Change in morphology of fuel cell membranes under shearing

Abstract

The effect of shearing on Nafion/water systems was investigated using Dissipative Particle Dynamics (DPD). This simulation approach has been shown to accurately reveal the morphology of such systems in the steady state. We first confirmed that the length of the Nafion chain, 5 and 20 DPD units, has no influence on the overall morphology for four different concentrations, 10, 20, 30, and 40%, of water. Shearing effects with 0.05 and 0.2 rates were then studied according to the Nafion chain length, 5 and 20 DPD units, and water content, 10 and 30%. It was shown that low water contents and long chain length lead to the formation of water-rich tubes, aligned with the shear direction. The formation of such channels can ultimately lead to an increase in the proton conductivity at low humidity. The size of these water tubes thus results from a combined influence of shear strain, chain relaxation time, interfacial tension and water content.