Near-wall measurements of the bubble- and Lorentz-force-driven convection at gas-evolving electrodes

Baczyzmalski, Dominik; Weier, Tom; Kähler, Christian J.; Cierpka, Christian

doi:10.1007/s00348-015-2029-0

Cited by 33 publications

(10 citation statements)

References 45 publications

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“…The MHD convecz E-mail: Dominik.Baczyzmalski@unibw.de tion in an electrode-parallel field is characterized by a strong shear flow with high flow velocities close to the electrode surface as shown by measurements of the velocity field in the electrode gap of an alkaline electrolyzer. 21,22 Thus, the enhanced bubble detachment for parallel fields was generally attributed to the effect of the strong MHD convection along the electrode, similar to the findings of other studies investigating the bubble detachment dynamics under forced convection. 23,24 However, the situation for a magnetic field perpendicular to the electrode is unclear.…”

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confidence: 85%

On the Electrolyte Convection around a Hydrogen Bubble Evolving at a Microelectrode under the Influence of a Magnetic Field

Baczyzmalski

Karnbach

Yang

et al. 2016

J. Electrochem. Soc.

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Water electrolysis was carried out in a 1 M H 2 SO 4 solution under different potentiostatic conditions in the presence of a magnetic field oriented normal to the horizontal microelectrode (100 μm in diameter). The imposed magnetohydrodynamic (MHD) electrolyte flow around the evolving hydrogen bubble was studied to clarify the effect on the detachment of the bubble from the electrode and the mass transfer toward the electrode. Different particle imaging and tracking techniques were applied to measure the three-dimensional flow in the bulk of the cell as well as in close vicinity of the evolving bubble. The periodic bubble growth cycle was analyzed by measurements of the current oscillations and microscopic high-speed imaging. In addition, a numerical study of the flow was conducted to support the experimental results. The results demonstrate that the MHD flow imposes only a small stabilizing force on the bubble. However, the observed secondary flow enhances the mass transfer toward the electrode and may reduce the local supersaturation of dissolved hydrogen. Renewable energy technologies have become increasingly important in view of the worldwide rising CO 2 emissions. The growing application of volatile energy sources such as wind and solar power requires efficient energy storage and distribution systems in order to sustain stability in the electrical grid. Hydrogen shows great potential for long-term energy storage as well as mobile units employing fuel cells as it provides a large energy density. Moreover, high purity hydrogen (and oxygen) can be directly generated from the electricity produced by a wind turbine or solar panel by the electrolysis of water. However, one main challenge for the establishment of water electrolysis on an industrial scale is its relatively low efficiency, typically in the order of 60% for conventional alkaline water electrolyzers. 1 A considerable part of the losses is the result of hydrogen and oxygen gas bubbles evolving at, and sticking to the electrodes' surfaces, thus hindering the formation of new gas bubbles. Furthermore, they reduce the effective electrical conductivity of the electrolyte, which leads to an increased ohmic voltage drop. The accelerated removal of gas bubbles from the electrode's surface and the bulk was studied by many researchers to improve the efficiency of the process.2-6 Forced convection has been found to be able to enhance the detachment of bubbles from the electrode and therefore reduce the fractional bubble coverage significantly.7-12 A relatively simple method that has recently attracted considerable research interests in this context is the application of magnetic fields. The superposition of a magnetic field on the inherent electric field gives rise to Lorentz forces f L = j × B acting as body forces directly on the electrolyte, where j denotes the current density and B is the magnetic induction, respectively. 13 The flow generated by these Lorentz forces is often referred to as the magnetohydrodynamic (MHD) effect.It was shown that stirring with...

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supporting

confidence: 85%

On the Electrolyte Convection around a Hydrogen Bubble Evolving at a Microelectrode under the Influence of a Magnetic Field

Baczyzmalski

Karnbach

Yang

et al. 2016

J. Electrochem. Soc.

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“…The second is entrainment of the microbubbles in the wake of the millimeter bubble. Because for the Type A surface the mean diameter of largesized bubbles is more than 4 mm, almost all of them show a wobbling motion (e.g., Baczyzmalski et al [33]). When a millimeter-sized bubble with wobbling motion rises near the wall, its wake causes significant diffusion of microbubbles near the wall (Fig.…”

Section: Behavior Of Bubble Layermentioning

confidence: 99%

Effect of wall surface wettability on collective behavior of hydrogen microbubbles rising along a wall

Kitagawa

Denissenko

Murai

2017

Experimental Thermal and Fluid Science

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“…In particular, references [49][50] contain treatment of various magnetoelectrolysis problems by way of simulations and experiments, examining different orientations of the Lorentz force with respect to the buoyancy force. Baczymalski and co-authors dealt with Lorentz-force effects in bubbledriven convection at gas-evolving electrodes [51][52]. In an experimental study, they showed that applying a magnetic field to a cell for water electrolysis can improve its efficiency by enhancing bubble detachment [51].…”

Section: Accepted Manuscriptmentioning

confidence: 99%

“…Baczymalski and co-authors dealt with Lorentz-force effects in bubbledriven convection at gas-evolving electrodes [51][52]. In an experimental study, they showed that applying a magnetic field to a cell for water electrolysis can improve its efficiency by enhancing bubble detachment [51]. In another paper [52], they examined the effect of buoyancy and Lorentz forces on the evolution of a single H2 bubble via both simulations and experiments.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Natural convection effects in electrochemical systems

Novev

Compton

2018

Current Opinion in Electrochemistry

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights Recent work on natural convection in electrochemistry is reviewed.  Experimental and theoretical/simulation studies in the area are considered.  Free convection driven by concentration and/or temperature gradients is discussed.  Natural convection in systems such as electrorefining and fuel cells is covered.  A critical assessment of the concept of 'spontaneous convection' is given.

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Near-wall measurements of the bubble- and Lorentz-force-driven convection at gas-evolving electrodes

Cited by 33 publications

References 45 publications

On the Electrolyte Convection around a Hydrogen Bubble Evolving at a Microelectrode under the Influence of a Magnetic Field

On the Electrolyte Convection around a Hydrogen Bubble Evolving at a Microelectrode under the Influence of a Magnetic Field

Effect of wall surface wettability on collective behavior of hydrogen microbubbles rising along a wall

Natural convection effects in electrochemical systems

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