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 MoS2 with a nanosheet structure were investigated in detail. In the presence of glucose, the hydrothermal reaction of sodium molybdate and thiourea yields carbon-loaded MoS2 nanocomposites (C/MoS2). Compared with bare MoS2 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/MoS2 consists of one- or three-layered MoS2 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 MoS2 and carbon spheres of C/MoS2 have a negative charge on the surface, suggesting that the previously reported explanation, in which the adsorption of MoS2 and/or molybdate ions on carbon spheres inhibits the growth and aggregation of MoS2, is not correct. Based on Fourier transform infrared and 1H NMR spectra, it is demonstrated that glucose acts as the hydrogen bond donor toward polyoxomolybdate species such as Mo8O264–, Mo7O246–, and MoO42– in the range of pH = 2–12. The intermolecular hydrogen bond not only inhibits the growth of both the (002) plane of MoS2 and carbon spheres, but also enables the formation of C–O–Mo bonds in the in situ generated C/MoS2. Compared with bare MoS2, C/MoS2 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.