Engineering Local Charge Reconfiguration in NiMoO₄·xH₂O Nanosheets for High-Activity OER Catalysis under...

The oxygen evolution reaction (OER) is central to electrochemical water splitting but remains constrained by sluggish kinetics and catalyst degradation under harsh oxidative conditions. Although many nonprecious electrocatalysts exhibit promising activity at low current densities (10 ∼ 50 mA cm^-2), attaining industrially relevant performance is still impeded by inefficient charge transport and unfavorable adsorption of OER intermediates, particularly at high current densities (∼500 mA cm^-2). Herein, we develop a dual-step hydrothermal strategy to construct ultrathin NiMoO₄·xH₂O nanosheets on 3D nickel foam, followed by controlled Fe incorporation through ion-exchange-driven surface reconstruction. Consequently, the Fe-NiMoO₄·xH₂O electrode achieves an industrial-related current density of 500 mA cm^-2 at a low overpotential of 305 mV with excellent long-term stability. In situ Raman spectroscopy reveals that Fe incorporation promotes the surface reconstruction of NiMoO₄·xH₂O into the catalytically active NiFeOOH phase under OER conditions. Density functional theory (DFT) calculations further demonstrate that, among various 3d transition-metal dopants in the NiMoO₄ lattice, Fe incorporation gives the most thermodynamically stable configuration and the most favorable electronic structure. The resulting local electronic reconfiguration generates Fe-3d-enriched frontier states near the Fermi level (-0.5 to 0 eV), thereby facilitating charge transfer and optimizing the adsorption of OER intermediates. Overall, the integrated structural-electronic modulation optimizes the local atomic environment and accelerates OER kinetics, underscoring local charge engineering as an effective strategy for industrial-grade OER.