Performance modeling and mechanism study of proton exchange membrane water electrolyzer coupled with water electroosmosis

[Display omitted] •A full-scale two-phase model is developed and verified by experimental data for electrolyzer.•Water electroosmosis is coupled in the model to conduct the mechanism analyses.•Characteristic distributions of mass transport are studied via different perspectives.•Explanation for the heat transfer law of porous transport layer by temperature distribution.•Theoretical analysis of the impacts of influence factors on the ohmic resistance is conducted. Proton exchange membrane water electrolyzers are highly promising green and high-purity hydrogen production devices. Cell performance and characteristic distribution are influenced by complex multiphysics processes, such as two-phase flow and water electroosmosis; however, detailed mechanistic analyses and influencing factors have not been thoroughly studied. A three-dimensional full-scale two-phase model, which couples the hydrodynamics, electrochemical reaction kinetics, mass and heat transfer, two-phase flow based on capillary pressure, and water electroosmosis, was developed and verified using experimental data in this study. The effects of cell voltage on heat and mass distribution were discussed in detail for multiple coupled physical processes. Three crucial parameters, porous transport layer porosity, thickness, and membrane type, were investigated regarding their effects on the characteristic distribution and cell performance. Finally, an ohmic resistance analysis was conducted to investigate the impact of the physical properties of the material. The results show that the increased porosity and decreased thickness of porous transport layer positively improved the mass transport and current density and decreased interfacial contact resistance. Consequently, the water discharge in the cathode was improved accordingly. Moreover, the membrane type is closely related to water electroosmosis owing to the different electroosmosis coefficients, and the reduced membrane thickness decreased the proton exchange membrane resistance. This study lays the foundation for further mechanistic analyses of mass and heat transfer, water management on the cathode side, and performance optimization in electrolyzer.