Comparative study of bubble forming sites at the laser-induced microstructure on a Ni electrode during hydrogen and oxygen evolution reactions

Abstract

We study the formation of hydrogen and oxygen bubbles on the identical Ni electrode with a single laser-induced microstructure to understand the role of local surface morphology on bubble formation. All the forming sites of hydrogen bubbles are found at the microstructure, while those of oxygen bubbles are found not only at the microstructure but also on the flat area. Interestingly, not all but only a few of the sites at the microstructure produce both hydrogen and oxygen bubbles, and we find that these sites have partially confined structures. In contrast, the presence of oxygen bubble forming sites on the flat area implies that the local surface morphology is not the only decisive factor to be a bubble forming site. Through the elemental analysis of the electrode surface, we find the tendency that the sites with more nickel oxides show the less bubble forming activities.