Imaging nanobubble nucleation and hydrogen spillover during electrocatalytic water splitting

Significance

Due to the highly dynamic nature and intrinsic heterogeneity of the electrochemical interface, it is critical to develop new tools so that electrochemical activities can be imaged with high sensitivity and high spatial and temporal resolution. We demonstrate the unique ability to image nucleation and growth of individual hydrogen nanobubbles during electrocatalytic water splitting using superresolution fluorescence microscopy. This method allows us to compare electrocatalytic activity of different electrode materials toward hydrogen evolution reaction and observe in real time the effect of hydrogen spillover from electrode-supported gold nanocatalysts.

Abstract

Nucleation and growth of hydrogen nanobubbles are key initial steps in electrochemical water splitting. These processes remain largely unexplored due to a lack of proper tools to probe the nanobubble’s interfacial structure with sufficient spatial and temporal resolution. We report the use of superresolution microscopy to image transient formation and growth of single hydrogen nanobubbles at the electrode/solution interface during electrocatalytic water splitting. We found hydrogen nanobubbles can be generated even at very early stages in water electrolysis, i.e., ∼500 mV before reaching its thermodynamic reduction potential. The ability to image single nanobubbles on an electrode enabled us to observe in real time the process of hydrogen spillover from ultrathin gold nanocatalysts supported on indium–tin oxide.