Imaging Microbubble Nucleation and Growth on Pt Ultramicroelectrodes

Herein, we report the dynamic nucleation and growth behavior of individual hydrogen microbubbles on a thin-film Pt ultramicroelectrode (UME). By depositing and patterning a thin layer of platinum metal on a transparent, conductive, but electrocatalytically inert indium-tin oxide (ITO) substrate, we are able to obtain individual Pt UMEs and use them to image hydrogen microbubbles formed by the hydrogen evolution reaction (HER) in an acid solution. The use of reflection microscopy and the semitransparent Pt UME allows us to observe hydrogen microbubbles as they nucleate on the UME surface, track their growth with time, and image their movement and bubble-bubble interaction on the electrode. Our results show that H₂ microbubbles formed on a Pt UME tend to move toward the center of the microelectrode as they grow bigger in size and extend their contact area on the electrode. Our results suggest multiple microbubbles forming on the same electrode compete with each other for bubble growth, following a mechanism similar to Ostwald ripening.