Kinetics and mechanism of oxygen reduction in a protic ionic liquid

Walsh, Darren A.; Ejigu, Andinet; Smith, Joshua J.; Licence, Peter

doi:10.1039/c3cp44669g

Cited by 43 publications

(53 citation statements)

References 48 publications

(61 reference statements)

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“…It is found that the resistance modulation rate is approximately one order higher than that under dry N 2 in lateral gating geometry. This is consistent with the observation that water or protons can serve as catalysts to facilitate the oxygen reduction reaction process in IL 54,55 .…”

Section: Resultssupporting

confidence: 92%

A correlated nickelate synaptic transistor

et al. 2013

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Inspired by biological neural systems, neuromorphic devices may open up new computing paradigms to explore cognition, learning and limits of parallel computation. Here we report the demonstration of a synaptic transistor with SmNiO 3 , a correlated electron system with insulator-metal transition temperature at 130°C in bulk form. Non-volatile resistance and synaptic multilevel analogue states are demonstrated by control over composition in ionic liquid-gated devices on silicon platforms. The extent of the resistance modulation can be dramatically controlled by the film microstructure. By simulating the time difference between postneuron and preneuron spikes as the input parameter of a gate bias voltage pulse, synaptic spike-timing-dependent plasticity learning behaviour is realized. The extreme sensitivity of electrical properties to defects in correlated oxides may make them a particularly suitable class of materials to realize artificial biological circuits that can be operated at and above room temperature and seamlessly integrated into conventional electronic circuits.

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Section: Resultssupporting

confidence: 92%

A correlated nickelate synaptic transistor

et al. 2013

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“…82 Only in the case of a significant addition of impurities, e.g. 10 −3 M H 3 PO 3 , does the oxygen reduction mainly proceed via an indirect 2-electron mechanism with hydrogen peroxide as product.…”

Section: Resultsmentioning

confidence: 99%

2-Sulfoethylammonium Trifluoromethanesulfonate as an Ionic Liquid for High Temperature PEM Fuel Cells

Wippermann

Wackerl

Lehnert

et al. 2015

J. Electrochem. Soc.

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Tafel Oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFC).-High temperature polymer electrolyte fuel cells (HT-PEFCs) are currently based on phosphoric acid-doped polybenzimidazole-type membranes (PBI) and are operated in a temperature range of 120-180• C. HT-PEFCs have several advantages over low temperature PEFCs, such as: easier water and heat management, the possibility of recovering high-grade waste heat, a more compact cooling system and a higher CO tolerance by the anode catalyst.However, a major drawback of HT-PEFCs is the sluggish oxygen reduction reaction (ORR) kinetics in the presence of phosphoric acid. This is primarily caused by three effects: (i) The inhibition effect of phosphoric acid on the ORR because of the poisoning of the Pt catalyst due to the adsorption of the H 3 PO 4 species onto active catalyst sites. (ii) The low solubility of oxygen in phosphoric acid. (iii) The slow diffusion of oxygen through the film of phosphoric acid which covers the platinum catalyst.The adsorption of phosphate by platinum has been studied for more than 30 years 1-15 by means of cyclic voltammetry (CV), [2][3][4][5]9,[11][12][13][14][16][17][18][19][20][21] rotating disc electrode measurements (RDE), [2][3][4][5]8,9,11,13,14 electrochemical impedance spectroscopy (EIS), 13,16,22 transient measurements, 9,23,24 Fourier transform infrared spectroscopy (FTIR), 20,25-27 electrochemical quartz crystal microbalance (QCM), 18 radio tracer experiments, 28 X-ray photoelectron spectroscopy (XPS) 17 and X-ray absorption spectroscopy (XAS). 14,15 The in-operando XAS measurements recently published by Kaserer et al. show the adsorption behavior of H 3 PO 4 species on Pt/C fuel cell cathode catalysts in the temperature range of 50-170• C under the operating conditions of an HT-PEFC. 15In diluted aqueous solutions and at moderate temperatures, sulphuric acid and sulfonic acids like methanesulfonic acid (MSA) or trifluoromethanesulfonic acid (triflic acid, TFMSA) have been found to be less poisonous than phosphoric acid because sulfonate groups are less strongly adsorbed on Pt. 3,29,30 For example, Zelenay et al.,29 in a comparative study of phosphoric acid and TFMSA, showed that * Electrochemical Society Active Member. z E-mail: k.wippermann@fz-juelich.de 0.02 M TFMSA is indeed less strongly adsorbed by comparison to 0.02 M phosphoric acid at room temperature. However, the free space available for oxygen reduction is found to be similar at elevated temperatures and for concentrated solutions. 29 Under these conditions, the advantage of TFMSA lies in its higher oxygen solubility and diffusivity rather than its poisoning effect. 29 Although this result cannot be generalized, it still indicates the importance of oxygen solubility and the diffusion coefficient of oxygen in the electrolyte being used. Proton conducting ionic liquids (PIL).-With respect to alternative electrolytes for HT-PEFCs, proton-conducting ionic liquids (PILs) appear to be suitable, as they do not rely on solvents like water. Moreover...

