Enhanced Supercapacitor Performance and Electromagnetic Interference Shielding Effectiveness of CuS Quantum Dots Grown on Reduced Graphene Oxide Sheets

Abstract

This study is focused on the preparation of the CuS/RGO nanocomposite via the hydrothermal method using GO and Cu-DTO complex as precursors. X-ray diffraction, Fourier-transform infrared spectroscopy, and Raman and X-ray photoelectron spectroscopy study revealed the formation of the CuS/RGO nanocomposite with improved crystallinity, defective nanostructure, and the presence of the residual functional group in the RGO sheet. The morphological study displayed the transformation of CuS from nanowire to quantum dots with the incorporation of RGO. The galvanostatic charge/discharge curve showed that the CuS/RGO nanocomposite (12 wt % Cu-DTO complex) has tremendous and outperforming specific capacitance of 3058 F g^-1 at 1 A g^-1 current density with moderate cycling stability (∼60.3% after 1000 cycles at 10 A g^-1). The as-prepared nanocomposite revealed excellent improvement in specific capacitance, cycling stability, Warburg impedance, and interfacial charge transfer resistance compared to neat CuS. The fabricated nanocomposites were also investigated for their bulk DC electrical conductivity and EMI shielding ability. It was observed that the CuS/RGO nanocomposite (9 wt % Cu-DTO) exhibited a total electromagnetic shielding efficiency of 64 dB at 2.3 GHz following absorption as a dominant shielding mechanism. Such a performance is ascribed to the presence of interconnected networks and synergistic effects.

Figure 1

(a) XRD pattern of CuS, RGO, and CuS/RGO nanocomposites and (b) Raman spectra of CuS, RGO, and RGCS12 nanocomposites.

Figure 2

XPS spectra of the RGCS12 nanocomposite: (a) full survey spectrum, (b) C 1s, (c) Cu 2p, and (d) S 2p region.

Figure 3

FESEM images of (a) CuS, (b) RGO, (c) RGCS9, and (d) low-magnified and (e) high-magnified RGCS12 and RGCS17.

Figure 4

HRTEM image of RGCS12: (a) low magnification, (b) high magnification, (c) image with a lattice fringe, and (d) SAED pattern.

Figure 5

Schematic presentation of the formation of CuS nanowires and CuS/RGO nanocomposites.

Figure 6

(a) CV curve of CuS/RGO nanocomposites, RGO and CuS at 5 mV s^–1 and (b) discharge curve of CuS/RGO nanocomposites, RGO and CuS at 1 A g^–1 current density.

Figure 7

(a) Plot of specific capacitance vs scan rate, (b) plot of specific capacitance vs current density, and (c) plot of specific capacitance vs number of cycle for CuS, RGO, and RGCS12. (d) Nyquist plot of CuS, RGO, and RGCS12 over the frequency range of 0.1 Hz to 100 kHz.

Figure 8

Plots of (a) SE_A vs frequency, (b) SE_R vs frequency, and (c) SE_T vs frequency for CuS, RGO, and CuS/RGO nanocomposites and (d) 3-D representation of average EMI SE of CuS, RGO, and CuS/RGO nanocomposites.