Multifaceted Roles of the Fe/Ni Ratio in Regulating Reconstruction Chemistry of NiFe Selenide Precatalysts for Anion Exchange Membrane Water Electrolysis

Developing efficient and durable oxygen evolution catalysts is vital for advancing anion exchange membrane water electrolysis (AEMWE). Herein, a series of Ni1−xFexSe (x = 0.1, 0.25, and 0.5) nanorod arrays with tunable Fe/Ni ratios were synthesized through one-step selenization of commercial Ni-Fe foams to uncover the intrinsic influence of Fe content on activity and stability. The optimized Ni0.75Fe0.25Se achieves an ultralow OER overpotential of 302 mV at 1000 mA cm−2 with negligible degradation over 500 h. When employed as the anode in an AEM water electrolyzer, the Ni0.75Fe0.25Se/NIF electrode delivers a low cell voltage of 1.73 V at 1000 mA cm−2 and maintains stable operation for over 1300 h with an ultralow voltage decay rate of 54 μV h−1. Structural and spectroscopic analyses demonstrate that a moderate Ni/Fe ratio effectively optimizes the electronic structure of Ni1−xFexSe, while the in situ formed interfacial interlayer markedly enhances structural robustness. More importantly, the Fe/Ni ratio dictates the electrochemical reconstruction of Ni1−xFexSe precatalysts into active NiFeOOH under practical AEMWE conditions, while moderate Fe incorporation promotes well-controlled reconstruction, balances defect chemistry, optimizes the electronic structure, and thereby enhances both intrinsic OER activity and long-term stability.