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Nickel-cobalt binary oxide/reduced graphene oxide (G-NCO) composite with high capacitance is synthesized via a mild method for electrochemical capacitors. G-NCO takes advantages of reduced graphene oxide (RGO) and nickel-cobalt binary oxide. As an appropriate matrix, RGO is beneficial to form homogeneous structure and improve the electron transport...
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Three-dimensional graphene-based aerogels (3D GAs), combining the intrinsic properties of graphene and 3D porous structure, have attracted increasing research interest in varied fields with potential application. Some related reviews focusing on applications in photoredox catalysis, biomedicine, energy storage, supercapacitor or other single aspect...
A new composite namely PEDOT/RGO/MnO2/Fe2O3 was successfully developed from mixed metal oxides (MnO2 and Fe2O3) incorporated with poly(3,4-ethylenedioxythiophene) (PEDOT) and reduced graphene oxide (RGO). The surface morphology of the prepared composite revealed that MnO2 and Fe2O3 particles were successfully coated on the wrinkles and curly like-s...
Here, we report the extraordinary electrochemical energy storage capability of NiMoO4@NiMoO4 homogeneous hierarchical nanosheet-on-nanowire arrays (SOWAs), synthesized on nickel substrate by a two-stage hydrothermal process. Comparatively speaking, the SOWAs electrode displays superior electrochemical performances over the pure NiMoO4 nanowire arra...
Flexible and transparent electrodes based on one-dimensional Ag nanowire@NiCo/NiCo(OH)2 core-shell nanostructures with tunable composition were fabricated by electrodeposition. The highly conductive Ag nanowire (NW) network was considered as effective electron transport channels, the NiCo/NiCo(OH)2 nanostructures could grow on the surface of the Ag...
The double ion-buffering reservoirs of asymmetric supercapacitors (ASC) have drawn enormous interest due to their excellent electrochemical performance. Herein, we have prepared the hierarchical porous sandwich-like Co3O4-rGO-CNT > N-PEGm (Co3O4-RGOC, in which rGO was short for reduced graphene oxide and CNT > N-PEGm was modified with methoxypolyet...
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... Whereas graphite Gband is the contribution of primary in-plane breathing mode of hexagonal sp 2 -carbon rings in graphite (E 2g phonons). [54,55] The slight broadening nature of Raman bands in the range of 300-700 cm −1 for NCO/GQDs composites signifies the interaction of carbon with metal oxides. A broad and low intensity peak observed at 1069 cm −1 can be assigned to Dʺ-band of carbonaceous traces in the composites. ...
For the sustainable growth of future generations, energy storage technologies like supercapacitors and batteries are becoming more and more common. However, reliable and high‐performance materials’ design and development is the key for the widespread adoption of batteries and supercapacitors. Quantum dots with fascinating and unusual properties are expected to revolutionize future technologies. However, while the recent discovery of quantum dots honored with a Nobel prize in Chemistry, their benefits for the tenacious problem of energy are not realized yet. In this context, herein, chemical‐composition tuning enabled exceptional performance of NiCo2O4(NCO)/graphene quantum dots (GQDs) is reported, which outperform the existing similar materials, in supercapacitors. A comprehensive study is performed on the synthesis, characterization, and electrochemical performance evaluation of highly functional NCO/GQDs in supercapacitors delivering enhanced energy efficiency. The high‐performance, functional NCO/GQDs electrode materials are synthesized by the incorporation of GQDs into NCO. The effect of variable amount of GQDs on the energy performance characteristics of NCO/GQDs in supercapacitors is studied systematically. In‐depth structural and chemical bonding analyses using X‐ray diffraction (XRD) and Raman spectroscopic studies indicate that all the NCO/GQDs composites crystallize in the spinel cubic phase of NiCo2O4 while graphene integration evident in all the NCO/GQDs. The scanning electron microscopy imaging analysis reveals homogeneously distributed spherical particles with a size distribution of 5–9 nm validating the formation of QDs. The high‐resolution transmission electron microscopy analyses reveal that the NCOQDs are anchored on graphene sheets, which provide a high surface area of 42.27 m²g⁻¹ and high mesoporosity for the composition of NCO/GQDs‐10%. In addition to establishing reliable electrical connection to graphene sheets, the NCOQDs provide reliable 3D‐conductive channels for rapid transport throughout the electrode as well as synergistic effects. Chemical‐composition tuning, and optimization yields NCO/GQDs‐10% to deliver the best specific capacitance of 3940 Fg⁻¹ at 0.5 Ag⁻¹, where the electrodes retain ≈98% capacitance after 5000 cycles. The NCO/GQD‐10%//AC asymmetric supercapacitor device demonstrates outstanding energy density and power density values of 118.04 Wh kg⁻¹ and 798.76 W kg⁻¹, respectively. The NCO/GQDs‐10%//NCO/GQDs‐10% symmetric supercapacitor device delivers excellent energy and power density of 24.30 Wh kg⁻¹ and 500 W kg⁻¹, respectively. These results demonstrate and conclude that NCO/GQDs are exceptional and prospective candidates for developing next‐generation high‐performance and sustainable energy storage devices.
