Silver Nanoparticles Embedded on Reduced Graphene Oxide@Copper Oxide Nanocomposite for High Performance Supercapacitor Applications

In this work, silver (Ag) decorated reduced graphene oxide (rGO) coated with ultrafine CuO nanosheets (Ag-rGO@CuO) was prepared by the combination of a microwave-assisted hydrothermal route and a chemical methodology. The prepared Ag-rGO@CuO was characterized for its morphological features by field emission scanning electron microscopy and transmission electron microscopy while the structural characterization was performed by X-ray diffraction and Raman spectroscopy. Energy-dispersive X-ray analysis was undertaken to confirm the elemental composition. The electrochemical performance of prepared samples was studied by cyclic voltammetry and galvanostatic charge-discharge in a 2M KOH electrolyte solution. The CuO nanosheets provided excellent electrical conductivity and the rGO sheets provided a large surface area with good mesoporosity that increases electron and ion mobility during the redox process. Furthermore, the highly conductive Ag nanoparticles upon the rGO@CuO surface further enhanced electrochemical performance by providing extra channels for charge conduction. The ternary Ag-rGO@CuO nanocomposite shows a very high specific capacitance of 612.5 to 210 Fg−1 compared against rGO@CuO which has a specific capacitance of 375 to 87.5 Fg−1 and the CuO nanosheets with a specific capacitance of 113.75 to 87.5 Fg−1 at current densities 0.5 and 7 Ag−1, respectively.

Synthesis of CuO nanosheets via hydrothermal method

In this paper, CuO nanosheets were successfully synthesized by a simple hydrothermal method. The synthesized CuO nanosheets were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier Transform Infrared (FTIR), surface area analysis (BET). Several factors influencing the synthesis of material such as concentration of NaOH, hydrothermal temperature and hydrothermal time were studied. Scanning electron microscopy (SEM) investigation reveals that CuO nanosheets have the length of about 500 - 1000 nm. N2 adsorption–desorption isotherm experiment shows that the BET specific surface area of obtained CuO nanosheets is 12.78 m2/g.

Ultrathin Leaf-Shaped CuO Nanosheets Based Sensor Device for Enhanced Hydrogen Sulfide Gas Sensing Application

Herein, a simple, economical and low temperature synthesis of leaf-shaped CuO nanosheets is reported. As-synthesized CuO was examined through different techniques including field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD), fourier transform infrared spectroscopic (FTIR) and Raman spectroscopy to ascertain the purity, crystal phase, morphology, vibrational, optical and diffraction features. FESEM and TEM images revealed a thin leaf-like morphology for CuO nanosheets. An interplanar distance of ~0.25 nm corresponding to the (110) diffraction plane of the monoclinic phase of the CuO was revealed from the HRTEM images XRD analysis indicated a monoclinic tenorite crystalline phase of the synthesized CuO nanosheets. The average crystallite size for leaf-shaped CuO nanosheets was found to be 14.28 nm. Furthermore, a chemo-resistive-type gas sensor based on leaf-shaped CuO nanosheets was fabricated to effectively and selectively detect H2S gas. The fabricated sensor showed maximum gas response at an optimized temperature of 300 °C towards 200 ppm H2S gas. The corresponding response and recovery times were 97 s and 100 s, respectively. The leaf-shaped CuO nanosheets-based gas sensor also exhibited excellent selectivity towards H2S gas as compared to other analyte gases including NH3, CH3OH, CH3CH2OH, CO and H2. Finally, we have proposed a gas sensing mechanism based upon the formation of chemo-resistive CuO nanosheets.