Integrating Amorphous Molybdenum Sulfide Nanosheets with a CoS@NiS Array as an Efficient Electrocatalyst for Overall Water Splitting.

It is highly challenging to design low-cost, efficient electrocatalysts for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, a hierarchical heterostructure was constructed on three-dimensional (3D) Ni foam, which contains NiS nanorods decorated with both CoS and amorphous MoS nanosheets and NiS nanowires decorated with amorphous MoS nanosheets, namely, MoS@CoS@NiS/NF. The synergistic effects from the strong interactions of the heterointerface and unique hierarchical heterostructure endow the MoS@CoS@NiS/NF with abundant active sites and effective mass and electron transport pathways, resulting in excellent activity toward both HER and OER in 1 M KOH. It only gives a low overpotential of 76.5 mV to achieve 10 mA cm for HER and a low overpotential of 310 mV to achieve 100 mA cm for OER. Based on the superior catalytic activity of MoS@CoS@NiS/NF for OER and HER, we demonstrated the activity of overall water splitting using MoS@CoS@NiS/NF as both the anode and cathode. It shows a higher catalytic activity for overall water splitting with a low cell voltage of 1.52 V at 10 mA cm than commercial Pt/C/NF||IrO/NF (1.61 V) and superior stability. This work provides a platform for the design and preparation of efficient electrocatalysts with various hierarchical heterostructures.