Effect of reaction temperature and reaction time on the structure and properties of MoS₂ synthesized by hydrothermal method

Abstract

In this study, molybdenum disulfide (MoS2) nanostructures were synthesized by a facile hydrothermal process, using ammonium heptamolybdate tetrahydrate ((NH4)6Mo7O24.4H2O) and thiourea (CH4N2S) as the reactants. The effects of experimental parameters including reaction temperatures and reaction times on the structure and morphology of MoS2 have primarily been investigated. The morphology, microstructure, chemical composition and optical properties of as‐synthesized MoS2 were characterized using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), energy dispersive X‐ray spectroscopy (EDS), X‐ray diffraction (XRD), Raman and Photoluminescence spectroscopy. The FESEM and TEM results indicate that depending on the reaction temperature, the three types of morphologies of MoS2 crystals could be obtained. Morphologies of MoS2 changed gradually from aggregated particles to flake‐like structure, then finally to nanosheet morphology with increasing reaction temperature from 160 to 220 oC. However, it was found that the reaction time contributed significantly to the restacking and refinement of MoS2 crystal structure, rather than affecting the morphology of the investigated samples. Both XRD and Raman investigations reveal that the as‐synthesized MoS2 has a hexagonal phase structure (2H‐MoS2). Interestingly, the as‐prepared MoS2 nanosheets exhibit photoluminescence in the visible range with the emitted photon energy of ~1.81 and ~1.95 eV, these properties make MoS2 a promising candidate as the material of choice for next‐generation optoelectronic and photonic devices.

Rare Earth-Doped MoS2 for Supercapacitor Application

“…The diffraction peaks are observed at 14.26, 32.66, 35.84, 39.51, 44.36, 49.87, and 58.07° for the corresponding hkl planes of <002>, <100>, <102>, <103>, <006>, <105>, and <110>, which are similar to the standard JCPDS card number 37–1492 with a hexagonal crystal system. Since the dopant effect is minimum, there is no obvious shift in the peaks and additional peaks observed except for the intensity variation …”

“…Since the dopant effect is minimum, there is no obvious shift in the peaks and additional peaks observed except for the intensity variation. 24 Raman spectroscopy is a potential technique used to identify the structural fingerprint (characteristic vibrational, rotational, and other low-frequency modes) and the influences of doping on the perturbation of the crystal lattice for pure-MoS 2 , Nd-, and Gd-doped MoS 2 samples. There are six vibrational modes observed at 174.44, 275.59, 367.44, 404.25, 822.61, and 988.09 cm −1 (Figure 1b).…”

Engineering the Interface of Cu/MoS2 Nanostructures for Improved Charge Transfer for Applications as PEC Anode Materials

“…The two emission peaks at 670 (A) and 640 nm (B) correspond to the direct transition of A and B excitons, corresponding to A and B processes in Figure c,d i , respectively. The A peak is the direct transition of A excitons between the K point of VB top and the K point of CB bottom, whereas the B peak is the direct transition between CB and lower VB; the energy difference between peaks A and B is attributed to the VB splitting due to the strong spin-orbital interaction. , The accompanying emission peaks at 745 and 780 nm correspond to the first-order and second-order phonon companion lines, respectively. Additionally, the I peak at 810 nm (Figure b) originates from the indirect band gap transition between Γ and K points and appears at a lower wavelength of PL image.…”

MoS2–Nanosheets-Based Catalysts for Photocatalytic CO2 Reduction: A Review

“…Xuan et al found that the reaction time significantly contributes to the restacking of the MoS 2 crystal structure. 145 The significant advantages of these methods are that they use a cheap and abundant sulfur source and produce material of high crystallinity and larger surface area. However, control of the directional growth of MoS 2 layers is difficult in the hydrothermal method; also, the structure is prone to aggregation, and therefore the utilization of surfactants like cetyltrimethylammonium bromide (CTAB) to control the particle shapes 146 is necessary.…”

“…The variation in temperature, pressure, and microwave power (in some cases) can control the morphology, conductivity, microstructure, and composition of the synthesized MoS 2 , which controls the final nature of the as-synthesized MoS 2 . Xuan et al found that the reaction time significantly contributes to the restacking of the MoS 2 crystal structure . The significant advantages of these methods are that they use a cheap and abundant sulfur source and produce material of high crystallinity and larger surface area.…”