A cross-scale numerical framework of PEM water electrolyzer with pore-scale transport properties of PTL

Mismatched microstructure design between the porous transport layer (PTL) and performance requirements in proton exchange membrane water electrolyzer (PEMWE) directly induces local overheating and high overpotential, posing critical challenges to safe and efficient operation. However, there is a lack of methods that integrate the pore-scale electrical, thermal, and mass transport characteristics of the PTL with the macroscopic electrolyzer performance. In this study, a cross-scale numerical framework based on ANSYS Fluent and CFD code is proposed coupled with PTL transport characteristics, enabling a comprehensive evaluation of both microscopic and macroscopic performance for electrolyzers incorporating different PTL structures. Based on the framework, the effects of different PTL structural parameters on electrolyzer performance are analyzed from the perspectives of transport coefficients, contact resistance, and two-phase evolution. Results show that increasing fiber diameter from 20 μm to 60 μm improves mass transfer but significantly reduces thermal conductivity and electronic conductivity in the through-plane, with anisotropy ratios rising from 2 to 5. Additionally, oxygen transport in the PTL is jointly determined by local bubble nucleation sites and pore characteristics of the PTL, requiring 16.9 ms for Oxygen breakthrough through the last fiber layer. Furthermore, a PTL selection spectrum of different fiber diameters and porosities is reported by integrating the microscopic PTL transport characteristics with the macroscopic multi-physical performance of electrolyzers. The spectrum includes 5 control regions and a lower cell voltage of 2.12 V at 2 A/cm² can be achieved in the neutral region. This study is expected to provide helpful guidelines for the targeted design of PTL structures and the performance optimization for future large-scale electrolyzers.