The Formation and Role of Oxide Layers on Pt during Hydrazine Oxidation in Protic Ionic Liquids

Walsh, Darren A.; Ejigu, Andinet; Muhammad, Sayyar; Licence, Peter

doi:10.1002/celc.201300111

Cited by 18 publications

(27 citation statements)

References 40 publications

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“…In our study, the displacement current that flowed at low potentials was likely due to the removal of adsorbed H (see Figure 2B), releasing protons that may have been accommodated by the ionic liquid anion yielding the free TfOH acid. The displacement current that flowed at potentials ≥ 0.281 V could represent loss of oxide ions from the surface (we recently showed that adsorbed oxide species form in these PILs due to trace water dissociation 42 Figure 1A and 1B) suggesting that the anions desorbing at the potentials on the right hand side of Figure 5B were also predominantly [TfO]anions rather than oxide anions. 49 We also note that the same authors speculated that the hydrophobic nature of Given the important role that ion adsorption appears to play during electrocatalysis in ionic liquids, it will be interesting to explore the structure sensitivity of such processes and the impact of such phenomena on electrocatalysis.…”

Section: Displacement Of Ions From Electrodes By Co the Potential Ofmentioning

confidence: 94%

The Role of Adsorbed Ions during Electrocatalysis in Ionic Liquids

Ejigu

Walsh

2014

J. Phys. Chem. C

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The effects of electrode-adsorbate interactions on electrocatalysis at Pt in ionic liquids are described. The ionic liquids are diethylmethylammonium trifluoromethanesulfonate, [dema][TfO], dimethylethylammonium trifluoromethanesulfonate, [dmea][TfO], and diethylmethylammonium bis(trifluoromethanesulfonyl)imide, [dema][Tf 2 N]. Electrochemical analysis indicates that a monolayer of hydrogen adsorbs onto Pt during potential cycling in [dema][[TfO] and [dmea][TfO]. In addition, a pre-peak is observed at lower potentials than that of the main oxidation peak during CO oxidation in the [TfO]-based liquids. In contrast, hydrogen does not adsorb onto Pt during potential cycling in [dema][Tf 2 N] and no pre-peak is observed during CO oxidation. By displacing adsorbed ions on Pt surfaces with CO at a range of potentials, and measuring the charge passed during ion displacement, the potentials of zero total charge of Pt in [dema][TfO] and [dmea][TfO] were measured as 271 ± 9 mV and 289 ± 10 mV vs. RHE, respectively. CO displacement experiments also indicate that the [Tf 2 N]ion is bound to the Pt surface at potentials above-0.2 V and the implications of ion adsorption on electrocatalysis of the CO oxidation reaction and O 2 reduction reaction in the protic ionic liquids are discussed.

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Section: Displacement Of Ions From Electrodes By Co the Potential Ofmentioning

confidence: 94%

The Role of Adsorbed Ions during Electrocatalysis in Ionic Liquids

Ejigu

Walsh

2014

J. Phys. Chem. C

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“…The asymptotic value of about 530 μC cm −2 can be interpreted as a monolayer of Pt oxide, where a theoretical charge of 440 μC cm −2 would be expected if only PtO would form. 43 At very low water contents (< 2 wt%), the PtO x reduction charge drops steeply down to a theoretical value of zero if the ionic liquid is anhydrous. As can be seen in Fig.…”

Section: Onset Potential Of Pt Oxidation / Charge Of Pto X Reduction-inmentioning

confidence: 98%

“…This result suggests further growth of the oxide film, exceeding one monolayer. Walsh et al 43 studied the system Pt / [Dema][TfO] and found multiple layers of oxides at elevated temperatures. Unlike our own measurements, these multilayers were observed even at trace water contents of 240 ppm; however, at a much higher potential limit of 2 V (in this work: 1.6 V).…”

Section: Influence Of the Water Content On A [Demamentioning

confidence: 99%

“…In a second publication, Walsh et al investigated the formation of Pt oxides in ionic liquids via trace water oxidation, taking the hydrazine oxidation reaction as a probe of the reactivity of the Pt oxide layers. 43 According to the findings of Walsh et al, multiple layers of oxide form at elevated temperatures and potentials. The strong effect of temperature on the thickness of the Pt oxide layers corresponds to the results of our recent z E-mail: k.wippermann@fz-juelich.…”

