Core/shell cable-like Ni3S2 nanowires/N-doped graphene-like carbon layers as composite electrocatalyst for overall electrocatalytic water splitting

A new core/shell 1-D nanostructure based on Ni3S2 nanowires and N-doped graphene-like carbon layers on nickel foam (i.e. Ni3S2@NGCLs/NF) has been fabricated and applied as composite electrocatalyst for oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and overall water splitting. The Ni3S2@NGCLs exhibit a unique architecture with a well-defined core–shell cable-like one-dimensional nanostructure in which NGCLs act as conductive shell and Ni3S2 nanowire as active core. The composite has a nitrogen content of 6.39% in atomic ratio. The Ni3S2@NGCLs/NF shows low overpotentials of 271 mV and 134 mV at 10 mA cm−2 in 1.0 M KOH for OER and HER, respectively. Highly durable OER and HER performances were demonstrated by 40 h chronopotentiometry and 10,000 CV cycle tests. Excellent overall water splitting electrocatalytic activity was found in a Ni3S2@NGCLs/NF‖Ni3S2@NGCLs/NF two-electrode system. Particularly, an active-phase NiOOH, a highly active substance for OER, can be controllably formed in the reaction process due to the shell structure of multi-layer carbon that slows down the dissolution of Ni3S2. Theoretical calculations suggest that Ni3S2@NGCLs/NF has a lower ΔG (H*) value of 0.51 eV for HER and lower overpotential value of 0.39 V for OER. These results suggest that the composite structure is a promising bifunctional electrocatalyst.