Bubble Dynamics: From Single-Bubble Growth to Dual-Bubble Coalescence

Bubble engineering enhances mass transfer in electrochemical gas-evolution devices by accelerating bubble detachment. Understanding dynamics from single-bubble growth to microscale bubble-bubble interactions is fundamental to bubble engineering but remains challenging. Herein, by integrating ultramicroelectrode electrochemistry with high-speed dark-field microscopy, we correlate electrochemical responses to bubble dynamics with synchronized optical signals, revealing dynamics beyond the single-bubble regime at millisecond temporal resolution and microscale spatial resolution. At the single-bubble level, position-dependent growth dynamics (edge vs center) of O₂ bubbles generated during water electrolysis are characterized. An electrochemical method quantifies contact angles using residual current ratios and bubble diameters, revealing superior aerophobicity (θ ≈ 170°) of electrogenerated Ni(OH)₂ surfaces. Crucially, beyond the single-bubble regime, we decipher electrode-bubble interactions and bubble-bubble interactions by prepositioning an O₂ bubble adjacent to the electrode. Electrode-bubble interactions reveal electrochemically driven growth of a neighboring bubble and ∼30% enhancement of local mass transfer. Bubble-bubble interactions demonstrate coalescence-induced recovery of bubble-blocked current within ∼4 ms via accelerated detachment. These results highlight interactions transcending the single-bubble regime, specifically pairwise bubble interactions, and establish a mechanistic framework of <i>counteract-bubbles-with-bubbles</i> strategy for macroscopic bubble engineering. This strategy is expected to promote the structural design of practical gas-evolution devices with minimized mass transfer resistance.