Impact of Gas Bubble Evolution Dynamics on Electrochemical Reaction Overpotentials in Water Electrolyser Systems

Abstract

This study establishes a theoretical framework to elucidate the impact of gas bubble evolution dynamics on the reaction overpotentials in electrolytic hydrogen and oxygen production. By distinguishing between ohmic, activation, and concentration overpotentials, we formulate governing equations to determine the influence of gas bubble growth and detachment on each overpotential component. Additionally, we employ SHapley Additive exPlanations (SHAP) analysis to interpret the patterns identified by a regression neural network trained on our analytical equations. Our findings indicate that gas bubble evolution dynamics impact reaction overpotentials to different degrees, leading to divergent escalation rates and requiring targeted improvement strategies. We therefore systematically investigate the impact of key parameters influencing the gas bubble evolution dynamics such as the electrode surface wettability, the electrolyte concentration and the temperature on mitigating reaction overpotentials. Measures, such as enhancing the electrode hydrophilicity from 90 to 160°, reduces the activation and concentration overpotentials by up to 54.0% and 79.3%, respectively. Moreover, by increasing the electrolyte molarity from 0.5 to 1 M, ohmic and concentration overpotentials can be reduced by 47.1% and 72.1%, respectively, with diminishing performance returns beyond 2 M. Higher temperatures result in mild to moderate decreases across all overpotential components by improving electrolyte conductivity and mass transfer. In summary, this analysis provides valuable insights not only for optimizing electrolytic hydrogen and oxygen production devices, but it also offers the opportunity to transfer gained insights into other gas-evolving electrochemical systems and supports their optimization toward higher energy conversion efficiencies.