In situ unraveling surface reconstruction of Ni₅P₄@FeP nanosheet array for superior alkaline oxygen evolution reaction

Oxygen evolution reaction (OER) is a key step for electrochemical water splitting and understanding the surface reconstruction of OER pre-catalysts is of vital importance. Herein, hybrid Ni₅P₄ @FeP nanosheet arrays were evaluated as promising OER pre-catalysts. The dynamic surface evolution was probed by in situ Raman spectroscopy, which revealed that Ni₅P₄ @FeP was rapidly reconstructed to NiFe₂O₄ during the anodic scan. The structural instability of amorphous NiFe₂O₄ led to partial reconstitution to Ni/FeOOH at high oxidation potentials. As-formed Ni/FeOOH@NiFe₂O₄ hybrid with high structural reversibility was established as a truly active species, which exhibited excellent alkaline OER performance with a low overpotential of 205 and 242 mV under current densities of 10 and 100 mA cm⁻², respectively. This work provides a facile strategy to in situ construct an amorphous spinel/oxyhydroxide hybrid structure using electrochemical activation that holds strong promise for potential application in electrochemical water splitting and related energy devices.