2D NiFe ₂ O ₄ /Ni(OH) ₂ Heterostructure‐Based Self‐Supporting Electrode With Synergistic Surface/Interfacial Engineering for Efficient Water Electrooxidation

Abstract To meet the industrial demand for overall water splitting, oxygen evolution reaction (OER) electrocatalysts with low‐cost, highly effective, and durable properties are urgently required. Herein, a facile confined strategy is utilized to construct 2D NiFe ₂ O ₄ /Ni(OH) ₂ heterostructures‐based self‐supporting electrode with surface‐interfacial coengineering, in which abundant and ultrastable interfaces are developed. Under the high molar ratio of Ni/Fe, both spinel oxide and hydroxides phases are formed simultaneously to obtain 2D NiFe ₂ O ₄ /Ni(OH) ₂ heterostructure. The in‐depth analysis indicates that the NiFe ₂ O ₄ /Ni(OH) ₂ interface displays strong electronic interactions and triggers the formation of crystalline‐amorphous coexisting catalytic active NiOOH. Meanwhile, the stable catalyst‐collector interface favors the electron transfer and oxygen molecules transport. The resultant 2D NiFe ₂ O ₄ /Ni(OH) ₂ @CP electrode exhibits superior OER performance, including a low overpotential of 389 mV and a long operating time of 12 h at 1 A cm ⁻² . This work paves a novel method for fabricating efficient and low‐cost electrocatalysts for electrochemical conversation devices.