Structure and Transport Properties of Ionomer Thin Films in Membrane-Electrode Assemblies
In this presentation, I will present results from density functional theory (DFT) and dissipative particle dynamics (DPD) simulations of model MEA systems in which the distribution of water and ionic groups at the interface in nanoscopic channels are compared with those in bulk membrane . The results show that the structure of thin (5-10 nm) layers of PFSA membranes is quite different to that in bulk, and may play a key role in controlling performance of MEAs. In particular, the surface coverage of sulfonic acid groups is examined as a function of substrate hydrophilicity, hydration level and equivalent weight of ionomer. The results demonstrate that the anomalously voltage losses that occur at low catalyst loadings may be due in part to reduced effectiveness of proton transport in the ionomer films.
 J.A. Elliott, D. Wu, S.J. Paddison and R.B. Moore, Soft Matter, 7, 6820-6827 (2011).