A population balance approach to the study of bubble behaviour at gas-evolving electrodes

Bryson, A.W.; Hofman, David Lester

doi:10.1007/bf01039401

Cited by 11 publications

(9 citation statements)

References 12 publications

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“…[10] has to be corrected by introducing the bubble efficiency. This procedure was used recently by several authors (42,50,51). This apparently contradicts the conclusion of Sedahmed (48) as to the use of Eq.…”

Section: Discussionmentioning

confidence: 87%

Ionic Mass Transfer of Zinc in Alkaline Solutions with Simultaneous Hydrogen Evolution

St‐Pierre

Piron

1992

J. Electrochem. Soc.

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Sherwood numbers were determined for mass transfer of zinc in alkaline solutions with coevolution of hydrogen (0.15-0.9 mmol/cm 3 ZnO + 8.4 mmol/cm 3 KOH, 300 K). The separation between the zinc and the hydrogen current was performed using polarization curves. The separation between Sherwood numbers due to natural and bubble convection was obtained by an additive law since hydrogen evolution took place only at current densities higher than the zinc limiting current density. It is shown that the contribution to mass transfer by bubbles, relative to natural convection, increases with both zinc concentration and hydrogen current density. Under industrial conditions of high zinc concentration (0.9 mmol/cm 3 ZnO) and high current densities (-0.24 A/cm2), the effect of the hydrogen bubbles is predominant even if the hydrogen current efficiency is low (3.3%), the Sherwood numbers being, respectively, 424 and 115. The data obtained in this work and others give support to the dimensionless correlation StSc 0.~ = 0.035(FrRe) -0.2~

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Section: Discussionmentioning

confidence: 87%

Ionic Mass Transfer of Zinc in Alkaline Solutions with Simultaneous Hydrogen Evolution

St‐Pierre

Piron

1992

J. Electrochem. Soc.

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“…Attached bubbles are known to cause unfavorable mass transport and ohmic and kinetic effects due to the blockage of catalytic sites. , Before elaborating on these effects, we begin with a brief discussion of the bubble coverage of electrodes (Θ), , which is defined as the fraction of an electrode surface covered by attached bubbles. Numerous experimental investigations have been conducted to obtain information on how bubble coverage varies with current density. ,− A typical experiment for measuring bubble coverage involves the use of a camera to record the bubble population and the diameters of adhering bubbles. Figure shows a collection of data obtained in stagnant electrolyte (electrolyte without flow and with unhindered bubble release), summarized by Vogt .…”

Section: What Are the Impacts Of Gas Bubbles On A Gas Evolution React...mentioning

confidence: 99%

Gas Bubbles in Electrochemical Gas Evolution Reactions

2019

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Electrochemical gas evolution reactions are of vital importance in numerous electrochemical processes including water splitting, chloralkaline process, and fuel cells. During gas evolution reactions, gas bubbles are vigorously and constantly forming and influencing these processes. In the past few decades, extensive studies have been performed to understand the evolution of gas bubbles, elucidate the mechanisms of how gas bubbles impact gas evolution reactions, and exploit new bubble-based strategies to improve the efficiency of gas evolution reactions. In this feature article, we summarize the classical theories as well as recent advancements in this field and provide an outlook on future research topics.

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“…Evolution of hydrogen, chlorine, and oxygen from stagnant aqueous electrolyte liquids ͑aqueous solutions of KOH, HCl, H 2 SO 4 ) at various electrode materials ͑Ni, Pt, Cu, C, Pb, Hg͒ according to various workers2,5,[11][12][13][14][15][16][17][18][19] and data from present work. Temperature 20-30°C, ambient pressure.…”

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confidence: 98%

Effect of Electrolyte Flow on the Bubble Coverage of Vertical Gas-Evolving Electrodes

Balzer¹,

Vogt²

2003

J. Electrochem. Soc.

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The bubble coverage of vertical gas-evolving electrodes with forced upward electrolyte flow is studied systematically in laboratory experiments. A substantial decrease with increasing flow velocity past the electrode is found for various electrode materials of anodes and cathodes. A theoretical analysis explains the action of mechanical forces on the break-off diameter of bubbles exposed to flowing electrolytes. A simplified design equation for practical estimates is proposed.Reliable knowledge of the electrode area covered by adhering bubbles is of utmost importance for assessing the operational behavior of gas-evolving electrodes. The value is not only relevant to the ohmic voltage drop of the so-called bubble curtain before the electrode, but also for the extent of mass and heat transfer. The bubble coverage controls the actual current density and thus both the overpotential and the limiting current density. 1 A variation of the bubble coverage with distance from the leading edge contributes to the current distribution over the electrode.It is not astonishing that numerous experimental investigations were conducted to get information on the value of the bubble coverage, particularly its dependence on the current density. Nearly all of these investigations refer to stagnant electrolyte, i.e., liquids without forced flow, mostly in experimental devices where substantial flow past the electrode cannot develop. However, industrial cells are commonly operated with forced upward flow or designed in such a way that substantial free flow induced by gas bubbles develops. Owing to experimental difficulties, data under these conditions are rare. A few data were published by Sillen obtained at a cell with vertical electrodes. 2,3 More detailed data were obtained at horizontal electrodes facing upward. 4 However, industrial gas-evolving electrodes are in a vertical position, wherever possible, to enhance gas release from the interelectrode space. It is the object of the present paper to study the conditions at vertical electrodes of various electrode materials operated as anodes and cathodes with forced flow of varying rates. Bubble Coverage in Stagnant LiquidsTo distinguish the active electrode surface area from the geometrical one, the ͑fractional͒ bubble coverage was introduced by Ibl and Venczel 5 in 1961. It was defined as the fraction of the electrode area covered on the average by bubbles sitting on it. A stricter definition was given in 1980 defining the covered area as that obtained by perpendicular projection of the bubble contours to the electrode, referred to the electrode mean area pertinent to each adhering bubble. 6 This definition is superior in that it considers that the current density on the shadowed area below adhering bubbles with contact angles smaller than 90°͑which is a common case in aqueous electrolytes͒ is small, 7-9 and may approximately be neglected for the present purpose.The value of the bubble coverage is controlled by the bubble population density on the electrode surface, i.e., the number ...

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A population balance approach to the study of bubble behaviour at gas-evolving electrodes

Cited by 11 publications

References 12 publications

Ionic Mass Transfer of Zinc in Alkaline Solutions with Simultaneous Hydrogen Evolution

Ionic Mass Transfer of Zinc in Alkaline Solutions with Simultaneous Hydrogen Evolution

Gas Bubbles in Electrochemical Gas Evolution Reactions

Effect of Electrolyte Flow on the Bubble Coverage of Vertical Gas-Evolving Electrodes

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