Modeling and Experimental Validation of Bubble-Induced Performance Losses in Microstructured Copper Electrodes for Alkaline Water Electrolysis

Abstract

Water electrolysis is a promising technology for sustainable hydrogen (H$_2$) production. However, gas bubble formation significantly degrades the electrochemical surface area ($A_{\rm EC}$) and the electrocatalytic activity of microstructured electrodes in water electrolyzer cells. Existing theoretical models fail to connect computational fluid dynamics (CFD) and electrochemistry to analyze how bubble dynamics affect the performance of gas-evolving microstructured electrodes. This work develops a multiphysics-based theoretical model that couples two-phase CFD with Butler-Volmer and Faradaic kinetics, incorporating exchange current density, cell current, gravitational acceleration, surface tension, and fluid properties such as density and viscosity. The model quantifies essential electrochemical parameters, such as the enhancement in $A_{\rm EC}$ and the overpotential ($η$), which deviate by less than 7\% and 15\%, respectively, from the experimental results. Evaluations of the fabricated microstructured electrodes using polarization curves, cyclic voltammetry, electrochemical impedance spectroscopy, and linear polarization resistance techniques demonstrate reduced $η$ by 2.49--21.39\% and 9.55--24.32\% for oxygen (O$_2$) and H$_2$ evolution, respectively. Furthermore, the model reveals the interplay between enhanced geometric surface area and bubble-transport limitations, facilitating the optimization and analysis of structural parameters. These findings establish a physics-informed roadmap for designing optimal, robust, and industry-scalable microstructured electrodes for efficient H$_2$ generation via water electrolysis.