... The removal of oxygen functional groups from the graphene structure reduces the graphene to increase the I D /I G ratio. 60,61 Conversely, increasing the I D′ /I G peak ratio from 0.6 before HER to 0.7 after CV cycling represents an increase in the defect concentration with doped atoms. Therefore, we can say that H + ions were adsorbed by the graphene surface and caused the D′ peak to increase during the HER analysis. ...
Herein, a layer of molybdenum oxide (MoOx), a transition metal oxide (TMO), which has outstanding catalytic properties in combination with a carbon-based thin film, is modified to improve the hydrogen production performance and protect the MoOx in acidic media. A thin film of graphene is transferred onto the MoOx layer, after which the graphene structure is doped with N and S atoms at room temperature using a plasma doping method to modify the electronic structure and intrinsic properties of the material. The oxygen functional groups in graphene increase the interfacial interactions and electrical contacts between graphene and MoOx. The appearance of surface defects such as oxygen vacancies can result in vacancies in MoOx. This improves the electrical conductivity and electrochemically accessible surface area. Increasing the number of defects in graphene by adding dopants can significantly affect the chemical reaction at the interfaces and improve the electrochemical performance. These defects in graphene play a crucial role in the adsorption of H⁺ ions on the graphene surface and their transport to the MoOx layer underneath. This enables MoOx to participate in the reaction with the doped graphene. N- and S-doped graphene (NSGr) on MoOx is active in acidic media and performs well in terms of hydrogen production. The initial overpotential value of 359 mV for the current density of −10 mA/cm² is lowered to 228 mV after activation. © 2023 The Authors. Carbon Energy published by Wenzhou University and John Wiley & Sons Australia, Ltd.
... The ratio of the D band to G band intensity, I D /I G , can be used to determine the defect content of GO [45]. The I D /I G ratio of GO is 0.95, while that of AGO3.0 is slightly higher at 0.98, indicating that the in-plane sp 2 domain size is smaller or that structural defects in graphene increase [46,47]. Consequently, the Raman spectra confirm the presence of GO in the sintered AGO composite. ...
Graphene oxide (GO) membranes have attracted considerable interest for hydrogen (H2) purification applications. However, the addition of GO into matrix materials to enhance the efficiency of H2 permeation remains a challenge. In this study, the fabrication of alumina/graphene oxide (AGO) composites containing varying contents of GO (0.5–3.0 wt.%) was investigated. The AGO composites were formed into pellets and sintered for 2 h at 1500 °C. Accordingly, the presence of GO in the membranes following sintering was confirmed by Raman spectroscopy. Additionally, the porosity of the AGO composites increased from 3.7% to 26.9% as the GO concentration increased from 0.5 wt.% to 3.0 wt.%. Furthermore, the average pore diameter of the AGO composites was in the range of 87–228 nm, and the pore size distribution was unimodal. The performance of the AGO membranes was investigated for the permeance of single gases H2 and N2 at 30 500 °C to evaluate their potential for H2 separation applications. The AGO membranes with a GO addition of 2.5 and 3.0 wt.% exhibited a high hydrogen permeance of 232–410 × 10−6 mol m−2 s−1 Pa−1, which was approximately 10 times greater than that of pristine Al2O3 membrane. Additionally, the ideal H2/N2 selectivity values ranged from 4.02 to 4.20. Furthermore, gas permeation through the AGO membrane was observed to follow the Knudsen diffusion mechanism.
... Meanwhile, the activity and stability of electrocatalysts were enhanced by using bimetallic materials. 36 Based on the abovementioned properties, bimetallic nickel-based materials have been employed in different energy conversion applications especially, supercapacitors, 37 and as anode materials in LIBs. 38 In addition, they have been used in electrocatalytic reactions for glucose, 39 urea, 40 and methanol 41 oxidation in alkaline medium. ...
