Design heterostructure of NiS–NiS2 on NiFe layered double hydroxide with Mo doping for efficient overall water splitting

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.