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

Area of Science:

• Electrochemistry
• Fluid Dynamics
• Materials Science

Background:

• Bubble engineering is crucial for enhancing mass transfer in electrochemical gas-evolution devices.
• Understanding bubble dynamics, from single-bubble growth to microscale interactions, is key but challenging.
• Current methods lack the resolution to capture these complex dynamics.

Purpose of the Study:

• To correlate electrochemical responses with bubble dynamics at high temporal and spatial resolutions.
• To investigate single-bubble growth, electrode-bubble interactions, and bubble-bubble interactions.
• To establish a mechanistic framework for bubble engineering strategies.

Main Methods:

• Integration of ultramicroelectrode electrochemistry with high-speed dark-field microscopy.
• Synchronized optical and electrochemical signal acquisition.
• Characterization of oxygen (O₂) bubble dynamics during water electrolysis.

Main Results:

• Characterized position-dependent growth dynamics of O₂ bubbles.
• Quantified superior aerophobicity (contact angle ≈ 170°) of electrogenerated Ni(OH)₂ surfaces.
• Demonstrated electrode-bubble interactions enhancing local mass transfer by ~30% and bubble-bubble interactions enabling rapid current recovery (~4 ms) via coalescence-induced detachment.

Conclusions:

• Interactions beyond the single-bubble regime, particularly pairwise bubble interactions, are critical.
• Established a mechanistic framework for a 'counteract-bubbles-with-bubbles' strategy.
• This strategy is expected to minimize mass transfer resistance in practical gas-evolution devices.