Hydrogen Bond between Molybdate and Glucose for the Formation of Carbon-Loaded MoS 2 Nanocomposites with High Electrochemical Performance.

The effects of glucose on the growth and surface properties of MoS ₂ with a nanosheet structure were investigated in detail. In the presence of glucose, the hydrothermal reaction of sodium molybdate and thiourea yields carbon-loaded MoS ₂ nanocomposites (C/MoS ₂ ). Compared with bare MoS ₂ nanosheets with more than six layers obtained in the absence of glucose and carbon spheres with a diameter of 500 nm prepared from the carbonization of glucose, C/MoS ₂ consists of one- or three-layered MoS ₂ and carbon spheres with a diameter less than 1 nm to give a large Brunauer-Emmett-Teller surface area (3-20 times larger than the individual materials). The surface characterizations reveal that both MoS ₂ and carbon spheres of C/MoS ₂ have a negative charge on the surface, suggesting that the previously reported explanation, in which the adsorption of MoS ₂ and/or molybdate ions on carbon spheres inhibits the growth and aggregation of MoS ₂ , is not correct. Based on Fourier transform infrared and ¹ H NMR spectra, it is demonstrated that glucose acts as the hydrogen bond donor toward polyoxomolybdate species such as Mo ₈ O ₂₆ ^4- , Mo ₇ O ₂₄ ^6- , and MoO ₄ ^2- in the range of pH = 2-12. The intermolecular hydrogen bond not only inhibits the growth of both the (002) plane of MoS ₂ and carbon spheres, but also enables the formation of C-O-Mo bonds in the in situ generated C/MoS ₂ . Compared with bare MoS ₂ , C/MoS ₂ not only show a lower over-potential by 60 mV for the electrocatalytic evolution of hydrogen, but also has a larger mass specific capacitance by three times, due to the larger surface area and the interfacial interaction through the C-O-Mo bonds.