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“…While the observation of a relatively-fast HOR rate at Pt in PILs is encouraging for the developing of devices such as PIL-based H 2 fuel cells, it is notable that the O 2 reduction reaction in PILs is more complicated and slower. 43,56 It is our opinion that detailed kinetic analyses such as that described herein will help not only with the development and discovery of new, high-performance electrocatalysts for use in such media but will also aid in understanding the fundamental electrochemistry of these novel media. …”

Section: Hor Electrooxidation In [Demamentioning

confidence: 98%

Hydrogen Electrooxidation under Conditions of High Mass Transport in Room-Temperature Ionic Liquids and the Role of Underpotential-Deposited Hydrogen

Goodwin

Walsh

2016

J. Phys. Chem. C

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. (2016) Hydrogen electrooxidation under conditions of high mass transport in room-temperature ionic liquids and the role of underpotential-deposited hydrogen. Journal of Physical Chemistry C, 120 (21). pp. 11498-11507. ISSN 1932-7455 Access from the University of Nottingham repository: http://eprints.nottingham.ac.uk/33911/1/Article%20jp-2016-01592f.R2.pdf Copyright and reuse:The Nottingham ePrints service makes this work by researchers of the University of Nottingham available open access under the following conditions. This article is made available under the University of Nottingham End User licence and may be reused according to the conditions of the licence. For more details see: http://eprints.nottingham.ac.uk/end_user_agreement.pdf A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription. AbstractThe hydrogen oxidation reaction (HOR), an electrocatalytic reaction of fundamental and applied interest, was studied in the protic ionic liquid (PIL) diethylmethylammonium trifluoromethanesulfonate, [dema][TfO], at Pt electrodes using rotating disk electrode (RDE) and ultramicroelectrode (UME) voltammetry. A steady-state HOR current is observed during RDE voltammetry at overpotentials > 50 mV but an additional plateau is observed in the overpotential region 50-200 mV when using UMEs. The difference in voltammetric responses is attributed to higher rate of mass transport to the UME than to the RDE. Three models have been used to fit the experimental data. The first is a dual-pathway model, which assumes that the Tafel-Volmer and Heyrovsky-Volmer pathways are both active over the potential range of interest and no blockage of catalytic sites occurs during the reaction. The second is a dual-pathway model, which assumes that reaction intermediates block access of H 2 to catalytic sites. The third is based on the premise that underpotential-deposited hydrogen atoms (H upd ) can block adsorption and electrooxidation of H 2 at the Pt surface. While each model fits the polarisation curves reasonably well, detailed analysis suggests that the H updblocking model describes the responses better. To the best of our knowledge, this work is the first to demonstrate the advantages of UME voltammetry over RDE voltammetry for studying electrocatalytic reactions in PILs, and the first to show that H upd can inhibit an electrocatalytic reactions in an ionic liquid, a factor that may become important as the technological applications of these liquids increase.3

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Kinetics and mechanism of oxygen reduction in a protic ionic liquid

Cited by 43 publications

References 48 publications

A correlated nickelate synaptic transistor

A correlated nickelate synaptic transistor

2-Sulfoethylammonium Trifluoromethanesulfonate as an Ionic Liquid for High Temperature PEM Fuel Cells

Hydrogen Electrooxidation under Conditions of High Mass Transport in Room-Temperature Ionic Liquids and the Role of Underpotential-Deposited Hydrogen

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