Multidimensional Ni-Co-sulfide heterojunction electrocatalyst for highly efficient overall water splitting

Heterostructure engineering holds exceptional promise for the development of high-performance electrocatalysts for overall water splitting. However, production of inexpensive and high-efficiency bifunctional electrocatalysts remains a challenge. Herein, we demonstrate a simple method to synthesize a paper-mulberry ( Broussonetia papyrifera )-in-spired Co 9 S 8 @CoNi 2 S 4 /nickel foam (Co 9 S 8 @CoNi 2 S 4 /NF) heterojunction with high catalytic activity and stability. The process involves in situ growth of NiCo layered double hydroxide and in situ derivatization of ZIF-67, followed by the S heteroatom doping. The Co 9 S 8 @CoNi 2 S 4 /NF benefits from the heterostructure and functional advantages of multidimensional building blocks including one-dimensional (1D) nanowires, 2D nanosheets and nanoparticles. The optimized Co 9 S 8 @CoNi 2 S 4 /NF heterojunction with 10% sulphur content reveals excellent electrocatalytic activity with the lower over-potentials of 68 mV for hydrogen evolution reaction (HER) and 170 mV for oxygen evolution reaction (OER) at 10 mA cm −2 in the 1.0 mol L − 1 KOH solution, which is superior to the recently reported transition metal based electrocatalysts. The outstanding performance is attributed to the strong interface coupling between CoNi 2 S 4 and Co 9 S 8 , the advantage of multidimensional structure and the customized electronic structure. The density functional theory suggests that the interface between Co 9 S 8 and CoNi 2 S 4 optimizes the adsorption of the multiple intermediates and further facilitates water splitting kinetics. This work offers a generic approach for heterostructure engineering design of high-performance catalytic system applications.