Regensburg 2025 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 4: Solid-Liquid Interfaces: Structure

O 4.5: Vortrag

Montag, 17. März 2025, 11:30–11:45, H4

Elucidating the double layer structure of protic ionic liquid electrolytes for next-generation fuel cells — •Christian Rodenbücher, Yingzhen Chen, Federico Parisi, Piotr M. Kowalski, and Carsten Korte — Forschungszentrum Jülich GmbH, Institute of Energy Technologies (IET-3 & IET-4), 52425 Jülich, Germany

Polymer electrolyte membrane fuel cells (PEMFCs) are the backbone of a future hydrogen-based renewable energy system. Increasing their operation temperature to 100–160 ^∘C would allow for a simpler water management and the use of waste heat. In this temperature range, conventional proton conducting polymers such as Nafion are not applicable, since they rely on the presence of water. Hence, we study immidazolium-based protic ionic liquids, which provide a high thermal and chemical stability and a high proton conductivity. We present experimental investigations using impedance spectroscopy, infrared spectroscopy, and atomic force microscopy combined with atomistic simulations by molecular dynamics and density functional theory. Our results reveal that depending on the electrode charge, a dense layered structure of alternating anion and cation layers is formed. Upon the addition of water, which is naturally produced during fuel cell operation, the structuring becomes distorted resulting in the accumulation of water at the interface and the increase of the onset potential of the oxygen reduction reaction. Our findings illustrate that the kinetics of the fuel cell reactions is influenced not only by bulk properties of the electrolyte but also by the adsorption at the electrode, which may be tuned by designing ionic liquids with bespoke properties.

Keywords: Ionic liquids; Electrochemical double layer; Fuel Cells; Infrared spectroscopy; Atomic force microscopy