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NiFe layered double hydroxide (LDH) based materials arouses great attention because of their outstanding catalytic activity for oxygen evolution reaction (OER) under alkaline condition. However, its catalytic activity for hydrogen evolution reaction (HER) under alkaline condition is relatively poor. Herein, in order to improve the HER catalytic activity of NiFe LDH under alkaline condition, we design a heterostructure of NiS and NiS2 on NiFe LDH, and successfully achieve Mo element doping. The catalyst named NiFe-LDH@Mo-NiS-NiS2/NF possesses a three-dimensional nano-flower-like structure and shows an outstanding catalytic performance for both HER and OER. Specifically, in 1 M KOH solution, it requires the low overpotentials of 261 and 120 mV to achieve the current density of 50 and 10 mA cm-2 for OER and HER, respectively. Simultaneously, when NiFe-LDH@Mo-NiS2-NiS/NF is used as the bifunctional catalysts, it only needs a low voltage of 1.63 V to achieve a current density of 10 mA cm-2. The outstanding catalytic performance is attributed to its special heterostructure and the synergy between Mo and NiSx, resulting in comparability with most reported non-noble metal-based catalysts. The doping of metal elements and the construction of heterostructures provide new ideas for the structure regulation and performance improvement of bifunctional electrocatalysts.

Effective bifunctional catalysts are desirable to replace precious metal materials to promote the development of electrochemical water splitting. Facing with challenge, it is important to design and construct bifunctional electrocatalysts. Herein, we present a highly efficient multifunctional electrocatalyst, i.e., metal-organic framework derived Co3O4@Mo-Co3S4-Ni3S2/NF. (NF: nickle foam). Nano-flowers supported by the nanorods directly grown on the conductive substrate are achieved by doping non-3d high-valence metal Mo during the sulfurization process of ZIF-67 precursor. As a result, the obtained Co3O4@Mo-Co3S4-Ni3S2/NF heterostructure shows outstanding electrochemical performance. Specifically, the low overpotentials of 295 mV and 116 mV are obtained at the current densities of 50 mA cm−2 and 10 mA cm−2 for OER and HER in an alkaline solution, respectively. Moreover, Co3O4@Mo-Co3S4-Ni3S2/NF exhibited excellent catalytic activity with a current density of 10 mA cm−2 at a low voltage of 1.62 V for overall water splitting. This study may provide new methods for metal doping and rationally constructing heterostructure to improve electrochemical performance of catalysts, and is expected to help accelerate progress towards the non-precious metal electrocatalysts for overall water splitting.