1D/2D core-shell structure Ni-Mo-S@NiFe LDH grown on nickel foam: a bifunctional electrocatalyst for efficient oxygen evolution and urea oxidation reactions.

The construction of bifunctional catalysts for the oxygen evolution reaction (OER) and urea oxidation reaction (UOR) is important for accelerating the development of the hydrogen economy. Herein, a novel three-dimensional core-shell heterostructure (Ni-Mo-S@NiFeLDH/NF) was prepared by vertically growing NiFe layered double hydroxide (NiFe LDH) nanosheets on nickel foam (NF)-supported arrays of Ni-Mo-S (NiS, NiS, MoS) nanorods a hydrothermal-sulfide-hydrothermal process. Benefiting from the unique core-shell structure with numerous exposed active sites, the optimized Ni-Mo-S@NiFe LDH/NF shows excellent OER/UOR activity, with an overpotential of only 274 mV for OER to reach 100 mA cm and 1.318 V for UOR to reach 10 mA cm. Moreover, the assembled Ni-Mo-S@NiFe LDH||Pt/C urea electrolytic system requires only 1.348 V to achieve 10 mA cm, as much as 159 mV lower than pure water electrolysis. This work provides an idea for researching NiFe LDH-based OER/UOR bifunctional catalysts.