Proton exchange membrane water electrolysis at high current densities: Response time and gas-water distribution

Understanding the distribution of oxygen in proton exchange membrane water electrolysis (PEMWE) is crucial for improving electrolysis efficiency and gas removal. In this study, we developed a two-dimensional (2D) transient model that couples the Euler-Euler multiphase model with electric potential equations to investigate two-phase flow in PEMWE. Our simulation reveals that the system's response time initially decreases and then increases with current density, indicating longer response times at high current densities. Modifying the wetting properties of the porous transport layer (PTL) affects gas removal at low gas holdup, resulting in a maximum 15% decrease in gas holdup. However, at high gas holdup, the flow field in the channel predominantly governs bubble removal, making changes in PTL wetting properties less influential. With increasing gas production rate, an inverse gradient distribution of gas saturation appears, leading to uneven gas saturation and hindering efficient oxygen removal. This non-uniform gas saturation adversely affects electrolysis performance.