The Behaviors of Interfacial Nanobubbles on Flat or Rough Electrode Surfaces in Electrochemistry

The existence of interfacial nanobubbles on electrode surfaces is thought to block the active area, leading to a considerable decrease in the energy conversion efficiency. Gaining insight into how bubbles form on electrodes will be beneficial for designing effective electrochemical cells and enhancing the electrolytic efficiency. In this article, molecular dynamics (MD) simulations are employed to make a systematic comparison of behaviors of interfacial nanobubbles on both flat and rough electrode surfaces in electrochemistry. On a flat electrode surface, bubble nucleation can be categorized into single-site and multisite nucleation, influenced by the electrode sizes and electrolytic rates. The various rates of gas production result in three different scenarios for single-site nucleation: "growth-growth," "growth-shrinking," and "growth-stabilization" behaviors. On a rough one, bubbles are pinned at an early stage. Either through cooperative release or self-release, the bubbles continue to grow until the influx and outflux gas of the bubble reach an equilibrium. In addition, the evolutionary mechanism of interface nanobubbles was discussed on a rough nanoelectrode surface. Based on the dynamic equilibrium mechanism, a theoretical relationship between contact angle and base diameter of equilibrium interfacial nanobubbles was developed. The theoretical model can qualitatively describe the simulation observation of how bubble's shape depends on the electrode surface morphology.