Strain Effects and Crystalline‐Amorphous Interface of NiFe‐LDH@S‐NiFeO x /NF with Heterogeneous Structure for Enhancing Electrocatalytic Oxygen Evolution Reaction of Water‐Electrolysis

Abstract Electrochemical water‐electrolysis for hydrogen generation often requires more energy due to the sluggish oxygen evolution reaction (OER). This work introduces a double‐layered nanoflower catalyst, NiFe‐LDH@S‐NiFeO x /NF, featuring a crystalline NiFe‐LDH coating on amorphous S‐NiFeO x on nickel foam. Strategically integrating a crystalline‐amorphous (c‐a) heterostructure leverages strain engineering to enhance OER activity with low overpotentials ( η 100 = 220 and η 500 = 245 mV) and stability (135 h at η 100 and 80 h at η 500 ). Theoretical density functional theory (DFT) calculations reveal that the compressive strain can optimize the adsorption of oxygen‐containing intermediates to reduce the reaction energy barrier, thus improving the reaction kinetics and performance of OER. Moreover, its phosphated derivative, NiFeP@S‐NiFeO x /NF, exhibits high hydrogen evolution reaction (HER) performance ( η 10 = 64 mV, η 100 = 187 mV). An alkaline water‐electrolysis cell of NiFeP@S‐NiFeO x /NF(−)||NiFe‐LDH@S‐NiFeO x /NF(+) requires only a cell voltage of 1.77 V at 100 mA cm −2 , demonstrating excellent stability over 110 h (at both 10 and 100 mA cm −2 ). This work highlights the benefits of integrating crystal‐amorphous interfaces and strain effects, offering insights into the understanding and optimizing catalytic OER mechanism and advancing water‐electrolysis technology.