Investigating the bubble formation phenomenon in alkaline water electrolysis for enhanced hydrogen production

Efficient hydrogen production via alkaline water electrolysis is often limited by the accumulation of gas bubbles on electrode surfaces, which reduces the available active area and increases energy losses. Developing strategies to mitigate this issue requires a comprehensive understanding of bubble-related phenomena. To support such understanding, this paper examines the multi-phase dynamics of hydrogen evolution through detailed computational analysis, focusing on interrelated aspects of electrode bubble behaviour including coalescence, detachment, and gas volume fraction (GVF). Three complementary studies were conducted to provide an integrated comprehensive view of bubble dynamics: (1) bubble coalescence and transport under varying inter-bubble gaps and flow velocities, (2) bubble detachment characteristics across five electrode morphologies with differing surface features, (3) GVF distributions and trends as a function of applied voltage, electrolyte temperature, concentration, and membrane thickness. Results showed that nanostructured surfaces promote earlier bubble detachment, while narrower inter-bubble gaps and mild forced convection enhance bubble coalescence. The parametric analysis confirmed that GVF increases with applied voltage, electrolyte temperature, and KOH concentration, but decreases with membrane thickness for the investigated geometry and operating range. To complement these findings, a multiple linear regression modelling approach based on scaled electrochemical dimensionless groups is proposed. The developed model predicts GVF with high accuracy (adjusted R 2 = 0.974 ), offering a fast and scalable alternative to repeated analysis. Overall, this work provides both a mechanistic understanding of factors affecting bubble dynamics in alkaline hydrogen production and proposes a predictive modelling approach to support the optimisation of electrolyser design for enhanced performance.