Dissipative particle dynamics approach for nano-scale membrane structure reconstruction and water diffusion coefficient estimation

The membrane is often considered as the heart of the proton exchange membrane fuel cell (PEMFC), and it is of pivotal importance for the involved transport phenomena and performance of the entire PEMFC. The Nafion® membrane is the most commonly used type of membrane in PEMFCs. In this paper, the nano-scale structure of the Nafion® membrane is reconstructed using dissipative particle dynamics. The average water pore sizes of the equilibrated membranes are estimated by employing the radial distribution function, and the reconstructed nano-scale membranes are then used to evaluate water diffusion within the membrane by calculating the mean square displacement. The tortuosity of the membrane is evaluated by comparing the diffusivity of the membrane to that of a limiting case of cylindrical channels. Important findings from this study are presented by the membrane structures, water diffusivity at different water saturations, and calculations of the tortuosity within the membrane.