Fundamental insights into structure-performance relationship for proton conductivity enhancement through polymer electrolyte membrane in Proton Exchange Membrane Fuel Cell

Abstract

The efficiency of a polymer electrolyte membrane fuel cell (PEMFC) is limited by the proton conductivity of polymer electrolyte membrane (PEM). Local structural variation with hydrophobic-hydrophilic zone segregation in PEM affects proton conductivity profoundly. There is a lack of elemental theoretical model to predict proton transport in novel PEMs with a wide range of compositions and structures. In this work, the first-principle based meso-scale modelling has been attempted to address localised structural variations. The membrane is divided into repetitive lattice of uniform structure. The segregated domains follow periodic or random arrangements. The applicable governing equations are solved numerically under appropriate boundary conditions. The system parameters are recognized and their effects are thoroughly investigated. For the futuristic PEMs, the effect of variation in zone arrangement, its size and its gradual change was investigated. The model was validated with reported data of Nafion membranes with successful prediction of conductivity at different operating temperature and humidity. A phase-space plot was generated for use as a straight-forward tool for prediction of proton conductivity at different operating environment for varying segregation level. The developed model can enlighten the transport mechanism through any existing and futuristic PEMs, scale-up and design them according to the application requirement.