Insight into the electrolyte concentration impact on single hydrogen bubble evolution dynamics at a microelectrode during electrochemical water splitting

Abstract

Bubbles generated during electrochemical water splitting could adhere to the electrode surface and therefore impede the reaction. Thus, understanding and manipulating the evolution dynamics of bubbles is crucial for enhancing electrolysis efficiency. In this study, we investigated the evolution mechanism and forces acting on individual hydrogen bubble on Pt microelectrode surface by employing different H2SO4 electrolyte concentrations (0.2–1.0 M) under various applied voltages [−2 to −6 V vs saturated calomel electrode (SCE)]. We focused on bubble detachment diameter, average current, and bubble lifetime and subsequently established relational equations over these variables. At −6 V vs SCE, the growth coefficient has a maximum value of 14.42 × 10−4 m/s0.333 when the concentration of electrolyte is around 0.6 M. Gas production at 0.6 M increased by 63.4% compared to 0.2 M and by 11.2% compared to 1.0 M. Therefore, choosing the appropriate electrolyte concentration can maximize gas production and bubble detachment efficiency. Additionally, a force balance model incorporating the Marangoni force for single bubbles on the microelectrode surface was established across varying concentrations of H2SO4 electrolyte. At −4 V vs SCE, the solutal Marangoni force starts to dominate when electrolyte concentrations above 0.4 M. The results demonstrate the critical role of the solutal Marangoni force beyond a certain value of electrolyte concentration.