Operando Electrochemical Formation of Integrated Ni-Fe Oxyhydroxide Anode for Durable Anion Exchange Membrane Water...

Efficient hydrogen production via anion exchange membrane water electrolyzers (AEMWEs) requires electrocatalysts that exhibit both high performance and long-term stability under industrially relevant current densities. While Ni-Fe-based catalysts have emerged as promising candidates for the oxygen evolution reaction, their practical implementation in AEMWEs is still limited by multistep ex situ fabrication and, in many cases, by the poor interfacial stability of particle-based catalyst layers. Here, we report an operando electrochemical strategy to directly construct integrated (Fe, Ni)OOH catalysts on Ni foam anodes via voltage-cycling in a FeOOH-containing electrolyte. This one-step operando activation enables rapid and scalable fabrication of integrated electrodes in a practical electrolyzer device, eliminating the need for binders, slurry casting, and post-annealing. The voltage cycling in the FeOOH-containing electrolyte induces simultaneous Ni oxidation and Fe adsorption, leading to the formation of a porous, defect-rich Ni-O-Fe structure with enhanced conductivity and catalytic activity. The resulting integrated electrode delivers a high current density of 2.8 A cm^-2 at 1.8 V and operates stably for over 7000 h in a two-cell AEMWE stack, without significant catalyst delamination. This work provides a simple, efficient, and scalable route for developing durable, non-precious metal-based anodes for AEMWEs.