RGO/MgO hybrid nanocomposites with high specific capacitance (original) (raw)
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Iranian Journal of Materials Science and Engineering, 2020
The graphene oxide -TiO2 (GO-TiO2) and pre-reduced graphene oxide -TiO2 (rGO-TiO2) D ow nl oa de d fr om ij m se .iu st .a c. ir at 3 :0 0 IR D T o n S un da y M ay 1 6t h 20 21 [ D O I: 10 .2 20 68 /ij m se .1 7. 4. 55 ] Z. Abasali karaj abad, A. Nemati, A. Malek Khachatourian and M. Golmohammad 56 56.2 and 18.4F/g at a scan rate of 100mVs, for nanobelts and nanoparticles, respectively [17]. Sun et al. used atomic layer deposition to coat graphene sheets with TiO2 nanoparticles and demonstrated a specific capacitance of 75 Fg at a scan rate of 10 mVs [18]. Liu et al. have also investigated a GO/TiO2 nanorod composite to attain a specific capacitance of 100F/g at 5mVs scan rate [19]. Reduction of GO make changes in its physical and chemical properties [20], so it appears that the pre-reduction of GO will also affect the electrochemical properties of GO/TiO2 nanocomposite. The latter point has not been studied by other researchers to the best of authors’ knowledge. In this research, ...
Ceramics International, 2018
We report a simple and novel synthesis of reduced graphene oxide/silver/cobalt oxide novel nanocomposites (rGO-SCO) as an electrode material for supercapacitor applications by one-step reflux method. The graphene oxide was initially reduced to reduced graphene oxide (r-GO) by simple heat treatment in the presence of reducing agent(NaBH 4). The prepared r-GO was refluxed with the appropriate quantities of cobalt nitrate and silver nitrate for overnight to get high surface area r-GO decorated with silver / cobalt oxide nanocomposite material. In the prepared nanocomposite, r-GO acts as a substrate to hold the oxides which in turn enhance the conductivity of the prepared nanocomposite material. The nanocomposites were subjected to the physical characterization, such as XRD,which reveals the confirmation and formation of the prepared composites with the well crystallinity nature and crystallite size of 3.5nm.FTIR confirms the removal of epoxy groups in reduced graphene oxide and metal-oxygen vibration band in the composite. Surface morphologywas analysed by SEM and HR-TEM, which discloses that the reduced graphene oxideis being retained in the composite and promotes ion diffusion process. EDAX confirms the exact elemental composition in the composite. The electrochemical performance of the prepared rGO-SCO composites was examined by cyclic voltammetry, charge-discharge and A.C. impedance analysis. The maximum specific capacitance obtained on rGO-SCO nanocomposite was 979.52 Fg-1 at a current density of 0.25 Ag-1 along with high cycling stability of 94.05% for 1000 cycles.
Journal of Alloys and Compounds, 2017
In this paper, graphene oxide (GO) was firstly synthesized by modification of Hummers method from the literature. Secondly, reduced graphene oxide (rGO)/Titanium oxide (TiO 2) nanocomposites were synthesized with different wt/wt % of GO/TiO 2 (1:1; 1:2; 1:5 and 1:10) by microwave-assisted method. By treating GO and GO/TiO 2 nanocomposites in a microwave oven, reduced graphene oxide (rGO) and rGO/TiO 2 materials could be obtained within power of 180 W in 10 min. The weight ratio of rGO and TiO 2 was used to obtain the optimum conditions for nanocomposite materials. The rGO/TiO 2 nanocomposite active materials were characterized by cyclic voltammetry (CV), Fourier-transfrom infrared-Attenuated total reflectance (FTIR-ATR), scanning electron microscopy-energy dispersion Xray (SEM-EDX), thermogravimetry (TGA), differential thermal analyzer (DTA) and electrochemical impedance spectroscopy (EIS) analysis. Thirdly, supercapacitors were fabricated as a symmetric device with two electrode configuration. The device performances were tested by CV, galvanostatic constant current (CC), and EIS measurements. TGA analysis indicated that the thermal stability of the nanocomposites improved from rGO (40% at 892.8 0 C) to nanocomposite as the initial feed ratio of [GO] o /[TiO 2 ] o =1/10 as 94% at 949.3 0 C) increased. The result show that the as-prepared symmetrical rGO/TiO 