Optimizing Porous Transport Layer Design Parameters via Stochastic Pore Network Modelling: Reactant Transport and Interfacial Contact Considerations

In this work, we designed sintered titanium powder-based porous transport layers (PTLs) for polymer electrolyte membrane (PEM) electrolyzers by tailoring the powder diameter and porosity via a new approach. We examined how the PTL powder diameter and porosity influence reactant transport and PTL-catalyst layer (CL) interfacial contact by using a stochastic generation model combined with a pore network model. We enhanced reactant transport by increasing powder diameter and porosity, as shown through increases in single- and two-phase permeabilities of liquid water. Compared to the impact of increasing the powder diameter, increasing the PTL porosity dominated the impact on permeability of liquid water. However, we observed a trade-off to the benefits of increasing the powder diameter such that larger powders led to a higher surface roughness at the PTL-CL interface. From this work, we recommend that the PTL powder diameter and porosity must be strategically selected for the desired target operating conditions of the PEM electrolyzer. We recommend a PTL with d _P = 25 μm and ε = 26.5% for an electrolyzer cell operating at non-starvation conditions, and a PTL with d _P = 25 μm and ε = 40.5% for an electrolyzer cell operating at starvation conditions.