Interplay of Cell Configuration and Performance in Flow Field-Free Alkaline Electrolyser: Optimization of porous Transport Layer and Interlayers

Herein the impact of porous transport layer (PTL) structure, interlayer design and materials, and operating conditions on the performance and durability of anion exchange membrane water electrolyzers (AEMWEs) is thoroughly investigated. By using nickel felt PTLs with 250 µm and 450 µm thicknesses, and interlayers such as Ni mesh, Inconel 600, wire-sintered stainless steel (W-S SS), and wire-sintered nickel (W-S Ni), we systematically examined how mechanical compression affect membrane electrode assembly at low and high current densities. Electrochemical analyses demonstrated that the AEMWE cell assembled with the 450 µm Ni felt maintains its performance under high external pressures (10–20 bar), while nickel felt 250 µm performance deteriorate at high current density (e.g ˃ 1.5 A.cm^-2). Secondary interlayers significantly improved the initial performance by reducing interfacial contact resistance. However, long-term stability diverged among materials where W-S SS and Inconel suffered from degradation and increased resistance over time, likely due to oxidative passivation in the anode compartment of the AEMWE single cell. On the contrary, when W-S Ni is used as interlayer superior initial performance will maintain and degradation rate of just 0.18 mV.h^-1 over 160 hours at 0.5 A.cm^-2 in 1 M KOH at 50 °C is observed. Postmortem inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis revealed undetectable Ni leaching and moderate Fe dissolution from OER catalyst, i.e. NiFeO_x, in the anode compartment. These findings demonstrate the critical role of tailored interlayer and PTL configurations to achieve high-performance and stable AEM water electrolyzer operation under pressurized conditions and high current densities.