Coupling morphological evolution and multiphase transport to Decipher degradation in PEM water electrolyzers

• A multiphysics model that couples level set geometry evolution with PEMWE performance simulation is developed. • Morphological changes in the PTL are linked to transport losses and voltage degradation. • Model predictions are validated against experimental polarization curves and bubble behavior. • Long-term degradation trends and voltage increases are accurately reproduced. • The framework connects material aging to performance loss, supporting the design of durable electrolyzers. In this work, we present a multiphase numerical model for the corrosion degradation of proton exchange membrane water electrolyzers. The numerical framework comprises two main components, a geometry tracking component and a performance evaluation component. The geometry tracking is based on the Level Set method that models the evolution of the geometry due to the deposition or erosion of corrosion products in the porous transport layer along the lifecycle of the device given a specified corrosion rate. The performance of the device at each time step is evaluated using a multiphase model with the Navier-Stokes equation for the two-phase mixture, and a transport equation for a dispersed phase of bubbles in the continuous water phase. Catalyst layer degradation is included through appropriately chosen boundary conditions in the geometry. This integrated approach allows the model to directly link structural changes in the porous transport layer to evolving transport phenomena and the overall electrochemical performance of the device. The corrosion process is introduced through an effective corrosion velocity, which provides a phenomenological description of PTL degradation rather than a mechanistic prediction based on local electrochemical conditions. Thus, the framework should be considered a multiphysics tool that propagates assumed degradation scenarios to device-scale performance rather than a first-principles corrosion model.