Desorption of hydrogen from an electrode surface under influence of an external magnetic field – In-situ microscopic observations

Koza, Jakub Adam; Mühlenhoff, Sascha; Uhlemann, Margitta; Eckert, Kerstin; Gebert, A.; Schultz, L.

doi:10.1016/j.elecom.2008.12.010

Cited by 61 publications

(33 citation statements)

References 9 publications

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“…The influence of an external magnetic field on the electrochemical deposition of metals such as Co, Fe, Ni, and its alloys on a flat electrode was mainly investigated [14][15][16][17][18][19][20][21][22][23][24]. So far, limited studies have been done to examine the influence of the magnetic field applied during cobalt deposition into Al 2 O 3 pores on the magnetic properties of the cobalt nanowires, and previous studies had not provided clear results [25][26][27].…”

Section: Introductionmentioning

confidence: 99%

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Structure and magnetic properties of Co nanowires electrodeposited into the pores of anodic alumina membranes

Dobosz

Gumowska

Czapkiewicz

2014

J Solid State Electrochem

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Cobalt nanowires were obtained in the process of electrodeposition into pores of an alumina membrane. Structural research (XRD, TEM) of Co revealed the facecentered cubic structure. However, the existence of the hexagonal structure cannot be excluded due to strong texture. The influences of an external magnetic field and Al 2 O 3 membrane geometry on magnetic properties of obtained wires were examined. It was found that cobalt nanowires exhibit pronounced shape anisotropy in a direction parallel to the wire axis. The highest influence on the magnetic properties is ascribed to the nanowires geometry i.e., height, diameter, and distances between single wires. Application of an external magnetic field in a perpendicular direction to the sample surface during cobalt electrodeposition increases magnetic anisotropy with a privileged direction along the wire axis. Application of the magnetic field in a parallel direction to the sample surface changes the direction of magnetization.

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Section: Introductionmentioning

confidence: 99%

“…The changes are ascribed to magnetohydrodynamic (MHD) convection induced by the Lorentz force [14]. The increase of convection inside the diffusion layer affects the rate of the ions transport which in turn alters pH values near the electrode surface.…”

Section: Introductionmentioning

confidence: 99%

Structure and magnetic properties of Co nanowires electrodeposited into the pores of anodic alumina membranes

Dobosz

Gumowska

Czapkiewicz

2014

J Solid State Electrochem

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“…14,15 Moreover, a reduced void fraction in the electrode gap and a lower bubble coverage on large electrodes was observed for increasing magnetic field strengths and thus increasing magnitudes of the Lorentz force in the case of an electrode-parallel magnetic field. 16, 17 Koza et al [18][19][20] showed that both the bubble size and the fractional bubble coverage on large planar electrodes were decreased by the application of magnetic fields, irrespective of the magnetic field orientation. 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.…”

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confidence: 99%

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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“…6b, c, e and f), irrespective of its configuration, suggesting that magnetic field supports desorption of hydrogen from the electrode surface. Indeed desorption of hydrogen from the electrode surface has been shown to be improved by a magnetic field regardless of its relative-to-electrode configuration [26,29,30]. This effect has been divided into macroscopic and microscopic MHD flow induced by a Lorentz force, i.e.…”

Section: Morphologymentioning

confidence: 98%

Electrocrystallisation of CoFe alloys under the influence of external homogeneous magnetic fields—Properties of deposited thin films

Koza¹,

Karnbach²,

Uhlemann³

et al. 2010

Electrochimica Acta

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Desorption of hydrogen from an electrode surface under influence of an external magnetic field – In-situ microscopic observations

Cited by 61 publications

References 9 publications

Structure and magnetic properties of Co nanowires electrodeposited into the pores of anodic alumina membranes

Structure and magnetic properties of Co nanowires electrodeposited into the pores of anodic alumina membranes

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

Electrocrystallisation of CoFe alloys under the influence of external homogeneous magnetic fields—Properties of deposited thin films

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