Integrating Amorphous Molybdenum Sulfide Nanosheets with a Co₉S₈@Ni₃S₂Array 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 Ni₃S₂nanorods decorated with both Co₉S₈and amorphous MoS_xnanosheets and Ni₃S₂nanowires decorated with amorphous MoS_xnanosheets, namely, MoS_x@Co₉S₈@Ni₃S₂/NF. The synergistic effects from the strong interactions of the heterointerface and unique hierarchical heterostructure endow the MoS_x@Co₉S₈@Ni₃S₂/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^-2for HER and a low overpotential of 310 mV to achieve 100 mA cm^-2for OER. Based on the superior catalytic activity of MoS_x@Co₉S₈@Ni₃S₂/NF for OER and HER, we demonstrated the activity of overall water splitting using MoS_x@Co₉S₈@Ni₃S₂/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^-2than commercial Pt/C/NF||IrO₂/NF (1.61 V) and superior stability. This work provides a platform for the design and preparation of efficient electrocatalysts with various hierarchical heterostructures.