Atomistic analysis of hydration and thermal effects on proton dynamics in the Nafion membrane

An investigation of the proton dynamics inside a Nafion membrane has been carried out by molecular dynamics simulations. The atomistic analysis was performed at four different hydration levels (4.21, 8.61, 12.65, and 21.60 wt %) and three operation temperatures (333, 343, and 353 K). The simulation results show a distinct ionic segregation toward the hydrophobic (near fluorocarbon) and hydrophilic (close to the sulfonated acid groups) regions inside the membrane. The number of water clusters at high hydration levels increases significantly compared to the lower cases. A higher temperature tends to magnify the size of the hydrophilic phase; both increase the proton diffusivity. Apart from the effect analysis, this paper also explains the nanoscopic mechanism of the proton transport and further relates it to the molecular structure of the electrolyte membrane. (c) 2008 The Electrochemical Society.