DFT-aided experimental investigation on the electrochemical performance of hetero-interface-functionalized CuO nanoparticle-decorated MoS2 nanoflowers for energy storage applications

The present study employed a simple hydrothermal approach to synthesize CuO nanoparticle-decorated MoS2 nanoflowers (MoS2/CuO). The effect of the concentration of CuO(0, 1, 2 wt%, 4, and 6 wt%) on the surface morphological, structural, optical, and electrochemical properties of the composite nanomaterials was studied. Surface imaging reveals the 3D nanoflower morphology of MoS2 and MoS2/CuO nanocomposites. The structural analysis showed a change in the structural parameters due to the incorporation of CuO. Due to the incorporation of CuO, it was determined that the optical band gap of nanocomposites dropped from 1.43 eV to 1.08 eV. The electrochemical performance of the composites was found to be significantly improved due to the decoration of CuO, and the composition with 4 wt% CuO showed the best electrochemical performance possessing a specific capacitance of 336 F g−1 together with 90% capacitive retention after 6000 charge/discharge cycles. The electrochemical performance of the nanocomposite is enhanced by several factors, such as a large surface area, improved structural stability, and minimal charge transfer resistance. Density functional theory was used to theoretically understand the influence of CuO nanoparticles on the electronic and optical properties, as well as the electrochemical performance of the nanocomposite. Theoretical calculations showed that CuO prevents the restacking of MoS2 layers, increasing its active surface area. Hybridization in the interface region between Mo and O orbitals increases states near the Fermi level, leading to higher conductivity, specific capacitance, and a lower optical band gap. The charge transfer from MoS2 to CuO creates a strong intrinsic electric field that improves electron transfer, resulting in longer charging and discharging times and enhanced electrochemical performance.