Study of the Marangoni effect during electrolytic gas evolution

lectrolytic gas evolution is a fundamental phenomenon occurring in a large number of industrial applications. Near the electrode, bubble growth is understood to appear due to mass flux of dissolved gas across the bubble interface from a supersaturated electrolyte. Because of related thermal, electrical or solutal effects, a gradient of the surface tension along the interface may exist. The resulting shear stress would cause convection at the interface (Marangoni effect), which may affect the mass transfer across the interface during growth and also the departure of the gas bubble. This Marangoni effect was unveilled only recently in an experimental study [1]. The present work aims to investigate the origin of the effect in more detail. Numerical simulations are performed including only the thermal Marangoni effect near a hydrogen gas bubble growing electrochemically at a microelectrode in an acidic electrolyte. The simulation results are compared with experimental data of the near-bubble convection obtained by Particle Tracking Velocimetry (PTV) and by temperature measurements. The comparison allows to conclude on a strong thermocapillary effect at the microelectrode [2]. The related force on the bubble is found to retard the release of the bubble.

[1] X. Yang et al, Phys. Chem. Chem. Phys., 20: 11542-11548. 2018.
[2] J. Massing et al., Electrochim. Acta. 2019. IN PRESS