Microscopic high-speed video observation of oxygen bubble generation behavior and effects of anode electrode shape on OER performance in alkaline water electrolysis

Abstract

An important difficulty associated with alkaline water electrolysis is the rise in anode overpotential attributable to bubble coverage of the electrode surface. For this study, a system with a high-speed video camera was developed, achieving in-situ observation of bubble generation on an electrode surface, monitoring an area of 1.02 mm 2 at 6000 frames per second. The relation between polarization curve (current density up to 3.0 A cm −2 ) and oxygen bubble generation behavior on nickel electrodes having cylindrical wires and rectangular wires of different sizes (100–300 μm) was clarified. The generated bubbles slide upward, contacting the electrode surface and detaching at the top edge. Observations indicate that small electrodes have short bubble residence time and thin bubble covering layer on the electrode. As a result, the small electrode diameter contributes to smaller overpotential at high current density. • Microscopic high-speed video observation system for bubble generation was developed. • Bubble motion was observed in a 1.02 mm 2 area at 6000 frames per second. • Small cylindrical electrodes showed high performance for oxygen evolution reaction. • Generated bubbles move up the electrode surface and detach at the electrode top. • Small electrodes provide short electrode residence time and small detached bubbles.