On the electrolyte convection around a hydrogen bubble evolving at a microelectrode under the influence of a magnetic field

The flow around an evolving hydrogen bubble on a microelectrode (0.1 mm in diameter) under the influence of an electrode-normal magnetic field was investigated to clarify the effect of the imposed flow on the detachment of the bubble from the electrode. Therefore, water electrolysis was carried out in a 1 M H2SO4 solution under potentiostatic conditions for different potentials in the presence of a magnetic field normal to the horizontal electrode surface. Measurements of the current oscillations and microscopic high-speed imaging were used to analyze the periodic bubble growth. The three-dimensional flow in the bulk of the cell and around the evolving bubble was measured in parallel by applying different particle imaging and tracking techniques. In addition, a numerical study of the flow was conducted to support the experimental results. The results demonstrate that the hydrodynamic force imposed by the Lorentz-force-driven-convection has a very small stabilizing effect on the bubble. However, a strong flow in the vicinity of the bubble was observed that may reduce the local supersaturation of dissolved hydrogen. Furthermore, large flow velocities close to the bubble surface indicate a strong motion of the mobile liquid-gas interface that might be significant for the bubble evolution process.