Molecular Dynamics Simulation Studies on the Micromorphology and Proton Transport of Nafion/Ti3C2Tx Composite Membrane

The perfluorosulfonic acid (PFSA) membrane doped with two-dimensional conductive filler Ti3C2Tx is a fuel cell proton exchange membrane with high application potential. Experimental studies showed that the proton conductivity of Nafion/Ti3C2Tx composite membrane is improved significantly compared with that in pure Nafion. However, the microscopic mechanism of doping on the enhancement of membrane performance is remain unclear now. In this work, molecular dynamics simulation was used to investigate the microscopic morphology and proton transport behaviors of Nafion/Ti3C2Tx composite membrane at the molecular level. The results shown that there were significant differences about the diffusion kinetics of water molecules and hydroxium ions in Nafion/Ti3C2Tx at low and high hydration levels in the nanoscale region. With the increase of water content, Ti3C2Tx in membrane was gradually surrounded by ambient water molecules to form a hydration layer, and forming a relatively continuous proton transport channel between Nafion polymer and Ti3C2Tx monomer. The continuous proton transport channel could increase the number of binding sites of proton and thus achieving high proton conductivity and high mobility of water molecules at higher hydration level. The current work can provide a theoretical guidance for designing new type of Nafion composite membranes.