Hierarchical MoS2/Ni3S2 core-shell nanofibers for highly efficient and stable overall-water-splitting in alkaline media

Abstract

Non-noble metal electrocatalysts replacing Pt catalyst for efficient hydrogen-evolution reaction (HER) are highly desired to achieve sustainable production of H2 through water splitting. In this paper, we report a novel ammonium intercalated MoS2/Ni3S2 core-shell nanofibers on graphene-Ni foam by a facile method. Such hierarchical nanostructures provide abundant active sites for hydrogen evolution. Furthermore, DFT calculation demonstrates that the intercalated ammonium ions improve the chemisorption of protons for MoS2, thus further enhancing HER activity. The synthesized MoS2/Ni3S2 nanofiber cathode exhibits an overpotential of 109 mV at 10 mA cm−2 in 1 M KOH electrolyte – the lowest overpotential reported so far among any earth-abundant cathodes working in strong alkaline condition. Combining with a nickel iron layered double hydroxide anode, stable overall water splitting with a low potential of 1.59 V at 10 mA cm−2 is achieved in 1 M KOH for 100 h.