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Developing efficient oxygen evolution reaction (OER) electrocatalysts with earth-abundant elements is very important for sustainable H 2 generation via electrochemical water splitting. Here we design a crystalline-amorphous Ni–Fe–Al hybrid phosphides nanosheet arrays grown on NiFe foam for efficient OER application. Dynamic surface reorganization of phosphides at anodic/cathodic polarizations is probed by in situ Raman spectroscopy. The reconstructed amorphous Ni(Fe)OOH species are determined as the active phases that facilitate the OER process. This unique electrode shows highly catalytic activity toward water oxidation, achieving the current densities of 10 and 100 mA cm−2 at 181 and 214 mV in 1 M KOH, respectively. Meanwhile, it also exhibits excellent stability at a large current density of 100 mA cm−2 for over 60 h. This work reveals the dynamic structural transformation of pre-catalyst in realistic conditions and highlights the important role of oxyhydroxides as real reactive species in OER process with high activity. [Display omitted] • Ni–Fe–Al hybrid phosphides nanosheet arrays were synthesized for OER. • Dynamic self-reconstruction was revealed by in situ Raman spectroscopy. • Amorphous Ni(Fe)OOH species act as the real active phases. • Regenerated pre-catalyst shows excellent OER activity. [ABSTRACT FROM AUTHOR]