Optical Studies of Electrolyte Films on Gas Electrodes

Müller, Rolf

doi:10.1149/1.2424161

Cited by 22 publications

(9 citation statements)

References 15 publications

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“…14 With an alkaline electrolyte, interesting interfacial phenomena have been observed. [15][16][17][18][19][20][21] In a previous study, we observed an in situ meniscus motion during the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) on a platinum electrode. 17 A spread of the three-phase interface during the ORR was observed and the role of hydroxide ions in determining the surface tension was investigated.…”

mentioning

confidence: 99%

Observation of Three-Phase Interface during Hydrogen Electrode Reactions in Unitized Regenerative Fuel Cell

Majima

Matsushima

Fukunaka

et al. 2014

J. Electrochem. Soc.

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The dynamic behavior of the meniscus of a potassium hydroxide and sulfuric acid droplet on a platinum electrode was studied using a charge-coupled device (CCD) camera and confocal laser microscopy. The three-phase interface was investigated during the hydrogen oxidation reaction (HOR) and the hydrogen evolution reaction (HER). Contact angle measurements revealed a spreading interface during the HER whereas the droplet shape remained unchanged during the HOR for both droplets. The overhead view revealed the formation of many fine droplets near the meniscus boundary during the HOR in the alkaline electrolyte, which agrees with previous results for the oxygen reduction reaction (ORR). The correlation of these observations with electrochemical data and differences in the results between the HOR and the HER suggest that the motion of the meniscus was induced by local pH and temperature gradients, presumably caused by a non-uniform reaction because of the limitations of the dissolved gas. Hydrogen is an attractive energy source as an alternative to fossil fuels. [1][2][3][4] Hydrogen can be produced from water and used in fuel cells. No toxic gases are generated and thus energy shortages and environmental problems can be prevented. Unitized regenerative fuel cells (URFCs) are ideal energy devices.5-7 They function by generating electricity as fuel cells and they produce hydrogen gas by water electrolysis. They are compact and economic because common electrodes may be used. However, URFCs require highly controlled wettability and this is dependent on the operational mode. A hydrophobic nature is desired for the fuel cell mode and a hydrophilic is required for water electrolysis. Therefore, intrinsic interfacial properties make it difficult to improve the energy conversion efficiency.The complex interface consists of an electrode (solid), an electrolyte (liquid), and a gas (air) and this is referred to as the three-phase interface, which is an essential part of the relevant electrochemical reaction. The meniscus plays an important role in controlling the reaction rate. [8][9][10][11][12][13] Inaba et al. reported that the hydrogen oxidation reaction (HOR) was affected by the shape of the meniscus, which determines the diffusion path of the dissolved gas.14 With an alkaline electrolyte, interesting interfacial phenomena have been observed. [15][16][17][18][19][20][21] In a previous study, we observed an in situ meniscus motion during the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) on a platinum electrode. 17 A spread of the three-phase interface during the ORR was observed and the role of hydroxide ions in determining the surface tension was investigated.To clarify the mechanism of this dynamic motion, in this study we measured the contact angle using different electrolytes and gas atmosphere used in a previous study. The relationship between the wettability and the electrochemical reaction of the HOR and the hydrogen evolution reaction (HER) is thus discussed in detail. ExperimentalThe experi...

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mentioning

confidence: 99%

Observation of Three-Phase Interface during Hydrogen Electrode Reactions in Unitized Regenerative Fuel Cell

Majima

Matsushima

Fukunaka

et al. 2014

J. Electrochem. Soc.

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“…As determined quantitatively in the case of metal]gas electrodes in alkaline solutions (12,13), such films can extend over distances which exceed the meniscus height (a few mm) by several orders of magnitude. As determined quantitatively in the case of metal]gas electrodes in alkaline solutions (12,13), such films can extend over distances which exceed the meniscus height (a few mm) by several orders of magnitude.…”

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confidence: 89%

Polarization Effects on Meniscus Characteristics in Molten Carbonate

Matsumura

Selman

1992

J. Electrochem. Soc.

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Meniscus heights on a gold flag electrode partially submerged in Li/K carbonate (62/38 mole percent) at 650~ have been determined under a variety of O=-CO= gas mixtures at atmospheric pressure. The meniscus height as a function of electrode potential shows a characteristic minimum for each gas composition and a relatively steep increase with increasing cathodic polarization. Analysis of the near-equilibrium data, assuming electrocapillary effects only, shows that this is consistent with specific adsorption of oxide ion on the electrode. At appreciable polarization, mass-transfer effects as well as adsorption appear to play a role, and the approach to steady-state conditions following a disturbance is slow.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35 Downloaded on 2015-06-13 to IP

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“…For high-energy surfaces the ^"Potential or surface potential or contact potential will influence the surface tensions and hence 9 [397,440]. From the phenomena observed with model porous electrodes (mostly cylindrical capillaries), which we will not discuss here, it is clear that electrochemical processes occurring at the surface may result in an increase as well as a decrease of 9 (see [440][441][442][443][444]). Further, it is well known that the C-potential of mineral surfaces depends strongly on the pre-treatment of the surface and, m general, displays a time effect when aged in water [R445].…”

Section: 82 Liquid Penetrates Solid or Filmmentioning

confidence: 99%

“…Evaporation may further cause a change in film properties when there is more than one component present in the film. These effects can be compared with and could be aggravated by the Marangoni phenomena caused by preferential evaporation [452,453], temperature gradients [453,454] and electro-osmotic gradients [442,443,455]. Probably, thfe phenomena reported by Hardy [456] and Bangham [39 9,427], concerning the sensitivity of 9 to the presence of a second adsorbable compound, fall into this class.…”

Section: 84 De-or Replacement Of Adsorbed Filmsmentioning

confidence: 99%

Contact angle and film jumps

Brakel

Heertjes

1977

Nature

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The disjoining pressure 4.3 Indirect methods of calculating 9 4.3.1 Critical surface tension 4.3.2 Calculation from the work of adhesion 4.3.3 Calculation from adsorption isotherms 4.4 Contact angles on polystyrene 4.5 Contact angle glass-water 4.6 Contact angle glass-toluene/hexane 4.6.1 Introduction 4.6.2 Critical surface tension of glass 4.6.3 Autophobic liquids 4.6.4 Impurities 4.6.5 Calculation of 6 4.6.6 Non-duplex films 4.7 Possible mechanisms causing lib behaviour 4.7.1 Introduction 4.7.2 Increasing liquid surface tension 4.7.3 Decrease of effective meniscus circumference 4.8 Decreasing contact angles 100 4.8.1 General remarks 100 4.8.2 Liquid penetrates solid or film 101 4.8.3 Dissolving surface 4.8.4 De-or replacement of adsorbed films 4.8.5 Evaporation from the film 4.8.6 Film jumps 4.9 Interpretation lib behaviour 4.9.1 General remarks 4.9.2 Polystyrene 4.9.3 Glass-water 4.9.4 Glass -apolar liquids 4.10 Concluding remarks 104 5 CONCAVE AND ANTICLASTIC MENISCI 107 5

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Optical Studies of Electrolyte Films on Gas Electrodes

Cited by 22 publications

References 15 publications

Observation of Three-Phase Interface during Hydrogen Electrode Reactions in Unitized Regenerative Fuel Cell

Observation of Three-Phase Interface during Hydrogen Electrode Reactions in Unitized Regenerative Fuel Cell

Polarization Effects on Meniscus Characteristics in Molten Carbonate

Contact angle and film jumps

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