Transient‐Promoter‐Stabilized NiFe Oxyhydroxide Enables Durable kW‐Scale Water Splitting Under Fluctuating Power

Abstract Renewable‐powered water electrolysis provides a carbon‐neutral route to hydrogen, yet large‐scale deployment is constrained by reliance on stable but carbon‐intensive grid electricity. Direct integration with fluctuating renewable power requires catalysts and devices that can endure dynamic operating conditions. Here we present a transient‐promoter strategy for NiFe oxyhydroxide oxygen evolution reaction (OER) catalysts, realized from Ni 3 Fe 1.2 Cr 0.8 O x precursor, for kilowatt‐scale anion exchange membrane water electrolyzers (AEMWEs). Ex situ and operando spectroscopy establish that Cr (i) modulates Ni/Fe oxidation states to enrich positive charge and facilitate oxyhydroxide formation, (ii) induces porosity that enhances electrolyte penetration and OH − adsorption, and (iii) leaches sacrificially to protect Ni/Fe active sites. Lab‐scale AEMWE device achieves an industrially relevant current density of 1 A cm − 2 at a cell voltage of 1.68 V and sustains continuous operation for over 30 days under both constant and fluctuating loads. Scaling from 1 cm 2 AEMWE to an 8‐cell, 512 cm 2 stack, the system can handle an electrical power of 2.5 kW at peak, and delivers 1 A cm − 2 at 1.78 V per cell at 60 °C. The stack remains resilient over 13 simulated solar cycles (>50 h), underscoring the feasibility of integrating renewable electricity with durable, NiFe oxyhydroxide OER catalyst based AEMWEs.