Integrating Amorphous Molybdenum Sulfide Nanosheets with a Co 9 S 8 @Ni 3 S 2 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 Ni 3 S 2 nanorods decorated with both Co 9 S 8 and amorphous MoS x nanosheets and Ni 3 S 2 nanowires decorated with amorphous MoS x nanosheets, namely, MoS x @Co 9 S 8 @Ni 3 S 2 /NF. The synergistic effects from the strong interactions of the heterointerface and unique hierarchical heterostructure endow the MoS x @Co 9 S 8 @Ni 3 S 2 /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 -2 for HER and a low overpotential of 310 mV to achieve 100 mA cm -2 for OER. Based on the superior catalytic activity of MoS x @Co 9 S 8 @Ni 3 S 2 /NF for OER and HER, we demonstrated the activity of overall water splitting using MoS x @Co 9 S 8 @Ni 3 S 2 /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 -2 than commercial Pt/C/NF||IrO 2 /NF (1.61 V) and superior stability. This work provides a platform for the design and preparation of efficient electrocatalysts with various hierarchical heterostructures.