Self-Catalyzed Hastelloy Fiber Paper (HAP) Porous Transport Layer for Oxygen Evolution Reaction in Anion Exchange Membrane Water Electrolysis

Abstract Hastelloy fiber paper (HAP) can be used as the oxygen evolution reaction porous transport layer (PTL) without using a catalyst layer in anion exchange membrane water electrolysis. It is combined with Ru on nickel fiber paper (NFP) (hydrogen evolution reaction PTL) to form an asymmetric Ru/NFP(−)//HAP(+) single-cell system. The experimental results for electrodeposited Co(OH)2 on HAP are also demonstrated for comparison. At 70 °C, the cell delivers 725.67 mA cm–2 at 1.8 V under cathode-wet conditions and maintains 701.34 mA cm–2 under cathode-dry operation. A 5000-cycle accelerated stress test (AST) confirms the good operational stability of the system under dynamic cycling conditions. In addition, the effect of Co(OH)2 electrodeposition on the HAP anode was further investigated to show the current density decreases to 485.59 mA cm–2 at 1.8 V when operated at 70 °C. The AST stability also degrades with Co(OH)2 deposition. Further analysis indicates that the electrodeposited Co(OH)2 coating may alter the pore structure and surface wettability of the catalyst layer, leading to mass-transport limitations at high current densities, including hindered ion transport and inefficient oxygen bubble removal.