Relationship between bubble generation behavior and hydrogen evolution reaction performance at high current densities during alkaline water electrolysis

Alkaline water electrolysis (AWE) has attracted considerable attention in recent years as a means to produce hydrogen. However, one problem associated with AWE is the increase in overpotential at high current densities, which is attributed to bubble coverage on the electrode surface. It is therefore important to understand the bubble generation behavior to ultimately reduce the overpotential. In this study, a method was established to measure the resistance components from the electrolytic reaction and bubble coating separately based on the use of electrochemical impedance spectroscopy. The results were related to the bubble generation behavior on a Ni electrode, as observed using a high-speed camera. Consequently, a model for the degradation of the electrolytic efficiency due to bubble generation was devised, and the effect of the bubble coverage layer was quantitatively evaluated.