange membrane fuel cells

Miscible Nafion®/poly(vinylidene fluoride) blend membranes are prepared and characterized PVdF = poly(vinylidene fluoride). The membranes have high miscibility above a 60 wt.% Nafion® fraction when both polymers are dissolved in a solvent mixture of N,N′-dimethylacetamide and 2-propanol. Despite the high miscibility, the extremely hydrophobic PVdF component reduces the water uptake of Nafion®/PVdF blend, and the proton conductivity is much lower than that of a Nafion® 115 membrane even with a high weight fraction of Nafion®. To improve water affinity and proton conductivity, PVdF is chemically-modified by means of a dehydrofluorination reaction and H2SO4 doping prior to solution blend. The chemically-modified Nafion®/PVdF blend membrane shows similar conductance to Nafion® 115 without any auxiliary fillers. Nafion®/PVdF blend membranes of not, vert, similar35 μm thickness are hot-pressed between catalyzed carbon paper ELAT® electrodes. A 25 cm2 single cell delivers a maximum power of about 440 mW cm−2 at 900 mA cm−2 under H2/O2, which is comparable to the performance of Nafion® 115 under the same operating conditions.