Epitaxial growth of Ni(OH)₂ nanoclusters on MoS₂ nanosheets for enhanced alkaline hydrogen evolution reaction

Constructing heterostructures is an effective strategy for designing efficient electrocatalysts. MoS₂ is a star catalyst for hydrogen evolution reaction (HER) in acidic media; however, the alkaline HER activity is deficient due to the sluggish water dissociation process. Herein, Ni(OH)₂/MoS₂ heterostructures with Ni(OH)₂ nanoclusters epitaxially decorated on the surface of MoS₂ are synthesized towards the alkaline HER. As compared with MoS₂, the epitaxial Ni(OH)₂/MoS₂ heterostructures show significantly enhanced HER activity in 1 M KOH, and the overpotential is decreased by nearly 150 mV to reach a current density of 10 mA cm^-2. The substantial increase in turnover frequency (TOF) demonstrates that the intrinsic activity is greatly improved after the incorporation of Ni(OH)₂ nanoclusters. The presence of Ni(OH)₂ nanoclusters would provide additional water dissociation sites while MoS₂ is ready for the adsorption and combination of the generated H∗, and this so-called synergistic effect eventually induces significantly enhanced alkaline HER kinetics. Besides, the electron transfer from Ni(OH)₂ to MoS₂ increases the proton affinity of MoS₂. The present results describe an interesting case of an atomic-scale electrochemically inert material promoted HER process, and would open a new avenue into designing efficient hetero-nanostructures towards electrocatalytic applications.