Combined Effects of Bubble Size Ratio on Coalescence-Driven Dynamics and Electrode Dimensions on Electrolytic Performance

Abstract

Gas bubble formation and detachment during water electrolysis critically affect electrochemical performance, particularly at high current densities. Bubble dynamics at the electrode interface are strongly influenced by both current density and electrode geometry. These dynamics govern coalescence behavior and detachment efficiency, thereby influencing overall electrolytic efficiency. A deeper understanding of these mechanisms can enable the rational design of electrodes for improved bubble management and system performance. In this work, the evolution of oxygen bubbles on horizontal wire electrodes was investigated during acid electrolysis using synchronized high-speed imaging and electrochemical measurements. Bubble size distributions were quantified across current densities (0.05–1.0 A·cm^–2) and electrode diameters (100–500 μm). Coalescence dynamics were analyzed through energy and force balance considerations, while electrode performance was evaluated via polarization curves. The findings show that increasing the current density or electrode diameter leads to the formation of larger and more polydisperse bubbles. Coalescence events were predominantly concentrated at the apex of the electrode. Three distinct coalescence-driven dynamics emerged: the coalescence-induced movement mode, the coalescence-induced detachment mode, and the coalescence-induced jumping mode, with each mode governed by bubble radius ratios. Smaller diameter electrodes exhibited higher overpotentials at elevated current densities, underscoring their performance limitations. The results establish correlations between bubble behavior and electrode dimensions, offering valuable insights for designing optimized electrodes that enhance electrolysis efficiency via bubble control.