2 nanocomposite on the two-electrode system displays very high specific capacitance of 524.02 F/g at 2 mV/s for [GO] o /[TiO 2 ] o = 1/5 with a high energy density of E= 50.07 Wh/kg at 2 mV/s for [GO] o /[TiO 2 ] o = 1/1 and high power density of P= 58.6 kW/kg at a the scan rate 1000 mV/s for [GO] o /[TiO 2 ] o = 1/1. Additionally, the symmetric electrode shows good cycling stability with a retention value of 6.6% for [GO] o /[TiO 2 ] o = 1/1 after 1000 cycles. These good results suggest us that rGO/TiO 2 nanocomposite which is obtained by microwave-assisted method has a great potential as an electrode material for supercapacitor applications. Research Highlights 1-Synthesis of rGO, rGO/TiO 2 nanocomposites in the initial feed ratio of [GO] o /[TiO 2 ] o = 1/1, ½, 1/5 and 1/10. 2-Supercapacitor device fabrication of rGO, and rGO/TiO 2 nanocomposites in different feed ratios. 3-Energy density, power density and capacitance measurements of rGO, and rGO/TiO 2 nanocomposites.
Mg(OH)2/rGO nanocomposites for high performance electrodes
Materials Today: Proceedings, 2019
Mg(OH)2 nanoparticles and Mg(OH)2-rGO nanocomposites were prepared by microwave assisted co-precipitation method. The morphological study of the as-prepared samples was done by Transmission electron microscopy (TEM). The real and imaginary parts of complex impedance were studied as a function of frequency over a range of 50Hz to 5MHz at room temperature. The Nyquist plots were recorded to know the resistance contribution from grains and grain boundaries. DC conductivity () has been studied as a function of temperature by using two probe method. A minor increase in GO concentration causes increases in the value of in the nanocomposites. The activation energy () was calculated by using Arrhenius equation and its value decreases with the increases in the GO concentration. concentration.
Synthesis of reduced Graphene Oxide (rGO) using different treatments of Graphene Oxide (GO)
IOP Conference Series: Materials Science and Engineering, 2018
In this work, a combined chemical and mechanical method was used for the production of graphene instead of chemical method only. The use of mechanical sonication was to assists exfoliation graphene oxide (GO) besides the used of chemical reagents. Then, the reduction of GO into graphene was carried out using L-ascorbic acid. The effects sonication cause synthesis of GO undergoes peeling graphitic layer and at the same time expose the layer with oxidizing agent. The properties of GO and reduced-graphene oxide (rGO) using various routes were investigated using XRD and FTIR. The main characteristics peak was observed at 7 o and 9 o for GO prepared using sonication and without sonication, respectively. The decreased of 2-theta degree of GO prepared using sonication indicates that the d-value becomes bigger. Estimation of average diameter rGO (with sonication) was 24.49 nm while rGO (without sonication) was 126.2 nm. The reduction of both GO was then carried out using an environmentally reducing agent, ascorbic acid. It was found that the L-ascorbic acid was effective in removing oxygenated functional groups. The conductivity values obtained for rGOs was 7640 S/m while rGO-ws was is 678 S/m.
Nanosystems: Physics, Chemistry, Mathematics
A globally acknowledged green synthesis of reduced graphene oxide (rGO) from graphene oxide (GO) is presented in this paper. The graphene oxide powder was synthesized from Graphite powder by a modification of Hummer's method. The GO is exposed to focused sunlight to obtain reduced graphene oxide (rGO). The reduction of GO under solar light is an eco-friendly method to conventional method of rGO preparation. The mechanism of the reduction of GO by sunlight imperative to exfoliation was seen to be well defined. The rGO powder was characterized by Xray Diffraction (XRD), Field-Emission Scanning Electron Microscopy (FESEM), Raman spectroscopy, Fourier-Transform Infrared Spectroscopy (FTIR) and High-Resolution Transmission Electron Microscopy (HRTEM). This eco-friendly method of synthesizing of rGO paves way for an alternative method of rGO nanosheets preparation and it can be effectively used for fabrication of various electronic devices.
