Enhanced electrocatalytic hydrogen evolution by molybdenum disulfide nanodots anchored on MXene under alkaline...

Efficient hydrogen production through electrocatalysis represents a promising path for the future clean energy. Molybdenum disulfide (MoS₂) is a good substitute for platinum-based catalysts, due to its low cost and high activity. However, the limited active sites and low electrical conductivity of MoS₂ hinder its large-scale industrial application under alkaline conditions. Herein, we constructed MoS₂ nanodots anchored on an MXene/nickel foam (MoS₂ NDs/MXene/NF) heterostructure by a cascade polymerization synthesis and in situ vulcanization. The prepared heterostructure displays an ultralow overpotential of 94 mV at a current density of 10 mA cm^-2 with a Tafel slope of only 59 mV dec^-1 in alkaline (1 M KOH) hydrogen evolution reaction (HER), and is better than conventional MoS₂ electrocatalysts reported so far. Fine structural analysis indicates that MoS₂ NDs are dispersed uniformly on the surface of the heterostructure with consistent orientation, leading to the improvement of MoS₂ conductivity with more paths for electron transfer. Moreover, the orientation of the synthesized MoS₂ NDs was verified to expose the more (002) crystal plane, which exhibits higher activity than other planes. Our results demonstrate that MoS₂ NDs with heterostructure design and preferential growth can serve as high-efficiency noble-metal free electrocatalysts for the HER in alkaline solution.