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Chen Y, Wippermann K, Rodenbücher C, Suo Y, Korte C. Impedance Analysis of Capacitive and Faradaic Processes in the Pt/[Dema][TfO] Interface. ACS APPLIED MATERIALS & INTERFACES 2024; 16:5278-5285. [PMID: 38247120 PMCID: PMC10835653 DOI: 10.1021/acsami.3c15465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2024]
Abstract
The electrochemical reaction kinetics, especially the oxygen reduction reaction (ORR) at the cathode, is crucial for the performance of a fuel cell. In this study, the electrochemical processes on a polycrystalline Pt electrode in the presence of protic ionic liquid (PIL) electrolyte diethylmethylammonium triflate [Dema][TfO] are investigated by means of cyclic voltammetry and electrochemical impedance spectroscopy. Since water is continually produced during fuel cell operation, the effect of the water content in the PIL has been intensively analyzed. In order to reveal the dependence of the interfacial reaction characteristics on the electrode potential, the impedance spectra were simulated by an equivalent circuit whose parameters can be related to both Faradaic and capacitive processes. Two interfacial resistances were identified, which differ by about 3 orders of magnitude. The larger one is a charge transfer resistance that can be associated with slow Faradaic processes like the ORR and platinum oxidation/oxide reduction. The smaller resistance is probably linked with fast processes that involve water molecules, such as hydrogen deposition and oxidation. The high- and midfrequency capacitive processes are attributed to "classical" double layer and pseudocapacitive behavior, similar to those identified under nitrogen atmosphere.
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Affiliation(s)
- Yingzhen Chen
- Institute of Energy and Climate Research─Electrochemical Process Engineering (IEK-14), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
- RWTH Aachen University, 52062 Aachen, Germany
| | - Klaus Wippermann
- Institute of Energy and Climate Research─Electrochemical Process Engineering (IEK-14), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Christian Rodenbücher
- Institute of Energy and Climate Research─Electrochemical Process Engineering (IEK-14), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Yanpeng Suo
- Institute of Energy and Climate Research─Electrochemical Process Engineering (IEK-14), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
- RWTH Aachen University, 52062 Aachen, Germany
| | - Carsten Korte
- Institute of Energy and Climate Research─Electrochemical Process Engineering (IEK-14), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
- RWTH Aachen University, 52062 Aachen, Germany
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Hausen F. Relaxation Times of Ionic Liquids under Electrochemical Conditions Probed by Friction Force Microscopy. SMALL METHODS 2023; 7:e2300250. [PMID: 37551063 DOI: 10.1002/smtd.202300250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2023] [Revised: 07/14/2023] [Indexed: 08/09/2023]
Abstract
Ionic liquids (ILs) represent an important class of liquids considered for a broad range of applications such as lubrication, catalysis, or as electrolytes in batteries. It is well-known that in the case of charged surfaces, ILs form a pronounced layer structure that can be easily triggered by an externally applied electrode potential. Information about the time required to form a stable interface under varying electrode potentials is of utmost importance in many applications. For the first time, probing of relaxation times of ILs by friction force microscopy is demonstrated. The friction force is extremely sensitive to even subtle changes in the interfacial configuration of ILs. Various relaxation processes with different time scales are observed. A significant difference dependent on the direction of switching the applied potential, i.e., from a more cation-rich to a more anion-rich interface or vice versa, is found. Furthermore, variations in height immediately after the potential step and the presence of trace amounts of water are discussed as well.
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Affiliation(s)
- Florian Hausen
- Forschungszentrum Jülich, Institute of Energy and Climate Research, IEK-9, 52425, Jülich, Germany
- RWTH Aachen University, Institute of Physical Chemistry, 52074, Aachen, Germany
- INM-Leibniz Institute for New Materials, Campus D2 2, 66123, Saarbrücken, Germany
- Jülich-Aachen Research Alliance, Section: JARA-Energy, 52425, Jülich, Germany
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Wang T, Li L, Zhang F, Dai Z, Shah FU, Wang W, Xu F, An R. Microstructural probing of phosphonium-based ionic liquids on a gold electrode using colloid probe AFM. Phys Chem Chem Phys 2022; 24:25411-25419. [PMID: 36250344 DOI: 10.1039/d2cp02489f] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Atomic force microscopy (AFM) with a gold colloid probe modeled as the electrode surface is employed to directly capture the contact resonance frequency of two phosphonium-based ionic liquids (ILs) containing a common anion [BScB]- and differently lengthened cations ([P6,6,6,14]+ and [P4,4,4,8]+). The comparative interfacial studies are performed by creating IL films on the surface of gold, followed by measuring the wettability, thickness of the films, adhesion forces, surface morphology and AFM-probed contact resonance frequency. In addition, the cyclic voltammetry and impedance spectroscopy measurements of the neat ILs are measured on the surface of the gold electrode. The IL with longer cation alkyl chains exhibits a well-defined thin film on the electrode surface and enhanced the capacitance than the shorter chain IL. The AFM contact resonance frequency and force curves reveal that the longer IL prefers to form stiffer ion layers at the gold electrode surface, suggesting the "…anion-anion-cation-cation…" bilayer structure, in contrast, the shorter-chain IL forms the softer cation-anion alternating structure, i.e., "…anion-cation-anion-cation…".
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Affiliation(s)
- Tiantian Wang
- School of Materials Science and Engineering/Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology, Nanjing, 210094, China.
| | - Licheng Li
- Innovation Research Center of Lignocellulosic Functional Materials, College of Chemical Engineering, Nanjing Forestry University, Nanjing, 210037, China
| | - Fan Zhang
- Department of Engineering and Design, School of Engineering and Information, University of Sussex, Brighton, BN1 9RH, UK
| | - Zhongyang Dai
- High Performance Computing Department, National Supercomputing Center in Shenzhen, Shenzhen, 518055, China
| | - Faiz Ullah Shah
- Chemistry of Interfaces, Luleå University of Technology, 97187, Luleå, Sweden
| | - Wen Wang
- Zhongnong Guoke Planning and Design Co., Ltd, Nanjing, 210014, China
| | - Feng Xu
- School of Materials Science and Engineering/Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology, Nanjing, 210094, China.
| | - Rong An
- School of Materials Science and Engineering/Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology, Nanjing, 210094, China.
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