Strain Effects and Crystalline-Amorphous Interface of NiFe-LDH@S-NiFeO/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/NF, featuring a crystalline NiFe-LDH coating on amorphous S-NiFeO on nickel foam. Strategically integrating a crystalline-amorphous (c-a) heterostructure leverages strain engineering to enhance OER activity with low overpotentials (η = 220 and η = 245 mV) and stability (135 h at η and 80 h at η). 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/NF, exhibits high hydrogen evolution reaction (HER) performance (η = 64 mV, η = 187 mV). An alkaline water-electrolysis cell of NiFeP@S-NiFeO/NF(-)||NiFe-LDH@S-NiFeO/NF(+) requires only a cell voltage of 1.77 V at 100 mA cm, demonstrating excellent stability over 110 h (at both 10 and 100 mA cm). 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.