Numerical Simulation of Water Electrolysis using Comsol Multiphysics

This article presents the results of a numerical simulation of the spatial distribution of electrochemical parameters during water electrolysis in a bipolar cell using the COMSOL Multiphysics software package. The study focuses on analyzing the profiles of current density, H⁺/OH⁻ ion concentrations, and pH along the interelectrode space (0–100% of the distance between the cathode and anode). It was found that an alkaline zone (pH > 10), dominated by OH⁻ ions, forms near the cathode, while an acidic zone (pH < 5), with a predominance of H⁺, forms near the anode. A minimum current density (2.0 mA/cm²)and neutral pH values (7.5) are observed at the cell's center. Identified asymmetries (e.g., higher current density at the anode – 9.2 mA/cm² versus 8.5 mA/cm² at the cathode) are attributed to the thermodynamic complexity of the oxygen evolution reaction. The results are verified by comparison with electrochemical kinetics and ion migration equations, and directions for model optimization (accounting for convection, buffer systems) are identified.