Molecular insights into water penetration behavior in ionomer films for proton exchange membrane electrolysis cells

Q Chen and LH Fan and AX Ran and K Jiao, INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, 253, 127582 (2025).

DOI: 10.1016/j.ijheatmasstransfer.2025.127582

Water transport to catalysts in the anode catalyst layers of proton exchange membrane electrolysis cells is significant for electrolysis efficiency. Herein, this work employs all-atom molecular dynamics simulations to investigate the water penetration behavior and ionomer film structure on catalysts. The simulated results reveal that the ionomer film on the catalyst surface has a multilayered structure. The film structure on the iridium oxide (IrO2) catalyst surface is looser than that on the iridium (Ir) catalyst surface, due to the weaker interactions between IrO2 and ionomer. The film has a two-layer configuration when it is thinner, while a three-layer configuration when it thickens. When the water penetrates the ionomer films, the water clusters in the middle of ionomer films swell. Two water penetration mechanisms are identified. Water penetration is through the narrow water channels between the upper water layer and the water clusters for Ir catalysts, while through the broader wedge-shaped water channels between the upper water layer and the water clusters for IrO2 catalysts.

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