Comparative Analysis of Fiber-Based and Powder-Based Porous Transport Layers in Water Electrolysis for Green Hydrogen

In this work, sintered titanium powder porous transport layers (PTLs) and titanium fiber PTLs are systematically investigated and compared. The stochastic reconstruction method for 3D PTLs, morphological and topological characterization, pore-scale modeling (PSM), and Lattice Boltzmann method (LBM) are employed to comprehensively examine the bulk properties, surface properties, transport parameters, and oxygen removal for two types of PTLs. A parametric PTL matrix consisting of two types of PTLs, each with different mean pore sizes and porosity, is selected for analysis. The results illustrate the substantial difference for the properties obtained for PTLs depending on the material and structural characteristics. Powder PTLs feature more homogeneous structural and transport properties (electrical and thermal conductivity) in comparison to fiber PTLs. PTLs with lower porosity and lower mean pore size exhibit superior surface properties and higher electrical and thermal conductivity but are not favorable for efficient oxygen removal. In order to weigh the kinetic overpotential, ohmic overpotential, and mass transport overpotential, double-layer PTLs are constructed with the aim of balancing interfacial contact, electrical and thermal conductivity, and oxygen transport. The impact of the thickness ratio is elaborated and further optimization strategies are also provisioned. This work provides insights and references for a better understanding of the properties of PTLs and offers practical guidelines for the design and application of PTLs in commercial large-scale water electrolyzers.