Synergistic coupling of Ni-oxalate prism and layered FeOOH for oxygen evolution reaction in anion exchange membrane water electrolysis

Hydrogen production in anion exchange membrane water electrolyzers (AEMWE) is significantly hindered by the challenges associated with the oxygen evolution reaction (OER). This anodic half-reaction requires a high overpotential and relies on costly precious metal-based electrocatalysts. This study introduces a novel OER electrocatalyst, layered FeOOH anchored on three-dimensional Ni oxalate prisms (FeOOH@NOP), synthesized via straightforward chemical bath deposition and electrodeposition methods. The FeOOH@NOP exhibits superior OER performance with a low overpotential of 336 mV at 100 mA cm^–2, along with remarkable operational durability over 100 hours without any noticeable degradation in electrochemical activity. We investigated the adsorption site of OER intermediates on FeOOH@NOP utilizing in-situ X-ray absorption near edge structure and density functional theory calculations. We found that coupling NOP and FeOOH synergistically maintains the structural integrity, while the NOP inner layer enhances the OER activity on the FeOOH (the primary active sites) by stabilizing terminal oxo intermediates. The FeOOH@NOP achieved the superior hydrogen production rates in AEMWE with remarkable current density of 3.4 A cm^–2 at V_cell of 2.01 V, even compared to the benchmark Ir black and recently reported MOF-based anode materials. These results underscore its promising scalability and practical applicability for hydrogen generation.