Boosting water back-diffusion in dry-cathode AEMWE for high-current-density hydrogen production

Abstract

Dry-cathode operation is considered an ideal operating mode for AEMWE. However, water management is challenging under such conditions. Previous numerical studies have primarily focused on both-fed configurations, while comprehensive multiphysics investigations of water transport under dry-cathode operation are limited. Herein, a two-dimensional multiphysics model was developed to elucidate the underlying water transport mechanisms and identify effective optimization strategies. The model was systematically validated against experimentally measured polarization curves and electrochemical impedance spectroscopy data. The results indicate that the dry state of the cathode and increased overpotential at high current densities are primarily caused by the imbalance between water back-diffusion and water consumption by the HER. Parametric analysis showed that reducing the membrane thickness from 100 to 60 μm, raising the cathode ionomer content from 0.2 to 0.7, and increasing the aCL porosity from 0.1 to 0.5 enhanced water transport. Moreover, anode pressurization from 1 to 5 atm promoted water back-diffusion, resulting in a 14.3% increase in current density at 2 V. Based on sensitivity-guided synergistic optimization of structural and operating parameters, the optimized AEMWE achieves a current density of 3.26 A cm −2 at 2 V, representing a 52.1% improvement over the baseline. These findings provide mechanistic insights and practical guidance for optimizing water management in dry-cathode AEMWE.