Size-controlled MoS₂ nanodots supported on reduced graphene oxide for hydrogen evolution reaction and sodium-ion batteries

Transition metal dichalcogenide nanodots (NDs) have received considerable interest. We report a facile bottom-up synthetic route for MoS₂ NDs by using molybdenum pentachloride and L-cysteine as precursors in oleylamine. The synthesis of NDs with a narrow size distribution ranging from 2.2 to 5.3 nm, was tailored by controlling the reaction time. Because of its coating characteristics, oleyalmine leads to uniformity and monodispersity of the NDs. Moreover, the NDs synthesized have large specific surface areas providing active sites. Graphene possesses outstanding conductivity. Combining the advantages of the two materials, the 0D/2D material exhibits superior electrochemical performance because of the 2D permeable channels for ion adsorption, energy storage, and conversion. The as-prepared MoS₂/rGO (~2.2 nm) showed a stable capacity of 220 mAh·g^-1 after 10,000 cycles at the current density of 20 A·g^-1. Furthermore, a reversible capacity ~140 mAh·g^-1 was obtained at a much higher current density of 40 A·g^-1. Additionally, this composite exhibited superior catalytic performance evidenced by a small overpotential (222 mV) to afford 10 mA·cm^-2, and a small Tafel slope (59.8 mV·decade^-1) with good acid-stability. The facile approach may pave the way for the preparation of NDs with these nanostructures for numerous applications.