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confidence: 99%

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In Situ Determination of the Water Content of Ionic Liquids

Wippermann

Giffin

Korte

2018

J. Electrochem. Soc.

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This study examines the applicability of electrochemical methods to the in situ determination of the water content in proton-conducting ionic liquids (PILs). Two proton-conducting ionic liquids with different acidities and hygroscopicities of the cations, sulfoethylmethylammonium trifluoromethanesulfonate, [2-Sema][TfO] and N,N-diethylmethylammonium trifluoromethanesulfonate, [Dema][TfO], were used. At first, PIL water electrolytes with known water concentrations ([2-Sema][TfO]: 0.64-6.1 wt%, [Dema][TfO]: 0.18-99.5 wt%) were prepared. Then, the influence of the water content on the electrochemical properties, namely the electrical conductivity, charge of hydrogen oxidation, charge of Pt oxide reduction and onset potential of Pt oxidation, were investigated. The four parameters were plotted as a function of the water concentration and fitted by exponential, linear or asymptotic functions. These fits serve as calibration curves that can be used to determine the actual water concentration by measuring one or more of the four parameters investigated. It was found that the measurement of specific ion conductivity is a fast and simple method across a wide range of water concentrations. The evaluation of the Pt oxide reduction charge from cyclic voltammograms is more time-consuming, but provides higher accuracy at low water concentrations, although the accuracy also depends on the nature of the ionic liquid.

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“…As shown in the inset of Figure 4(A), an oxidation wave at an onset potential 0.95 V with peak potential at 1.02 V at Pt and at an 1.2 V having peak potential 1.5 V at Au electrodes versus Ag wire. These oxidation currents corresponds to adsorption and oxidation of trace water present in TEAS (1.43 w/w %) forming Pt-OH/PtO and AuO/Au 2 O 3 at Pt and Au, respectively [30,31]. If we scan the potential of the electrode further beyond the switching potentials, the current due to reductive and oxidative decomposition of the PIL will drastically increase so that all the ionic liquid decompose to another product.…”

Section: Electrochemical Characterization Of Teasmentioning

confidence: 99%

Synthesis, characterization and electrochemistry of triethyl ammonium sulphate ionic liquid

Khan

Muhammad

Shah

et al. 2020

Zeitschrift Für Physikalische Chemie

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Protic ionic liquids (PILs) being intrinsic proton conducting ionic species are considered as potential green electrolytes for study of electrocatalytic reactions and for fabrication of IL-based fuel cells (FCs) and batteries. We have prepared a sulfate anion based protic ionic liquid (PIL), triethylammonium sulfate (TEAS) through a reaction involving transfer of proton from H2SO4 to triethylamine (TEA). 1H NMR and FT-IR spectroscopic techniques were employed for confirmation of the synthesis of TEAS and water content of the PIL was quantified using coulometric Karl–Fischer (KF) titration. 1H NMR and FT-IR analysis confirm the synthesis of the PILs and KF-titration analysis shows that TEAS contains 1.43 w/w % water. Electrical conductivity of TEAS was determined at different temperatures showing that the PIL has excellent ionic conductivity that enhances with rise in temperature of the medium. The temperature dependence of the conductivity of the PIL follows the Arrhenius equation as the logσ versus 1/T plot is linear. The electrochemical windows (EWs) of the electrolyte were found using cyclic voltammetry at Pt and Au working electrodes and found to decrease with increase in temperature of the medium. The data revealed that the surfaces of the electrodes are covered with oxide layers due to oxidation of trace water (1.43 w/w %) present in the PIL. The oxide layers growth increase and their onset potential moves to less positive values as the temperature of the PILs is increased. The data was compared with the literature and would be helpful in understanding of the surface electrochemistry in this neoteric medium for being used as potential electrolyte in industry for various electrochemical applications.

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The Formation and Role of Oxide Layers on Pt during Hydrazine Oxidation in Protic Ionic Liquids

Cited by 18 publications

References 40 publications

The Role of Adsorbed Ions during Electrocatalysis in Ionic Liquids

The Role of Adsorbed Ions during Electrocatalysis in Ionic Liquids

In Situ Determination of the Water Content of Ionic Liquids

Synthesis, characterization and electrochemistry of triethyl ammonium sulphate ionic liquid

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