Evolution of hydrogen bubbles on a microelectrode driven by constant currents and its impact on potential response

• Overpotential shifts from activation dominance to ohmic dominance. • Peak voltage U 0 , valley U 1 and Δ U increase proportionally with bubble detachment radius. • Study of applied current and electrolyte concentration effects on bubble evolution. • A balance of forces was established to clarify hydrogen bubble detachment behavior. • Ohmic overpotential scales with bubble size and activation scales with contact size. To understand the relationship between electrolytic hydrogen bubble evolution and electric potential fluctuations, a synchronized measurement system, comprising a high-speed camera and an electrochemical workstation, was employed to analyze single hydrogen bubble evolution on a microelectrode and investigate the voltage–time characteristics of a typical hydrogen evolution reaction. The results show periodic potential fluctuations caused by the periodic evolution of single hydrogen bubbles. The overpotential fluctuation during single bubble evolution exhibits two stages: an initial increase (Stage I) followed by a decrease (Stage II). The duration of Stage I decreases with increasing applied current. Subsequently, a balance of known forces was developed to clarify the critical roles of the Marangoni effect and electric force in bubble detachment dynamics, enabling the prediction of bubble detachment size. Furthermore, it was observed that, during single bubble evolution, the overpotential shifts from activation dominance to ohmic dominance. The magnitude of ohmic overpotential correlates with the bubble diameter, whereas activation overpotential correlates with the bubble’s contact diameter. This study contributes to the understanding of activation and ohmic overpotentials linked to bubble evolution in water electrolysis devices, thereby facilitating the development of more efficient multiphase electrochemical reactors.