Investigation of Hydrogen Bubble Growth in Alkaline Water Electrolysis Using an Immersed Boundary Method

Enhancing the efficiency of industrial water electrolysis for hydrogen production is crucial for the energy transition. The (hydrogen) bubbles play a fundamental role on determining the electrolysis efficiency. Hydrogen is produced at the cathode, which form bubbles due to the diffusion of dissolved hydrogen in the surrounding supersaturated electrolyte. The growth of the bubbles is determined by diffusive and convective mass transfer. In turn, the presence as well as the growth of the hydrogen bubbles significantly affect the electrolysis process at the cathode.
In the present study, a single growing bubble attached to a vertical cathode in a 30 wt% KOH solution is simulated using a numerical model on solving the Navier-Stokes and mass transport equations. A sharp interface immersed boundary with an artificial compressibility method for the pressure is employed. The current density is assumed to be constant. Careful verifications have been done for the grid independency, mass and momentum conversation of this numerical model. The simulations so far successfully predict the gradual growth of the hydrogen bubble, and the results indicate a regime of approximately linear growth rate.