Water behavior at PEMFC triple phase boundary: Exploring ionomer and catalytic layer effects via molecular dynamic simulations and NMR experiments

Abstract

Polymer electrolyte membrane fuel cells (PEMFCs) offer a clean and efficient energy generation technology. However, optimizing their performance in terms of water transport through the electrolyte membrane remains a challenge. In this study, we employ molecular dynamics simulation and nuclear magnetic resonance (NMR) experiments to investigate the influence of carbon materials and membrane thickness on water diffusion within the triple phase boundary of a PEMFC. Our theoretical investigation highlights the significant impact of Nafion content on water morphology within the system. The structural analysis reveals the intricate interplay between material properties and water behavior in confined environments. The formation of water channels facilitated by the ionomer enhances water mobility, while excessive ionomer content leads to reduced diffusion coefficients. Experimental measurements using NMR diffusion validate the correlation between our simulation results and real-world observations. Furthermore, our Molecular Dynamic (MD) and NMR studies identify the optimal performance range for ionomer content, with systems containing 12 to 24 oligomers (20–30 % w/w) exhibiting superior water diffusion within Vulcan Carbon (VC) structures. By shedding light on water transport phenomena in PEMFCs, our findings contribute to a better understanding of fuel cell performance and provide valuable insights for the design and optimization of fuel cell systems.