Numerical simulations of bubble oscillations and detachment on electrodes in aqueous electrolysers used for green hydrogen production*

Bubble formation, detachment and dynamics are of key importance for designing efficient electrochemical processes such as hydrogen production. In aqueous electrolytic solutions, the dissolved gas supersaturation, the continuous phase dynamics, as well as the surface properties influence bubble formation and the resulting void fraction. In addition, the bubble sizes and their frequency of detachment affect the electrode coverage and resulting overpotentials, which can be detrimental to efficient electrochemical processes. While research has focused on hydrophobic micro-structured surfaces to minimize the adhesion forces and therefore bubble diameters, less attention has been brought to dynamic boundary conditions at the surface of the electrode due to the change in contact angle as a result of temperature, potential and concentration gradients along the electrode. In this study, we use the open-source platform OpenFOAM to solve the one-fluid formulation of the Navier-Stokes equations as well as the transport of dissolved gases in the aqueous solution. The fluid transport equations are coupled to the electrostatic equations and the contact angle at the electrode varies with the voltage. The methodology is validated through comparison with literature data and simulations are performed to study the effects of operating conditions, namely varying contact angle and shear flow on bubble detachment.