The development of earth-abundant transition metal-based catalysts, supported by a conductive carbonaceous matrix, has received great attention in the field of conversion of formaldehyde derivatives into toxic-free species. Herein, we report a comprehensive investigation of bimetallic electrocatalyst activity towards the electrooxidation of formaldehyde. The bimetallic phosphate catalyst is prepared by co-precipitation of Ni and Mn phosphate precursors using a simple reflux approach. Then the bimetallic catalyst is produced by mixing the Ni/Mn with carbon fibres (CNFs). The structural properties and crystallinity of the catalyst were investigated by using several techniques, such as scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, and Brunauer Emmett-Teller theory. The system performance was studied under potentiostatic conditions. Some theoretical thermodynamic and kinetic models were applied to assess the system performance. Accordingly, key electrochemical parameters, including surface coverage (Γ) of active species, charge transfer rate (k s), diffusion coefficient of the formaldehyde (D), and catalytic rate constant (k cat) were calculated at Γ = 1.690 × 10-4 mmol cm-2, k s = 1.0800 s-1, D = 1.185 × 10-3 cm2 s-1 and k cat = 1.08 × 105 cm3 mol-1 s-1. These findings demonstrate the intrinsic electrocatalytic activity of formaldehyde electrooxidation on nickel/manganese phosphate- CNFs in alkaline medium.
... Apart from these single metal oxide electrode materials, mixed metal oxides, and metal oxide composites are also excellent for electrochemical applications. These materials generally contain a high theoretical capacitance arising from their multiple oxidation states, which in turn generate a huge pseudocapacitance effect and enhance charge storage [29,30]. In contrast, the values of their practical capacitance are quite lower than the theoretical values; this is due to the reduced activity and poor electroconductivity of a single oxide. ...
Hydrothermally synthesized electrodes of Co3O4@MnO2@NiO/GO were produced for use in supercapacitors. Graphene oxide (GO) was incorporated into the nanocomposites used for electrode synthesis due to its great surface area and electrical conductivity. The synergistic alliance among these composites and GO enhances electrode performance, life span, and stability. The structural properties obtained from the X-ray diffraction (XRD) results suggest that nanocomposites are crystalline in nature. The synergistic alliance among these composites and GO enhances electrode performance, life span, and stability. Performance assessment of these electrodes indicates that their characteristic performance was enhanced by C2+ radiation, with the uttermost performance witnessed for electrodes radiated with 5.0 × 1015 ions/cm2.
... However, poor conductivity of these materials may lead to electrolyte access lacking and slow charge separation, which in turn obstruct the values of specific capacitance. To alleviate these issues, various researchers across the globe studied that the incorporation of binary metal hydroxides with carbon derivatives such as carbon nanotubes (CNTs) [20,21], graphene and reduced graphene oxide has been made [22][23][24]. ...
In this work, NiMg@OH/reduced graphene oxide (rGO) nanocomposites are synthesised through microwave-assisted synthetic methodology using various reducing agents. The structural features and surface morphology of synthesised materials are fully examined with different spectroscopy and microscopy techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible spectroscopy (UV-Vis), Raman and Fourier Transform Infrared (FT-IR) spectroscopy. Further, this material was subjected to cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques for the systematic study of the properties and impact of reducing agents at various percentages of rGO on the specific capacitance of synthesised materials. The presence of rGO gradually improves the charge transfer process at the electrode/electrolyte interface. Among these nanocomposite materials, maximum specific capacitance of 650.31 F/g was observed for NiMg@OH-1.5 wt% rGO synthe-sised using NH 4 OH reducing agent in 6 M KOH electrolyte. Hence, the result signifies these composite materials are a promising candidate for supercapacitor applications. ARTICLE HISTORY
... The CV curves with a pair of well-defined redox peaks clearly confirm the battery-type performance of the NiMoO 4 (Fig. 8a), which can be attributed to the non-capacitive Faradic redox reactions (5-7). As the amount of Tween 80 increases, the area of the CV curve first increases and then decreases, indicating that too much Tween-80 is not conducive to ion diffusion of NiMoO 4 materials [32,33]. Compared with other samples, T 3 -NMO has the largest closed area and highest peak current which means the largest specific capacity. ...
Here, NiMoO4 was successfully synthesized via a mild hydrothermal method combined with annealing treatment. The effects of nickel sources and Tween 80 on the morphology and electrochemical performance of NiMoO4 electrode for hybrid energy storage device were investigated in detail. When nickel sulfate as a nickel source, NiMoO4 exhibited a one-dimensional needle structure and reached the best specific capacity of 498 C g⁻¹ at 1 A g⁻¹. Moreover, the different dosages of Tween 80 all improved the morphology and capacity of one-dimensional needle NiMoO4. When the dosage was 0.005 mol, NiMoO4 nanorods formed a flower-like morphology and a higher specific capacity of 754 C g⁻¹. Furthermore, we used the optimized NiMoO4 assembled a hybrid device which reached 68.36 Wh kg⁻¹ at a power density of 923 W kg⁻¹.
... Asymmetric supercapacitors have good practical applications [32]. In order to evaluate the practical application of the NiCoAl-LDHs electrode, an asymmetric supercapacitor device (C-NCA//AC) is assembled, in which the C-NCA electrode is used as the positive electrode and the activated carbon is used as the negative electrode. ...
