Isotypic γ-γ Integration of γ-FeOOH on Electrochemically Reconstructed NiFeOOH Nanosheets: Unlocking Interfacial...

Anion exchange membrane water electrolysis (AEMWE) holds great promise for green hydrogen production, yet its widespread adoption is hindered by the inadequate activity and stability of non-precious electrocatalysts under industrial conditions. Here, we report an isotypic γ-γ heterostructured NiFeOOH-γ-FeOOH catalyst grown on nickel foam (NiFeOOH-γ-FeOOH/NF) via a dual-phase architecture strategy. The γ-phase NiFeOOH is pre-constructed via an electrochemical treatment of NiFe layered double hydroxide, and subsequently the epitaxial-like growth of γ-FeOOH on its surface forms a coherent γ-γ heterointerface. This integration synergistically enables the modulation of the oxidation states and coordination environments of Fe and Ni, leading to the identification of the uncoordinated Fe and Ni sites with high oxidation states as the primary active sites. The optimized NiFeOOH-γ-FeOOH/NF electrode exhibits excellent oxygen evolution reaction performance, achieving a low overpotential of 208 mV at 10 mA cm^-2 in 1 M KOH. Furthermore, the NiFeOOH-γ-FeOOH/NF assembled AEMWE device delivers an industrial-level current density of 500 mA cm^-2 at 1.85 V and 65°C, maintaining stable operation for over 360  h. This study offers novel insights into the stabilization and activity enhancement of NiFe-based electrocatalysts, highlighting their potential to advance green hydrogen production under industrial-level current densities.