Construction of CoS/NiS@CuS with dandelion flower-like heterostructures as efficient catalysts for overall urea splitting

Abstract

The exploration of efficient and inexpensive electrocatalysts is of great importance for sustainable hydrogen production by water splitting. In this paper, we reported a simple preparation method for in situ growth of NiCoOOH@CuO on nickel foam by a two-step hydrothermal method to generate CoS/NiS@CuS with a dandelion-like heterostructure after a one-step sulfidation. The CoS/NiS@CuS electrode has excellent electrochemical properties for urea oxidation reactions, oxygen evolution reactions and urea electrolysis. Electrochemical performance was tested in alkaline solution, the overpotential of CoS/NiS@CuS is only 190 mV for the oxygen evolution reaction, the potential of CoS/NiS@CuS is only 1.35 V for urea oxidation, and the overpotential of CoS/NiS@CuS is only 110 mV at 10 mA cm−2 for the hydrogen evolution reaction, which are one of the best activities reported so far. Density functional theory calculations show that CoS2 exhibits the minimum Gibbs free energy of hydrogen, which plays an important role in promoting the reaction rate. The presence of CoS2 increases the electrical conductivity of the material, and synergistic effect of NiS and CuS makes the material exhibit superior hydrogen production properties. Our work proves that transition-metal sulfides have great potential in the direction of urea splitting, which provides new ideas and directions for subsequent exploration in the direction of transition-metal sulfides.