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

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 (η₁₀₀ = 220 and η₅₀₀ = 245 mV) and stability (135 h at η₁₀₀ and 80 h at η₅₀₀). 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 (η₁₀ = 64 mV, η₁₀₀ = 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.