FeCoP Nanosheets Synthesized from FeCo Layered Double Hydroxides as Catalysts for the Oxygen Evolution Reaction

The development of efficient and stable electrocatalysts for the oxygen evolution reaction (OER) is crucial for sustainable energy conversion. Herein, we report the synthesis of FeCo-layered double hydroxides (FeCo-LDHs) and FeCo phosphide (FeCoP) freestanding electrodes on nickel foam via hydrothermal and phosphorization methods. The FeCoP/NF electrode demonstrates superior OER performance compared to FeCo-LDH/NF, exhibiting a lower onset potential (1.35 V vs RHE), higher current density (1000 mA cm –2 ), and a smaller Tafel slope (60.4 mV dec –1 ), indicating enhanced reaction kinetics. Chronoamperometry tests reveal exceptional stability, with negligible activity loss after 75 h of operation. Using scanning electrochemical microscopy (SECM) feedback mode, the kinetic coefficient of the optimized FeCoP/NF electrode is 1.51 × 10 –2 cm 2 s –1, and the SECM substrate-tip collection (SG-TC) mode visually demonstrates the OER activity of the FeCoP/NF electrode. In situ Raman spectroscopy reveals dynamic surface reconstruction during OER, where FeCoP transforms into active (oxy)hydroxide species (e.g., CoOOH/FeOOH) and high-valent metal-oxo intermediates (Co(IV)–O/Fe(IV)–O), elucidating the origin of its high activity. This work highlights the critical role of phosphide-derived in situ reconstruction in designing high-performance OER electrocatalysts.