Hierarchical NiFe-LDH on Conductive Ni₃Se₂ Scaffolds for Efficient Oxygen Evolution Reaction

Developing earth-abundant oxygen-evolution reaction (OER) electrodes that operate efficiently at practical current densities remains a challenge because NiFe layered double hydroxides (LDHs), which are among the most active non-noble catalysts in alkaline media, are limited by poor electronic conductivity, nanosheet restacking, and weak contact with current collectors. Herein, we develop a binder-free, integrated NiFe-LDH/Ni₃Se₂@nickel foam (NF) electrode fabricated using a sequential hydrothermal route: Ni₃Se₂ is first grown on NF using Se powder and hydrazine, followed by the in-situ deposition of NiFe-LDH nanosheets. X-ray diffraction verifies the crystalline Ni₃Se₂ backbone and, after LDH growth, a diagnostic low-angle peak near 2θ ≈ 11o is observed, assigned to the (003) basal reflection of hydrotalcite-like LDH. Field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy reveal conformal LDH coverage on the selenide scaffold with uniform Ni, Fe, and O signals, whereas X-ray photoelectron spectroscopy shows mixed-valent Ni²⁺/Ni³⁺ and Fe³⁺ in the shell, preserved Se²⁻ from the core, and hydroxyl/water species in O 1s, consistent with a hydrotalcite-like surface that readily evolves to Ni(Fe)OOH under an anodic bias. Electrochemically, the heterostructure exhibits lower overpotentials at 50–100 mA·cm⁻², a smaller Tafel slope, and reduced charge-transfer resistance relative to NiFe-LDH@NF and Ni₃Se₂@NF. The gains correlate with the largest double-layer capacitance and electrochemically active surface area, and the electrode exhibits stable chronopotentiometric operation. We attribute this performance to synergistic interfacial coupling and rapid electron-transport through Ni₃Se₂, together with abundant, well-wired LDH active sites and improved mass transport in the open 3D foam. This study provides a general strategy for fabricating high-rate alkaline OER electrodes based on LDH/metal selenide heterostructure.