Nanomaterials
Composites of synthesized reduced graphene oxide (rGO) and titanium dioxide nanotubes (TNTs) were examined and combined at different mass proportions (3:1, 1:1, and 1:3) to develop an electrochemical double layer capacitor (EDLC) nanocomposite. Three different combination methods of synthesis—(1) TNT introduction during GO reduction, (2) rGO introduction during TNT formation, and (3) TNT introduction in rGO sheets using a microwave reactor—were used to produce nanocomposites. Among the three methods, method 3 yielded an EDLC nanomaterial with a highly rectangular cyclic voltammogram and steep electrochemical impedance spectroscopy plot. The specific capacitance for method 3 nanocomposites ranged from 47.26–165.22 F/g while that for methods 1 and 2 nanocomposites only ranged from 14.03–73.62 F/g and 41.93–84.36 F/g, respectively. Furthermore, in all combinations used, the 3:1 graphene/titanium dioxide-based samples consistently yielded the highest specific capacitance. The highest am...
This paper reports simultaneous modification of graphene oxide (GO) papers by functionalization with MgCl2. The Mg2+ ions enhance both the interlayer cross-links and lateral bridging between the edges of adjacent GO sheets by forming Mg–O bonds. The improved load transfer between the GO sheets gives rise to a maximum of 200 and 400% increases in Young’s modulus and tensile strength of GO papers. The intercalation of chlorine between the GO layers alters the properties of GO papers in two ways by forming ionic Cl– and covalent C–Cl bonds. The p-doping effect arising from Cl contributes to large enhancements in electrical conductivities of GO papers, with a remarkable 2500-fold surge in the through-thickness direction. The layered structure and the anisotropic electrical conductivities of reduced GO papers naturally create numerous nanocapacitors that lead to charge accumulation based on the Maxwell–Wagner (MW) polarization. The combined effect of much promoted dipolar polarizations due to Mg–O, C–Cl, and Cl– species results in an exceptionally high dielectric constant greater than 60 000 and a dielectric loss of 3 at 1 kHz by doping with 2 mM MgCl2. The excellent mechanical and electrical properties along with unique dielectric performance shown by the modified GO and rGO papers open new avenues for niche applications, such as electromagnetic interference shielding materials.
The Enhanced Energy Density of rGO/TiO2 Based Nanocomposite as Electrode Material for Supercapacitor
Electronics
TiO2 electrode material is a poor choice for supercapacitor electrodes because it has low conductivity, poor cyclic stability, and a low capacitance value. It is inevitable to enhance electrode materials of this kind by increasing the surface area and combining high electronic conductivity materials. In the current research work, it was proposed to combine reduced graphene oxide (rGO) as it might provide a large surface area for intercalation and deintercalation, and also, it could establish the shorter paths to ion transfer, leading to a reduction in ionic resistance. The size, surface morphology, and crystalline structure of as-prepared rGO/TiO2 nanocomposites were studied using HRTEM, FESEM, and XRD, respectively. Using an electrochemical workstation, the capacitive behaviors of the rGO/TiO2 electrode materials were assessed with respect to scan rate and current density. The capacitances obtained through cyclic voltammetry and galvanostatic charge-discharge techniques were found ...
2019
High quality reduced graphene oxide (RGO) nanosheets were prepared from natural graphite using an improved modified Hummers method. The morphological, structural and electrochemical properties of the RGO were characterised by scanning electron microscope (SEM), Raman spectroscopy, X-ray diffraction (XRD) analysis, Cyclic Voltammetry (CV) analysis and Electrochemical Impedance Spectroscopy (EIS) analysis. The SEM image of the RGO showed that, there was a small increase in the number of grain boundaries, indicating a collapse of the surface coalescence of the graphene oxide. The XRD peak at 24.56˚ corresponds to the (002) diffraction plane with the interlayer spacing along the c-axis of 2.0989 Ǻ. The Raman shift for the reduced graphene oxide gives the ID/IG intensity ratio of 1.04. The RGO exhibited good electrochemical characteristics with energy density and power density of 19.2 Whkg -1 and 149.3 Wkg -1 respectively. Keywords: Reduce Graphene Oxide, Structural Properties, Morpholog...