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 counteract-bubbles-with-bubbles strategy for macroscopic bubble engineering. This strategy is expected to promote the structural design of practical gas-evolution devices with minimized mass transfer resistance.