Investigation of the hydrogen bubble effect on the overpotential in an alkaline water electrolyzer

Abstract

The efficiency of alkaline water electrolysis (AWE) technology is highly influenced by the electrogenerated bubbles. Most of the efficiency improvement methods based on the enhancement of the flow field have been evaluated on the overall bubble effect. In this work, we distinguish the different bubble effects and investigate their effects on the overpotential, respectively. An experimental investigation was carried out in a vertical plane electrode electrolyzer with forced convection. The correction factor for the outlet gas flow rate on the surface of the cathodic electrode was obtained by comparing experimental and theoretical results, whose value was around 1.6 under the conditions of this study. Meanwhile, according to the experimental results, the two-way coupling Euler-Lagrange multiphase computational fluid dynamics (CFD) model was modified. Experimental and numerical results indicate that the electrolyte inlet velocity at a higher current density has a stronger influence on the hydrogen bubble curtain than that at a lower current density. More importantly, the bubbles covering on the electrode have a stronger influence on the overpotential than that dispersing in the electrolyte, and it is about 100 times difference.