In the past Christian Cierpka has collaborated on articles with Julian Massing and Tom Weier. One of their most recent publications is Thermocapillary convection during hydrogen evolution at microelectrodes☆. Which was published in journal Electrochimica Acta.

More information about Christian Cierpka research including statistics on their citations can be found on their Copernicus Academic profile page.

Christian Cierpka's Articles: (3)

Thermocapillary convection during hydrogen evolution at microelectrodes☆

AbstractThe origin of strong electrolyte flow during water electrolysis is investigated, that arises at the interface between electrolyte and hydrogen bubbles evolving at microelectrodes. This Marangoni convection was unveiled only recently (Yang et al., PCCP, 2018, [1]) and is supposed to be driven by shear stress at the gas-liquid interface caused by thermal and concentration gradients. The present work firstly allows a quantification of the thermocapillary effect and discusses further contributions to the Marangoni convection which may arise also from the electrocapillary effect. Hydrogen gas bubbles were electrolytically generated at a horizontal Pt microelectrode in a 1 M H2SO4 solution. Simultaneous measurements of the velocity and the temperature field of the electrolyte close to the bubble interface were performed by means of particle tracking velocimetry and luminescent lifetime imaging. Additionally, corresponding numerical simulations of the temperature distribution in the cell and the electrolyte flow resulting from thermocapillary stress only were performed. The results confirm significant Ohmic heating near the micro-electrode and a strong flow driven along the interface away from the microelectrode. The results further show an excellent match between simulation and experiment for both the velocity and the temperature field within the wedge-like electrolyte volume at the bubble foot close to the electrode, thus indicating the thermocapillary effect as the major driving mechanism of the convection. Further away from the microelectrode, but still below the bubble equator, however, quantitative differences between experiment and simulation appear in the velocity field, whereas the temperature gradient still matches well. Thus, additional effects must act on the interface, which are not yet included in the present simulation. The detailed discussion tends to rule out solution-based effects, generally referred to as solutal effects, whereas electrocapillary effects are likely to play a role. Finally, the thermocapillary effect is found to exert a force on the bubble which is retarding its departure from the electrode.

On the challenges for reliable measurements of convection in large aspect ratio Rayleigh-Bénard cells in air and sulfur-hexafluoride

Highlights•Optically accessible facility for high Ra numbers using pressurized air and SF6 is presented.•Measurement error sources for stereoscopic PIV are discussed.•First time velocity measurements at fully turbulent Rayleigh-Bénard convection in air and SF6.•Turbulent superstructures can be clearly identified.

Confinement of paramagnetic ions under magnetic field influence: Lorentz versus concentration gradient force based explanations

AbstractConcentration variations observed at circular electrodes with their axis parallel to a magnetic and normal to the gravitational field have previously been attributed elsewhere to the concentration gradient force only. The present paper aims to show that Lorentz force driven convection is a more likely explanation.

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