In this paper, NiCoAl-LDHs were synthesized by hydrothermal method with polyvinyl alcohol, polyvinylpyrrolidone, cetyltrimethyl ammonium bromide, and sodium dodecyl sulfate as templating agents, and these materials directly grew on foamed nickel. The electrochemical performance of these materials was investigated by galvanostatic charge/discharge, cyclic voltammetry, and electrochemical impedance spectroscopy. The morphology and physicochemical properties of the materials were characterized by X-ray diffraction and scanning electron microscopy. The results showed that the NiCoAl electrode with the usage of 1.00 g polyvinyl alcohol, 1.00 g polyvinylpyrrolidone, 1.00 g cetyltrimethyl ammonium bromide, and 1.00 g sodium dodecyl sulfate and non-template agents showed high capacitance of 1413.2, 1553, 1648.4, and 1420 and 1068 F g⁻¹ at 1 A g⁻¹. It had excellent rate performance and cycle stability. After the 2000-cycle charge/discharge test at a current density of 10 A g⁻¹, the capacity of the materials’ retention rates was 82.68%, 80%, 88.4%, 90%, and 83.45%, respectively. An asymmetric supercapacitor (ASC) based on C-NCA electrode and activated carbon electrode achieved an excellent electrochemical property with the energy density of 75.55 Wh kg⁻¹ at the power density of 800 W kg⁻¹ and good cycling stability (retaining 89.87% after 2000 cycles). In summary, the prepared sample can be an ideal electrode material for a supercapacitor.
... As the amount of Tween80 increases, the area of the CV curve first increases and then decreases. It is that too much Tween80 is not conducive to ion diffusion of materials [45,46]. Among them, T 2 -NCA has the largest peak area, the highest peak current, and the largest specific capacitance. ...
Transition metal layered double hydroxides (LDHs) are one of the great potential electrode materials for pseudocapacitors. In this paper, NiCo-LDHs, NiAl-LDHs, CoAl-LDHs, and NiCoAl-LDHs were synthesized by hydrothermal method and these materials directly grew on foamed nickel. The electrochemical performance of these materials was investigated by galvanostatic charge-discharge test (GCD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The morphology and physicochemical properties of the materials were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The capacity of these materials at 1 A g⁻¹ was 894.4, 942.4, 885, and 1068 F g⁻¹, respectively. The capacity retention rates after 2000 cycles at 10 A g⁻¹ were 80.05%, 76.4%, 81.92%, and 83.7%, respectively. And then, we synthesized NiCoAl-LDHs with 0.002, 0.003, 0.004, and 0.005 mol Tween80 by the same experimental method. The influence on the morphology and electrochemical properties of NiCoAl-LDHs with different dosage of template agents was investigated. The results show that the capacity at 1 A g⁻¹ was 1336.4, 1433.2, 1430, and 1289.2 F g⁻¹, respectively. The capacity retention rates after 2000 cycles at 10 A g⁻¹ were 85%, 92%, 90%, and 88%, respectively. An asymmetric supercapacitor (ASC) was assembled with 0.003 mol Tween80 as positive electrode and activated carbon as negative electrode. The ASC device exhibited an ultra-high energy density of 89.79 Wh kg⁻¹ at power density of 775 W kg⁻¹ as well as long-term stability (86.02% of its initial capacitance retention at 10 A g⁻¹over 2000 cycles), outperforming most of LDH and metal oxides ASCs.
... The energy and power density of GH // GP is shown in figure 6. The energy density of GH // GP is 5.6 W h kg -1 at a power density of 226.5 W kg -1 and 3.1 W h kg -1 at 8446.2 W kg -1 , which is higher than reported in other literature [6]. ...
As a kind of new carbon materials, graphene has excellent performances such as superior conductivity, high specific surface area (2675 m ² g ⁻¹ ), and high cycle life. But graphene sheets are easily restacked by van der Waals interactions during the processes of preparation, storage, and application of them, which can loss ultrahigh specific surface area. The restacking of graphene sheets could be prevented by constructing graphene hydrogel (GH) or graphene composite. In this work, GH was prepared by a one-step hydrothermal synthesis reaction and glucose is used as a reducing agent, while graphene oxide/polyaniline (GP) composites was prepared by coating polyaniline on GO through in situ chemical polymerization of aniline. Then an asymmetric supercapacitor (GH//GP) was further assembled, where GH and GP are the positive and negative electrodes, respectively. The electrochemical properties of GH, GP, and GH//GP are studied using voltammetry and galvanostatic charge/discharge. The consequences indicate that the energy density of GH//GP reaches 5.6 W h kg ⁻¹ at power density of 226.5 W kg ⁻¹ and 3.1 W h kg ⁻¹ at energy density of 8446.2 W kg ⁻¹ .
