Three-dimensional coupling numerical simulation of two-phase flow and electrochemical phenomena in alkaline water electrolysis

Abstract

Alkaline water electrolysis has the advantage of scalability for industrial-scale mass production of hydrogen; however, it is operated under a lower current density than other methods of water electrolysis because a high overpotential resulting from ion transport limitations will occur at high current density. Bubble dynamics can both prevent ion transport by its existence and accelerate it by bubble-induced flow. In this study, we conduct three-dimensional coupling numerical simulations of two-phase flow and electrochemical phenomena to elucidate the mechanisms by which microscale bubble dynamics influence ion transport and the cell overpotential. We find that the flow induced by rising microbubbles enhances ion transport to the anode and suppresses the cell overpotential. Moreover, bubble atomization further suppresses the overpotential because smaller bubbles approach the anode more closely than larger ones and accelerate ion transport to the anode surface.