Modeling Two-Phase Transport on the PEM Water Electrolyzer

Understanding multi-phase and multi-component transport in a porous electrode plays a crucial role in optimizing the actual electrode structures and maintaining the performance of a polymer electrolyte membrane (PEM) water electrolyzer, which has attracted more attention for renewable energy storage and hydrogen production due to its higher efficiency/density and a more compact design. Since the electrode microstructure and transport mechanisms of a PEM water electrolyzer is quite complex, until recently, it has been very difficult to provide a comprehensive understanding of these mechanisms. Although some experiments and few simple numerical models have been carried out for investigating the two-phase  transport phenomena in a PEM water electrolyzer, many fundamental issues still remain, particularly concerning the effects of gas-liquid two-phase  transport inside porous liquid/gas diffusion layer (LGDL) with various surface wetting properties, pore structures on the electrolyzer performance.

In this study, a comprehensive two-phase transport model has been developed as an efficient numerical scheme for direct modeling the effects of two-phase  transport on the electrolyzer performance, particularly for liquid water and oxygen transport in the anode porous gas diffusion layer. The liquid water saturations are found to decrease significantly along the LGDL thickness direction with larger contact angles. But for smaller contact angles, the saturation values along the LGDL thickness direction are almost identical. Further numerical results for the gas-liquid two-phase transport behaviors and electrolyzer performance with effects of LGDL pore morphology will also be presented. Results obtained from the present model will provide fundamental understandings of gas-liquid transport behaviors in a porous electrode and can be employed as the useful information to design and optimize the electrode microstructure and improve the performance of PEM water electrolyzers.