Mo-doping and construction of the heterostructure between NiFe LDH and NiSx co-trigger the activity enhancement for overall water splitting.

To reduce the preparation cost of high-purity hydrogen, it is necessary to search suitable non-precious metal catalysts with high activity and robust stability. Herein, two means (heteroatom-doping and the heterostructure construction) were adopted together to improve the dual-function activity of NiFe LDH which was widely used in water electrolysis. Mo doped NiFe LDH nanoflowers were firstly generated by hydrothermal reaction, and then NiSx was modified on the petals via electrodeposition. Finally, the obtained NF/Mo-NiFe LDH/NiSx with large electrochemical active area exhibits the expected electrochemical performance with the overpotential at 100 mA cm-2 of 169 and 249 mV for hydrogen evolution (HER) and oxygen evolution reaction (OER) respectively. Assembling NF/Mo-NiFe LDH/NiSx into a two-electrode device for the integral water electrolysis, it just requires a cell voltage of 1.69 V to drive a current density of 100 mA cm-2, and keeps stable after 50-hour continuous operation in 1.0 M KOH. Mo-doping not only regulates the electronic structure of the transition metals and reduces the energy barrier of HER intermediates, but also facilitates the generation of reactive sites for OER. Meanwhile, the construction of heterointerface ensures the synergism between NiSx and Mo-NiFe LDH and accelerates the electron transfer across interfaces, thus enhancing the bifunctional performance.