Layered‐Hierarchical Dual‐Lattice Strain Suppresses Ni x Se Surface Reconstruction for Stable OER in Alkaline Fresh/Seawater Splitting

Abstract Transition metal selenides (TMSe) are promising oxygen evolution reaction (OER) electrocatalysts but act as precursors rather than the actual active phase, transforming into amorphous oxyhydroxides during OER. This transformation, along with the formation of selenium oxyanions and unstable heterointerfaces, complicates the structure‐activity relationship and reduces stability. This work introduces novel “layered‐hierarchical dual lattice strain engineering” to inhibit the surface reconstruction of Ni x Se by modulating both the nickel foam (NF) substrate with Mo 2 N nanosheets (NM) and the Ni x Se nanorods‐nanosheets catalytic layer (NiSe‐Ni 0.85 Se‐NiO, NSN) with ultrafast interfacial bimetallic amorphous NiFeOOH coating, achieving the optimized NM/NSN/NiFeOOH configuration. The NM substrate induces lattice strain, enhancing OER activity by improving electron transport and adhesion, while the NiFeOOH coating induces additional lattice strain, mitigating the surface reconstruction and oxidative degradation, reinforcing structural integrity. The NM/NSN/NiFeOOH catalyst demonstrates exceptional OER performance with low overpotentials of 208 mV@10 mA cm −2 and outstanding stability over 100 h at 100 mA cm −2 in alkaline freshwater and seawater. Theoretical analysis shows that NiFeOOH effectively prevents surface reconstruction and oxidative degradation by preserving Ni sites for optimal OER intermediate interactions while stabilizing the electronic environment. This work provides a novel strategy for enhancing the OER stability of TMSe and beyond.