Effect of electrode structure on the energy efficiency and minimum load operation for pressurized alkaline water electrolysis: A numerical study

Traditional anodic hydrogen mitigation in alkaline water electrolysis (AWE) cells focuses on enhancing separator material properties to resist hydrogen permeation while maintaining ion conductivity. In this study, we explore an alternative strategy utilizing a physically rigorous multi-field CFD model: customizing structural properties of Ni foam electrodes – porosity, thickness, and surface roughness - to manage hydrogen crossover and enhance overall performance. The model offers valuable insights into the interplay between electrode design and internal multiphysics phenomena. Simulation results reveal that electrode structure significantly affects hydrogen contamination. Specifically, a differential porosity configuration reduces hydrogen to oxygen (HTO) crossover by approximately 40 % compared to the baseline case, lowering the minimum safe operating current density by 80 %. While this operational improvement is energetically unfavourable, increasing energy consumption by about 0.6 % vis-à-vis the baseline case at high currents, the study identifies an optimum pore configuration that balances cell energy efficiency and operational flexibility. This approach introduces a new reliability and safety perspective to electrode design, enabling greater operational flexibility in fluctuating renewable energy environments. Ultimately, this work guides the development of innovative strategies taking a substantial step towards practical integration of alkaline electrolyzer in a carbon-free power generation paradigm.