Real‐Time Monitoring of Fe‐Induced Stable γ‐NiOOH in Binder‐Free FeNi MOF Electrocatalysts for Enhanced Oxygen Evolution

Abstract Hydrogen energy is a promising renewable source, and metal‐organic frameworks (MOFs) are considered potential electrocatalysts for water electrolysis due to their abundant active sites, high porosity, and large surface area. The synthesis of bimetallic iron‐nickel‐benzene‐1,3,5‐tricarboxylate/nickel foam (FeNi‐BTC/NF) MOF is reported using a binder‐free one‐pot method by immersing nickel foam (NF) into a solution of benzene‐1,3,5‐tricarboxylic acid (BTC), N,N‐dimethylformamide (DMF), and iron (Fe) salts. FeNi‐BTC/NF exhibits a low overpotential of 276 mV at 100 mA cm − 2 , a Tafel slope of 94 mV dec −1 , and stability exceeding 120 h. The Fe‐Ni interaction facilitates the formation of a stable gamma‐nickel oxyhydroxide (γ‐NiOOH) phase, preventing its reversion to nickel hydroxyide (Ni(OH)₂), which is crucial for improving oxygen evolution reaction (OER) performance. This phase transition, revealed via in situ Raman spectroelectrochemical analysis, enhances electrocatalytic activity. Additionally, high‐valent Fe modulates the electronic structure of Ni, enabling FeNi‐BTC/NF to transform into γ‐NiOOH at higher potentials, with Fe and γ‐NiOOH synergistically boosting OER efficiency. The findings offer insights into Fe/Ni atom interactions and phase transformations in FeNi‐BTC/NF MOFs for enhanced water splitting.