Minimum current for detachment of electrolytic bubbles

TL;DR

This study uses molecular dynamics simulations and an extended stability theory to analyze nanobubble behavior during water electrolysis, identifying the minimum current needed for bubble detachment and detailing growth dynamics.

Contribution

It introduces a generalized stability theory incorporating electrolytic gas influx and real gas law, enabling analytical prediction of nanobubble detachment conditions.

Findings

Nanobubbles grow to equilibrium or detach depending on current.

The radius growth follows R∝t^{1/2} and R∝t^{1/3} before detachment.

The minimum current for bubble detachment is analytically derived.

Abstract

The efficiency of water electrolysis is significantly impacted by the generation of micro- and nanobubbles on the electrodes. Here molecular dynamics simulations are used to investigate the dynamics of single electrolytic nanobubbles on nanoelectrodes. The simulations reveal that, depending on the value of current, nucleated nanobubbles either grow to an equilibrium state or grow unlimitedly and then detach. To account for these findings, the stability theory for surface nanobubbles is generalized by incorporating the electrolytic gas influx at the nanobubble's contact line and adopting a real gas law, leading to accurate predictions for the numerically observed transient growth and stationary states of the nanobubbles. With this theory, the minimum current for bubble detachment can also be analytically derived. In the detachment regime, the radius of the nanobubble first increases as $R\propto t^{1/2}$ and then as $R\propto t^{1/3}$, up to bubble detachment.