MoS2 nanosheets grown on nickel chalcogenides: controllable synthesis and electrocatalytic origins for the hydrogen evolution reaction in alkaline solution

Ni-based heterostructures have been regarded as promising catalysts for the hydrogen evolution reaction (HER) in alkaline solutions due to its high efficiency in catalyzing the water dissociation process. Therefore, an in-depth understanding of the water-dissociation-related activity of Ni species within varied structures and coordination environments is significant for the design of novel catalysts. Herein, we synthesized three types of Ni-based heterostructures, namely NiS/MoS2, NiSe/MoS2 and NiSe2/MoS2 by a controllable route to investigate their catalytic trends and origins of the HER under alkaline conditions. Combined with experimental data and theoretical calculation results, we revealed that the alkaline HER activity of the heterostructures relies on the catalyzing ability of Ni species in the Volmer step, which is associated with the d-band center, and is further related to the coordination condition of the Ni atoms in the chalcogenides. With the highest valence state and d-band center among the samples, Ni atoms in NiS exhibit the fastest reaction rate in the Volmer step, thus providing the best catalytic activity for the NiS/MoS2 heterostructure in the alkaline HER. Furthermore, an activity trend for the Ni chalcogenides in the Volmer step, in the order of NiS > NiSe2 > NiSe, has been proposed, which is expected to contribute insights into the design of novel heterostructured catalysts.