Abstract:
The incorporation of MnS nanoparticles on the surface morphological, structural, chemical, optical, and electrochemical performance of 2H-MoS2 nanoflower (MoS2/MnS) synthesized by a facile hydrothermal method was studied. The morphological study performed by FESEM and HRTEM showed that the incorporation of MnS nanoparticles distorted the lattice fringe and increased the interlayer spacing of the MoS2 nanoflower. The different structural parameters of the composite nanomaterials were investigated by XRD. The microstrain of the nanocomposites was found to vary with the concentration of MnS nanoparticles. The Raman spectra of MoS2/MnS showed that interfacial interaction occurred between the MoS2 and MnS interfaces causing n-type doping in the nanocomposites due to the incorporation of MnS nanoparticles. The optical study was performed by UV-Vis spectroscopy, which showed a reduction of the optical band gap from 1.68 eV to 1.54 eV due to the incorporation of MnS nanoparticles. The XPS analysis revealed a partial conversion from 2H-MoS2 to 1T-MoS2, together with the formation of defect states in the nanoflower due to the creation of sulfur vacancies by incorporation of MnS nanoparticles. The electrochemical properties of the MoS2/MnS nanocomposites was studied by an electrochemical workstation. For MnS nanoparticles decorated MoS2 nanoflower a highest specific capacitance of 351 Fg-1 at a current density of 0.3 Ag-1. The composite nanomaterials exhibit a capacitive retention of 80% after 8,000 charging and discharging cycles. The density function theory (DFT) revealed formation of defect states in the forbidden energy region due to the strong hybridization between Mo-d and Mn-d orbitals occurred due to the incorporation of MnS. The improved electrochemical performance of MoS2/MnS nanocomposite can be attributed to the defect-rich 1T-MoS2 phase, together with the enlarged surface area and increased interlayer spacing originated from the decoration of MnS nanoparticles. The combined experimental and theoretical approach used in this thesis work will open up an economic and sustainable route for the fabrication of efficient energy storage devices.
