A Hierarchical FeOOH/NiMoO ₄ Heterostructure with Reconstruction-Based Interface Design for Durable Alkaline Oxygen Evolution

Achieving high activity together with long-term durability remains a central challenge in the development of non-noble-metal anodes for alkaline oxygen evolution. Here, we report a hierarchical FeOOH/NiMoO 4 electrode on nickel foam constructed through a topology-directed strategy for durable alkaline OER. Under anodic polarization, the outer FeOOH layer undergoes surface reconstruction toward a Ni-containing oxyhydroxide-rich surface, while the underlying NMO-supported framework appears to support interfacial electron transport and structural retention. This structural configuration enables both rapid OER kinetics and robust operation. In 1.0 M KOH, the FeOOH/NiMoO 4 electrode requires an overpotential of 224 mV to reach 10 mA cm –2 and remains stable for over 100 h at 100 mA cm –2 . Potential-dependent in situ Raman spectroscopy in 1.0 M KOH reveals the emergence of γ-NiOOH species during activation, and density functional theory calculations based on a Ni(Fe)OOH/NMO interfacial model suggest more favorable electronic structure and OER energetics after reconstruction. As an auxiliary evaluation of electrolyte adaptability, the electrode also sustains stable operation for over 600 h at 200 mA cm –2 in simulated alkaline seawater (1.0 M KOH + 0.5 M NaCl). In a two-electrode electrolyzer operated in the same electrolyte, stable operation is sustained at 400 mA cm –2 for 200 h. These results highlight reconstruction-based interface design as an effective route to durable alkaline OER anodes, with additional validation under simulated alkaline seawater conditions.