Effects of protic ionic liquids on the oxygen reduction reaction – a key issue in the development of intermediate-temperature polymer-electrolyte fuel cells

Wippermann, Klaus; Korte, Carsten

doi:10.1016/j.coelec.2021.100894

Cited by 12 publications

(8 citation statements)

References 44 publications

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“…The ORR performance is dominated by the electron and proton transfer to the adsorbed O 2 molecule on the Pt electrode. 4 In the case of the neat PIL, the protic cation serves as a proton donor in the rate-determining step. If water is added, the protolysis equilibrium BH + + H 2 O ⇌ B + H 3 O + is established and results in the formation of H 3 O + , which acts as the dominating proton donor in the ORR kinetics.…”

Section: Analysis Of Fitting Resultsmentioning

confidence: 99%

“…The onset potential of the ORR is found at about 0.2 V. As the potential goes from 0.2 to −0.2 V, the kinetic resistance of neat [Dema][TfO] drops from 4.32 ± 0.04 to 1.200 ± 0.004 kΩ·cm 2 . The ORR performance is dominated by the electron and proton transfer to the adsorbed O 2 molecule on the Pt electrode . In the case of the neat PIL, the protic cation serves as a proton donor in the rate-determining step.…”

Section: Resultsmentioning

confidence: 99%

“…Another growing field of application is as novel electrolytes in electrochemical devices due to their wide electrochemical windows and good ionic conductivity. Recently, protic ionic liquids (PILs) immobilized in a host polymer have been considered as potential electrolytes for proton exchange membrane fuel cells (PEMFCs) to enable atmospheric operation above 100 °C. − A prerequisite for the technical application of a PIL electrolyte in fuel cells is a detailed understanding of the electrochemical kinetics of fuel-cell-relevant electrode processes, like the oxygen reduction reaction (ORR) at the cathode and the hydrogen oxidation reaction (HOR) at the anode. Since the kinetics of the ORR is much slower than the HOR, the performance of a PEMFC relies primarily on the ORR, which is the limiting factor for the current density in a PEMFC.…”

Section: Introductionmentioning

confidence: 99%

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Impedance Analysis of Capacitive and Faradaic Processes in the Pt/[Dema][TfO] Interface

Chen,

Wippermann,

Rodenbücher

et al. 2024

ACS Appl. Mater. Interfaces

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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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Section: Analysis Of Fitting Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Impedance Analysis of Capacitive and Faradaic Processes in the Pt/[Dema][TfO] Interface

Chen,

Wippermann,

Rodenbücher

et al. 2024

ACS Appl. Mater. Interfaces

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“…Recent reviews have detailed applications of ILs in drug delivery, 17 biomedical fields, 18 compound recovery, 19 gas absorption, 20 nanoparticle synthesis and modification, 21 photonic materials, 22 lubricants, 23 metal deposition, 24 fuel cells, 25 and protein purification. 26 Fig.…”

Section: Ionic Liquid Applicationsmentioning

confidence: 99%

Progress in the applications of biocompatible ionic liquids: renewable commodity production, catalytic and pharmaceutical approaches – a review

Costa,

Forster-Carneiro,

Hallett

2024

Green Chem.

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“…The proton availability on the cation has been considered one of the most important effects on the ORR activity. Cations with different acidities (p K a ) were investigated and improvement in the onset potential of ORR has been observed in the order of increasing cation acidity. , The open-circuit potential of H 2 /O 2 is also reported to be related to Δp K a between the cations and anions. Either too high or too low Δp K a will decrease the ORR activity.…”

Section: Introductionmentioning

confidence: 99%

Revealing Interfacial Reactions on Pt Electrodes in Ionic Liquids by In Situ Fourier-Transform Infrared Spectroscopy

Chen,

Rodenbücher,

Wippermann

et al. 2023

Anal. Chem.

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In situ monitoring of the electrolyte/electrode interfacial processes, such as the oxygen reduction reaction (ORR), is crucial for the design of electrolytes for fuel cells. In this study, we investigate the electrochemical behavior of platinum electrodes in protic ionic liquids (PILs) by means of in situ Fourier-transform infrared spectroscopy coupled with cyclic voltammetry. The result provides direct evidence of the change of water at the Pt electrode surface due to Pt oxide formation and reduction. A decrease in the interfacial water was observed in the spectra upon the formation of the Pt oxide. Conversely, the local water concentration at the electrode surface increases if the Pt oxide is reduced and the ORR takes place. At the same time, more cations replace anions on the electrode. The ORR kinetics in the [TFSI]-based PILs is slower than in the [TfO]-based ones, which could result from a blockage of catalytic sites by the adsorbed [TFSI] anions. It suggests that reducing the anion adsorption on the platinum surface could provide an opportunity to enhance the ORR activity.

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Effects of protic ionic liquids on the oxygen reduction reaction – a key issue in the development of intermediate-temperature polymer-electrolyte fuel cells

Cited by 12 publications

References 44 publications

Impedance Analysis of Capacitive and Faradaic Processes in the Pt/[Dema][TfO] Interface

Impedance Analysis of Capacitive and Faradaic Processes in the Pt/[Dema][TfO] Interface

Progress in the applications of biocompatible ionic liquids: renewable commodity production, catalytic and pharmaceutical approaches – a review

Revealing Interfacial Reactions on Pt Electrodes in Ionic Liquids by In Situ Fourier-Transform Infrared Spectroscopy

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