The limits of the analogy between boiling and gas evolution at electrodes

Vogt, Helmut; Aras, Ömür; Balzer, R.

doi:10.1016/j.ijheatmasstransfer.2003.07.023

Cited by 77 publications

(49 citation statements)

References 22 publications

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“…At first sight this is surprising; the field was expected to create a transverse flow which tends to dislodge the bubble, especially at high current density. The opposite is observed; the bubble radius in the applied field approaches that expected for release governed by upthrust [27]. Data (not shown here) in a vertical field with a horizontal microelectrode surface confirm the trend (a reduction in bubble release frequency from 5 Hz in zero field to 0.5 Hz in 5T).…”

Section: Page 15 Of 36supporting

confidence: 69%

“…It should be noted that this is much greater than the upthrust given by Archimedes principle, Vg = 0.03 N. The radius of the bubble when the upthrust balances the surface tension is about 300 m [27]. Convective forces must be at play to sweep off the bubble, even in the absence of a magnetic field.…”

Section: Discussionmentioning

confidence: 91%

“…Matsushima uses a lower value(~0.25 A cm -2 ), but the critical radius for a stable nucleus is reported strongly dependent on current density by Vogt [27] Page 11 of 36…”

Section: Noise Spectramentioning

confidence: 99%

See 2 more Smart Citations

Influence of magnetic field on hydrogen reduction and co-reduction in the Cu/CuSO4 system

Fernández¹,

Diao²,

Dunne³

et al. 2010

Electrochimica Acta

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Section: Page 15 Of 36supporting

confidence: 69%

Section: Discussionmentioning

confidence: 91%

See 1 more Smart Citation

Influence of magnetic field on hydrogen reduction and co-reduction in the Cu/CuSO4 system

Fernández¹,

Diao²,

Dunne³

et al. 2010

Electrochimica Acta

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“…Bubble nucleation is highly dependent on the local properties of the surface, with pits and hydrophobic surfaces encouraging nucleation. 18,19 However, we desired to decouple the sites of preferred bubble formation from the sites of enhanced gas evolution. Without introducing artificial nucleation sites nearby, it was necessary to use strong local irradiation to overcome the diffusion of dissolved gases into the bulk electrolyte and achieve the local supersaturation necessary to form a bubble.…”

Section: Discussionmentioning

confidence: 99%

Water-Splitting Photoelectrolysis Reaction Rate via Microscopic Imaging of Evolved Oxygen Bubbles

Leenheer

Atwater

2010

J. Electrochem. Soc.

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Bubble formation and growth on a water-splitting semiconductor photoelectrode under illumination with above-bandgap radiation provide a direct measurement of the gas-evolving reaction rate. Optical microscopy was used to record the bubble growth on single-crystal strontium titanate immersed in basic aqueous electrolyte and illuminated with UV light at 351/364 nm from a focused argon laser. By analyzing the bubble size as a function of time, the water-splitting reaction rate was determined for varying light intensities and was compared to photocurrent measurements. Bubble nucleation was explored on an illuminated flat surface, as well as the subsequent light scattering and electrode shielding due to the bubble. This technique allows a quantitative examination of the actual gas evolution rate during photoelectrochemical water splitting, independent of current measurements. © 2010 The Electrochemical Society. ͓DOI: 10.1149/1.3462997͔ All rights reserved. The production of hydrogen using solar energy to directly split water in a semiconductor photoelectrochemical cell is a promising source of carbon-free fuel, 1 but many issues with the semiconductor-liquid interface remain. Semiconductors with bandgaps ϳ2 eV useful for absorbing the solar flux and possessing the necessary potential to split water 2 often suffer stability issues due to photoexcited charge carriers corroding the semiconductor rather than transferring into the electrolyte.3 Adding heterogeneous catalysts or structuring the electrode surface can provide more active sites for charge transfer, lowering the overpotentials required and possibly increasing stability, but often the nature of the active sites is unknown.4-9 Traditional experimental techniques involve modifying or structuring the entire surface of a semiconductor photoelectrode and measuring the photocurrent under illumination; this method provides only the average reaction rate of all the various redox reactions occurring over the entire exposed surface. Localized methods that differentiate the activity on separate patterned areas on the same electrode could offer a wealth of information about the surface sites important for efficient charge transfer. Previous research has focused on utilizing a scanned electrochemical probe near the surface 10 that can even include local illumination through an optical fiber, 11 a very useful but rather perturbative and difficult method to implement.Examining the evolved gas bubbles could provide this type of local measurement by recording their growth rate at different surface features. Additionally, measuring the bubble and hence the actual gas produced differentiates between the gas-evolving reaction of interest and any parasitic corrosion reactions that can still contribute to the measured current. Optical microscopy of the photogenerated gas bubbles during their growth is a straightforward technique and provides a localized measurement of the reaction rate at various areas on a semiconductor surface.As a model system to explore the use of this technique...

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“…The macroscopic performances are local gas concentration dependent, with a strong coupling with hydrodynamic and electric properties; but the gas volume shape and size are dependent of bubble scale properties, but also of the local hydrodynamic shear stress. The bubble formation during electrochemical processes and its electrochemical cell scale consequences is a few investigated fields [1][2][3][4][5][6][7], whereas the same topic has been intensively explored for heat transfer science or gas injection through porous walls for turbulence promotion and transfer increase [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Two-phase electrolysis process modelling: from the bubble to the electrochemical cell scale

Mandin¹,

Roustan²,

Wüthrich³

et al. 2007

WIT Transactions on Engineering Sciences, Vol 54

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During two-phase electrolysis for hydrogen, aluminium or fluor production, there are bubbles which are created at electrodes which imply a great hydrodynamic acceleration but also quite important electrical properties and electrochemical processes disturbance. There are few works concerning the local modelling of electrochemical processes during a two-phase electrolysis process. Nevertheless, effects like the anode effect, particularly expensive on the point of the process efficiency, should need a better understanding. The goal of the present work is to present the modelling and the numerical simulation of the gas production, from the single bubble scale to the macroscopic electrochemical cell, during the two-phase electrolysis process. Bubbles are motion sources for the electrolysis cell flow, and then hydrodynamic properties are strongly coupled with species transport and electrical performances. The presence of bubbles modifies these global and local properties: the electrolysis cell and the current density distribution are modified. The present work shows theoretical modelling on both scales and also performance changes during the two-phase electrolysis processes.

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The limits of the analogy between boiling and gas evolution at electrodes

Cited by 77 publications

References 22 publications

Influence of magnetic field on hydrogen reduction and co-reduction in the Cu/CuSO4 system

Influence of magnetic field on hydrogen reduction and co-reduction in the Cu/CuSO4 system

Water-Splitting Photoelectrolysis Reaction Rate via Microscopic Imaging of Evolved Oxygen Bubbles

Two-phase electrolysis process modelling: from the bubble to the electrochemical cell scale

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