Improving the efficiency of industrial water electrolysis for hydrogen production is a critical aspect of energy transition. During water electrolysis, hydrogen is produced at the cathode, resulting in the formation of bubbles. The reaction creates a gradient of the electrolyte concentration that causes local surface tension variations along the bubble surfaces. This leads to a shear stress that causes convection, which is called the solutal Marangoni effect [1]. Marangoni convection can affect the gas evolution process during water electrolysis by improving the mass transfer [2].
In this study, we simulate solutal Marangoni flow occurring near a single hydrogen bubble attached to an electrode in an alkaline electrolyte in a narrow channel with a relatively high current density. Furthermore, we investigate the effect of Marangoni flow on the velocity field, bubble growth rate, species concentration, potential, and (local) current density. To solve the governing equations including the Navier-Stokes equations, the mass transfer equations, and the potential equation for the tertiary current density, we use a sharp interface immersed boundary method. An elegant method for applying the Marangoni stress boundary condition at the bubble interface using the immersed boundary method is proposed and implemented. We find a significant Marangoni flow. Figure 1 compares the velocity fields for the case with(out) Marangoni flow at the x-y plane in the center of the computational domain when the bubble grows to a radius of 25 μm. In the case of no Marangoni flow, the maximum fluid velocity value is 2.4 mm/s, while in Marangoni flow, it is 20.2 mm/s.

[1] S. Park, L. Liu, C. Demirkır , O. van der Heijden , D. Lohse, D. Krug, M. T. Koper, Solutal Marangoni effect determines bubble dynamics during electrocatalytic hydrogen evolution, Nature chemistry, 15(11), pp. 1532-1540, 2023.

[2] X. Yang, D. Baczyzmalski, C. Cierpka , G. Mutschke , K. Eckert, Marangoni convection at electrogenerated hydrogen bubbles, Physical Chemistry Chemical Physics, 20(17), pp. 11542-11548, 2018.