Correlating Flow Field Geometry and Porous Transport Layer Properties for Efficient PEM Water Electrolysis

In this work, three commercial, titanium fiber- or powder-based porous transport layers (PTLs) for polymer electrolyte membrane water electrolysis (PEMWE) are characterized in terms of pore size, porosity, surface roughness, and in-plane permeability. The latter is quantified using an in-house designed setup, revealing a nearly 10-fold higher permeability for fiber compared to powder-based PTLs. PEMWE polarization curves and high-frequency resistances are recorded with 5 cm² single-cells with serpentine flow fields (FFs), comparing the performance of the three anode PTLs in dependence of the anode FF land width (ranging from 0.7–6.2 mm; with a constant channel width and depth of 1 mm). A detailed voltage loss analysis reveals the absence of significant mass transport resistances at the anode side at low to moderate current densities, even when using the anode FF with the largest land width in combination with the PTL with the lowest permeability. In contrast, at high current densities (>2 A cm⁻²), the combination of large anode FF land width and low-permeability PTL leads to significant mass transport related performance losses, accompanied by a local dry-out of the membrane and a reduced MEA utilization, which can be rationalized by a simple model.