Hydrogen Bond between Molybdate and Glucose for the Formation of Carbon-Loaded MoS2 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.