The Impact of Flow Field Design and Mechanical Compression on the Electrochemical Performance in Polymer Electrolyte Membrane Water Electrolysis

The efficiency of polymer electrolyte membrane water electrolysis is influenced by the design of the flow field (FF), which governs fluid distribution, pressure balance, and mechanical contact. Homogeneous mechanical compression is required to obtain effective contact between the anodic porous transport layer (aPTL) and the anodic catalyst layer (aCL), thereby ensuring efficient utilization of the catalyst‑coated membrane (CCM). By testing ten distinct FF designs, including rib‑channel, planar, meander, and block geometries, in a common cell configuration, we find that the performance spread is dominated by variations in high‑frequency resistance (HFR). These HFR differences arise mainly from inhomogeneous cell compression, an effect that becomes pronounced for wide‑channel geometries. Therefore, we evaluate three design strategies to restore high performance with wide‑channel FFs: (i) platinized aPTLs to improve the aPTL‑aCL electrical interface; (ii) stiff Ti‑fiber PTLs on the cathodic side (cPTL) to increase rigidity and homogenize the local mechanical pressure; and (iii) a planar cathodic FF geometry, which likewise homogenizes the mechanical pressure distribution.