Modulation of Nanobubble Behaviors through Ionic Liquids during CO2 Electroreduction

CO2 electroreduction is a gas-consuming and -generating process, which is prevalently accompanied by the formation of bubbles. Bubbles adhered on the electrode surface severely affect the electrocatalytic efficiency. However, the formation and regulation of nanobubbles have not been studied in depth. In this work, the evolution behaviors of individual CO nanobubbles are investigated at gold nanoelectrodes, where CO is generated through CO2 electroreduction in ionic liquids (ILs). The recorded voltammograms demonstrate that the formation and stability of CO nanobubbles are enhanced because of improving the surface activity by adding ILs. Additionally, combining experimental results with classic nucleation theory, the regulation rules of different ILs on CO nanobubble nucleation are revealed: (i) with longer carbon chains, nanobubble formation can be facilitated by altering the surface energy and hydrophobic properties of the electrode through ILs; (ii) the increase of fluorine atoms in the anion of ILs decreases the driving force of nanobubble nucleation, while the introduction of amino groups into cations decreases the critical concentration of nanobubble nucleation. These results contribute to understanding CO nanobubbles and regulating them in further studies of CO2 electroreduction with ionic liquids.