Design and Epitaxial Growth of MoSe2-NiSe Vertical Heteronanostructures with Electronic Modulation for Enhanced Hydrogen Evolution Reaction

Transition metal dichalcogenides (MX2, where M = Mo or W and X = S or Se) have been regarded as some of the best alternatives for noble metal-free electrocatalysts for the hydrogen evolution reaction (HER). A tremendous number of attempts have mainly focused on the maximization of the number of active edge sites and the conductivity of MX2-based electrocatalysts to enhance HER performance. However, for MX2-based electrocatalysts, the acceleration of the kinetic process to improve HER performance has been neglected until now. Here we report a colloidal epitaxial growth strategy for synthesizing MoSe2-NiSe nanohybrids with well-defined heterointerfaces that are constructed by in situ growth of metallic NiSe nanocrystallites on the MoSe2 nanosheets. These high-quality vertical heteronanostructures with band alignment give rise to the electrons being transferred from the metallic NiSe nanocrystallites to the MoSe2 matrix, achieving the electronic modulation of the MoSe2-NiSe nanohybrids for efficient electrocatalytic activity. The MoSe2-NiSe nanohybrids exhibit excellent HER catalytic properties with a low onset potential of -150 mV, a large cathodic current density (10 mA cm(-2) at an overpotential of 210 mV), and a small Tafel slope of 56 mV per decade. The greatly enhanced electrocatalytic properties were attributed to the electronic structure modulation from the synergetic interactions between NiSe nanocrystallites and MoSe2 nanosheets. We anticipate that the construction of hybrid structures will be a powerful tool for creating high-performance electrocatalysts in solids.