Microwave Field Enhancement at Metal‐Electrolyte Interfaces Enables Rapid Growth of Fe‐Ni ₃ S ₂ on Nickel Foam for Alkaline Oxygen Evolution

High‐performance oxygen evolution reaction (OER) catalysts must combine low overpotential, fast electron/ion transport, low‐cost scale‐up production, and long‐term durability under alkaline operation. Although Fe‐doped Ni 3 S 2 is considered a catalyst satisfying the conditions, rapid uniform growth of Fe‐Ni 3 S 2 on metallic Ni supports remains challenging. Herein, we circumvent this long‐standing obstacle by harnessing a localized microwave field enhancement effect at the electrode–electrolyte interface. This strategy enables rapid (15 min) and low‐power (75 W) growth of a highly crystalline Fe‐Ni 3 S 2 catalyst directly on the Ni foam substrate. The as‐synthesized catalyst shows exceptional OER performance, exhibiting a low overpotential of 270 mV at 100 mA cm −2 and outstanding durability for over 100 h. Moreover, the successful operation of an anion exchange membrane water electrolysis device demonstrates its practical feasibility. This study not only unveils a superior OER electrocatalyst but also establishes the principle of microwave field enhancement as a new and powerful paradigm for the energy‐efficient synthesis of functional materials directly on metallic platforms.