Insights into H2 and O2 transport in the three-phase boundary of PEM fuel cells

Abstract

Proton Exchange Membrane Fuel Cells (PEMFCs) are a promising sustainable energy technology characterized by high efficiency and low emissions. Their performance is significantly influenced by the Three-Phase Boundary (TPB) where the electrolyte, catalyst, and reactant gasses converge. This study builds on our previous work by investigating the transport properties of hydrogen and oxygen in PEMFCs, focusing on the impact of the Nafion content and membrane hydration. Using molecular dynamics simulations, we analyzed the gas transport in a system of Pt nanoparticles supported on Vulcan Carbon with varying Nafion hydration levels. A high-pressure setup was employed to evaluate gas density, diffusion coefficient, solubility, and permeability. Our results show that the gas density increases at the Pt-Nafion interface but decreases with Nafion concentrations above 24 oligomers, affecting diffusion and permeability. The diffusion coefficients of hydrogen were higher than those of oxygen, which can be attributed to the smaller size of hydrogen and weaker interactions between hydrogen and Nafion. In addition, a Morse potential model for hydrogen adsorption on Pt surfaces was developed, which aligns with the experimental data. These findings highlight the critical role of the Nafion content in the gas transport properties, suggesting that optimizing the Nafion concentration is essential for enhancing the PEMFC efficiency.