Scanning Electrochemical Cell Microscope Study of Individual H2 Gas Bubble Nucleation on Platinum: Effect of Surfactants

Abstract Adsorption of gas bubbles on the electrode surface is one of important issues responsible for the reduced efficiency of water electrolysis. Understanding the bubble phenomena can benefit the management of gas bubbles. In this study, we carried out a single-entity electrochemical study of individual gas bubbles on the Pt electrode using scanning electrochemical cell microscopy. Different from conventional ensemble methods, the bubble nucleation behaviour and the effect of surfactants (perfluorooctanoic acid (PFOA), hexadecyl trimethyl ammonium bromide (CTAB) and siloxane defoamer) on the electrode surface were investigated at microscale resolution. Statistical analysis of individual nucleation event showed the stochastic characteristic and the addition of surfactant could significantly improve the stability of gas bubbles especially those formed in small nanopipets. A correlation between the critical supersaturation (or Faradic current) for bubble nucleation and surface tension with was observed, which was consistent with classic nucleation theory. However, chronoamperometry study showed that the water electrolysis efficiency after surfactant addition was not significantly improved. This study provided unique insights into understanding of nucleation event at single-entity.