In Situ Synthesis of High‐Entropy (Oxy)Hydroxides Via Electrochemical Reconfiguration As Catalysts For Efficient Water Oxidation

Abstract Surface reconstruction plays a pivotal role in enhancing the activity of the oxygen evolution reaction (OER), particularly in terms of the structural transformation from metal oxides to (oxy)hydroxides. Herein, a novel (oxy)hydroxide (FeCoNiCuMoOOH) with high entropy is developed by the electrochemical reconstitution of corresponding oxide (FeCoNiCuMoO_x). Significantly, the FeCoNiCuMoOOH exhibits much higher OER electrocatalytic activity and durability with an overpotential as low as 201 mV at a current density of 10 mA cm⁻², and with a Tafel slope of 39.4 mV dec⁻¹. The FeCoNiCuMoOOH/NF presents high stability when testing under a constant current at 100 mA cm⁻² within 1000 h. The surface reconstruction is a process of dissolution‐reprecipitation of Cu and Mo species and co‐hydroxylation of five metal species, which ultimately leads to the formation of FeCoNiCuMoOOH from FeCoNiCuMoOx. This study holds great significance in the realm of designing high‐entropy (oxy)hydroxides catalysts with exceptional activity and stability for OER.