Dissipative Particle Dynamics Modeling of Polyelectrolyte Membrane–Water Interfaces

Abstract

Previous experiments of water vapor penetration into polyelectrolyte membrane (PEM) thin films have indicated the influence of the water concentration gradient and polymer chemistry on the interface evolution, which will eventually affect the efficiency of the fuel cell operation. Moreover, PEMs of different side chains have shown differences in water cluster structure and diffusion. The evolution of the interface between water and polyelectrolyte membranes (PEMs), which are used in fuel cells and flow batteries, of three different side-chain lengths has been studied using dissipative particle dynamics (DPD) simulations. Higher and faster water uptake is usually beneficial in the operation of fuel cells and flow batteries. The simulated water uptake increased with the increasing side chain length. In addition, the water uptake was rapid initially and slowed down afterwards, which is in agreement with the experimental observations. The water cluster formation rate was also found to increase with the increasing side-chain length, whereas the water cluster shapes were unaffected. Water diffusion in the membranes, which affects proton mobility in the PEMs, increased with the side-chain length at all distances from the interface. In conclusion, side-chain length was found to have a strong influence on the interface water structure and water penetration rates, which can be harnessed for the better design of PEMs. Since the PEM can undergo cycles of dehydration and rehydration, faster water uptake increases the efficiency of these devices. We show that the longer side chains with backbone structure similar to Nafion should be more suitable for fuel cell/flow battery usage.

Controlled Water Uptake in Fuel Cell Membranes with Dual Chemistry Confinement

“…The water molecules and the sulfonate groups aggregate to form the interconnected water channels, surrounded by hydrophobic backbones. The observation of the phase behavior of the Nafion membrane at different activities in our model is consistent with the previous experimental and simulation results. , …”

“…The observation of the phase behavior of the Nafion membrane at different activities in our model is consistent with the previous experimental and simulation results. 34,43 The relationship between the membrane thickness and the water content is plotted as shown in Figure S1. The thickness of the Nafion membrane increases linearly with the water content.…”

DPD Modelling of the Self- and Co-Assembly of Polymers and Polyelectrolytes in Aqueous Media: Impact on Polymer Science

“…Other types of important polymeric materials are the hydrated selectively permeable membranes (particularly the Nafion membranes), which play a crucial role in fuel cells. Their study has represented a hot topic for experimentalists [266,267], theoreticians and computer scientists for several decades, and it is not surprising that several recent DPD studies have addressed the fuel cell membranes [124,253,[268][269][270][271][272][273]; the last two papers unfortunately study the electrically charged system without explicit electrostatics, which restricts their impact. On the other hand, the papers on hydrated membranes published by the Neimark group [124,271,273] are of special interest because they also contribute significantly to the methodological progress in DPD modelling.…”

Coarse-Grained Modeling of Ion-Containing Polymers

“…Recently, Sengupta and Lyulin found that Aciplex, which has longer side chains than Nafion, exhibits faster water uptake and a higher rate of water cluster formation preserving the shape of the clusters. The results suggest that the longer side chain Aciplex may be promising for use in fuel cells and flow batteries …”