Accelerated Oxygen Evolution Kinetics by Engineering Heterojunction Coupling of Amorphous NiFe Hydr(oxy)oxide Nanosheet Arrays on Self‐Supporting Ni‐MOFs

Abstract Designing definite transition metal heterointerfaces is considered an effective strategy for the construction of efficient and robust oxygen evolution reaction (OER) electrocatalysts, but rather challenging. Herein, amorphous NiFe hydr(oxy)oxide nanosheet arrays (A‐NiFe HNSAs) are grown in situ on the surface of a self‐supporting Ni metal–organic frameworks (SNMs) electrode via a combination strategy of ion exchange and hydrolytic co‐deposition for efficient and stable large‐current‐density water oxidation. The existence of the abundant metal–oxygen bonds on the heterointerfaces can not only be of great significance to alter the electronic structure and accelerate the reaction kinetics, but also enable the redistribution of Ni/Fe charge density to effectively control the adsorption behavior of important intermediates with a close to the optimal d‐band center, dramatically narrowing the energy barriers of the OER rate‐limiting steps. By optimizing the electrode structure, the A‐NiFe HNSAs/SNMs‐NF exhibits outstanding OER performance with small overpotentials of 223 and 251 mV at 100 and 500 mA cm⁻², a low Tafel slope of 36.3 mV dec⁻¹, and excellent durability during 120 h at 10 mA cm⁻². This work significantly provides an avenue to understand and realize rationally designed heterointerface structures toward effective oxygen evolution in water‐splitting applications.