Establishing The Link Between Flow Uniformity and Overpotential in Electrocatalytic Flow Cell

Hydrogen production through water electrolysis is a cornerstone of sustainable energy strategies, especially when powered by renewable electricity. Among the different technologies, flow cell electrolysers employing foam electrodes offer promising scalability and efficient gas removal. However, the relationship between electrolyte flow uniformity and electrochemical performance remains underexplored. In this work, we investigate the influence of flow uniformity on the overpotential in electrocatalytic flow cells by combining Computational Fluid Dynamics (CFD) simulations with experimental electrochemical measurements. Three flow cell geometries—labeled short, medium, and long—were designed to achieve varying degrees of flow uniformity at the electrode interface. CFD simulations were conducted using OpenFOAM to quantify the velocity distribution across the electrode plane, introducing a Velocity Uniformity Coefficient (VUC) as a metric to evaluate flow homogeneity. The prototypes were fabricated via stereolithography and tested using Ni-Fe oxyhydroxide and Ni oxyhydroxide catalysts for oxygen and hydrogen evolution reactions, respectively. Electrochemical performance was assessed using chronopotentiometry and I-V curves at high current densities (up to 4.5 A), revealing a strong correlation between VUC and overpotential. Designs exhibiting higher flow uniformity (lower VUC) demonstrated significantly lower overpotentials, indicating more efficient catalytic activity. Notably, the “long” design achieved the lowest VUC and best electrochemical performance. Our findings establish a clear link between hydrodynamic conditions and cell efficiency, offering a practical framework for optimizing flow cell designs. By correlating CFD-derived metrics with electrochemical outcomes, this study paves the way for rational design of scalable water electrolysis systems, advancing the implementation of green hydrogen technologies.