Dominating Role of Aligned MoS 2 /Ni 3 S 2 Nanoarrays Supported on Three-Dimensional Ni Foam with Hydrophilic Interface for Highly Enhanced Hydrogen Evolution Reaction.

When using water splitting to achieve sustainable hydrogen production, low-cost, stable, and naturally abundant electrocatalysts are required to replace Pt-based ones for the hydrogen evolution reaction (HER). Herein, for the first time, a novel nanostructure with one-dimensional (1D) MoS ₂ /Ni ₃ S ₂ nanoarrays directly grow on a three-dimensional (3D) Ni foam is developed for this purpose, showing excellent catalytic activity and stability. The as-prepared 3D MoS ₂ /Ni ₃ S ₂ /Ni composite has an onset overpotential as low as 13 mV in 1 M KOH, which is comparable to Pt-based electrocatalyst for HER. According to the classical theory, the Tafel slope of the new composite is relatively low, as it goes through a combined Volmer-Heyrovsky mechanism during hydrogen evolution. All the results attribute the excellent electrocatalytic activity of the nanostructure to the electrical coupling among Ni, Ni ₃ S ₂ , and MoS ₂ , the super hydrophilic interface, the synergistic catalytic effects produced by the MoS ₂ /Ni ₃ S ₂ nanoarrays, and abundant exposed active edge sites. These unique and previously undeveloped characteristics of the 3D MoS ₂ /Ni ₃ S ₂ /Ni composite make it a very promising earth-abundant electrocatalyst for HER.