Tree-Like NiS2/MoS2-RGO Nanocomposites as pH Universal Electrocatalysts for Hydrogen Evolution Reaction

Abstract The electrocatalytic activity of transition metal dichalcogenides (TMDs) is largely dependent on the exposed massive active sites and electrical conductivity of the catalysts. In this work, a tree-like nanocomposite (NiS 2 /MoS 2 -RGO) which is composed of bimetal sulfide (NiS 2 /MoS 2 ) nanocomposites uniformly anchored on the surface of reduced graphene oxide (RGO) was successfully synthesized. As a catalytic material for the hydrogen evolution reaction (HER), the NiS 2 /MoS 2 -RGO composites exhibit significantly enhanced electrocatalytic activity and impressive long-term stability for the hydrogen evolution reaction over a wide pH range. The tree-like NiS 2 /MoS 2 -RGO nanocomposites afford a current density (η 10 ) of 10 mA/cm 2 at small overpotentials of 172, 144 and 229 mV, and have a small Tafel slope of 51, 82 and 103 mV/dec in acidic, alkaline and neutral solution, respectively. Further studies reveal that the effective activities benefit from the abundant active edge sites and defects of NiS 2 /MoS 2 nanocomposites and the excellent conductivity of RGO. Graphical Abstract