Mo-Doped Co₃S₄/CoSe₂ Nanosheet Heterostructures for Efficient Water Splitting in a Wide pH Range

Heterostructure catalysts are the key to reducing the energy barrier and raising the energy conversion efficiency of the overall water splitting (OWS). In this work, a starfish-like Mo-doped Co 3 S 4 /CoSe 2 heterostructure catalyst on nickel foam (Mo-Co 3 S 4 /CoSe 2 /NF) has been constructed by a facile hydrothermal synthesis. Three-dimensional (3D) nanosheet networked architecture of the catalyst can significantly increase the active surface area and exposed active sites; metal-ion doping can regulate the electronic structure, boost the adsorption of reaction intermediates, and enhance the intrinsic activity; the heterogeneous effect can further improve the catalytic activity; the robust structure of nickel foam can further strengthen the stability. Benefiting from these merits, Mo-Co 3 S 4 /CoSe 2 /NF exhibited an exceptional electrocatalytic performance at wide pH and at large current density. For the hydrogen evolution reaction (HER), the overpotentials at 200 mA cm –2 were 215 and 191 mV in alkaline and acidic media, respectively, as well as 127 mV at 10 mA cm –2 in neutral media. For the oxygen evolution reaction (OER), the overpotential at a large current density of 500 mA cm –2 was only 336 mV in alkaline media. The cell voltage for the OWS was just 1.715 V to achieve 200 mA cm –2 with long-term stability for 100 h in alkaline media. This work suggests that the construction of metal-doped heterostructure catalysts is an effective strategy to enhance the OWS performance.