Interface engineering of Ni3S2@NiFe-LDH core-shell heterostructure to achieve energy-saving hydrogen production

Abstract

Developing highly active and cost-effective catalysts for oxygen evolution reaction (OER) and urea oxidation reaction (UOR) is crucial to accelerate the scale-up of hydrogen production. However, their potentials in widespread use have been locked owing to the sluggish reaction kinetics. Herein, we present a unique three-dimensional heterostructure, in which the self-supported Ni₃S₂ nanorods are wrapped by ultrathin nickel-iron layered double hydroxide nanosheets on nickel foam (Ni₃S₂@NiFe-LDH/NF). Benefiting from the uniform core-shell architecture and the modulated electronic structure, Ni₃S₂@NiFe-LDH/NF demonstrates superior activities for both OER and UOR. The electrode manifests an ultralow overpotential of 300 mV is required for OER to attain 100 mA cm^-2 and operates stably for 200 h at 100 mA cm^-2. Impressively, the UOR and overall water-urea electrolysis solely require 1.38 V vs. RHE and 1.43 V to supply 100 mA cm⁻², greatly reducing the overall energy consumption in 1.0 M KOH with a 0.33 M urea. The in-situ Raman characterization results show that Ni₃S₂@NiFe-LDH undergoes surface reconstruction into crystalline γ-Ni(Fe)OOH during OER, while it transforms into amorphous a-Ni(Fe)OOH during UOR. This work demonstrates an effective interfacial engineering strategy to develop Ni-based catalysts, enabling energy-saving H₂ production by efficient OER and UOR.