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| Home > Publications database > Interfaces between Catalytic Electrodes and Protic Ionic Liquids for the Intermediate-Temperature Polymer Electrolyte Fuel Cell |
| Abstract | FZJ-2020-01989 |
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2020
Abstract: Interfaces between catalytic electrodes and protic ionic liquids for the intermediate-temperature polymer electrolyte fuel cellsY. Chen, Jülich/DE, C. Rodenbücher, Jülich/DE, J. Giffin, Jülich/DE, K. Wippermann, Jülich/DE, C. Korte, Jülich/DEForschungszentrum Jülich GmbH, Institute of Energy and Climate Research (IEK-14), 52425 Jülich, GermanyWith the environmental concerns and energy issues, the demand for clean and sustain-able energy sources has become one of the most challenging topics in the current cen-tury. Fuel cells have stimulated particular interest, because they can generate electricity with high efficiency using “green hydrogen”. In recent years, polymer electrolyte mem-brane fuel cells (PEMFC) have turned out to be the most viable alternative to combus-tion engines for automotive applications. However, PEMFC with sulfonated fluoropoly-mers, e.g. NAFION®, whose proton conduction relies on the presence of water, limits the operating temperature below 80 °C (ambient pressure). A PEMFC operating at 100–120 °C would be more attractive, owing to a much more simplified system setup for water and heat management. This requires a novel non-aqueous electrolyte.In this study we investigate proton conducting ionic liquids (PIL) as alternative proton-conducting electrolytes for intermediate-temperature PEMFCs. Ionic liquids consist basically of bulky organic cations and anions of superacids. Due to the low lattice energy they are liquids at room temperature. A large variety of combination of cation and anion gives the opportunity to design ionic liquids with desired properties. The structure of the electrical double layer close to the electrode/electrolyte interface is completely different compared to classical aqueous solutions as there are alternating layers of cations and anions. Preceding investigations on PILs with cations of different Brønsted-acidity give rise to the assumption that the proton transfer from the cation to the active centres on the electrode surface is mainly determining the rate of the ORR. [1] As residual water is unavoidable during fuel cell operation even above 100 °C, its concentration and the acidity of the PIL will play an important role.In order to understand the electrochemical kinetics at the electrode-electrolyte inter-face, spectroelectrochemical analyses were carried out by combining cyclovoltammetry and impedance spectroscopy with FT-IR spectroscopy and atomic force microscopy (AFM). First results show that the structure of the electrical double layer and the ionic transport depend on the applied cell potential, the content of water and the temperature. The observed formation of a dense layered structure at the interface can be related to the interplay of Coulomb interaction between the ions and steric effects. The findings provide a better understanding of the electrochemical kinetics of protic ionic liquids at the catalytic surface and give valuable guidance for design and further optimization of ionic liquids for intermediate-temperature PEMFC fuel cells.[1] K. Wippermann, J. Wackerl, W. Lehnert, B. Huber and C. Korte, J. Electrochem. Soc., 2016, 163, F25.
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