Use In High-performance Supercapacitors Research Articles

CuO nanoparticles mixed with activated BC extracted from algae as promising material for supercapacitor electrodes

The present analysis aims to use existing resources to lower the cost of electrodes and reduce environmental pollution by utilizing waste materials like green algae. In the present research, the hydrothermal carbonization technique was utilized to synthesize a nano sized CuO mixed with activated biochar (CuO@BC) extracted from red sea algae (Chlorophyta). The CuO@BC sample was extensively examined using several advanced physical techniques, such as UV/Visible spectroscopy, FTIR, XED, HRTEM, SEM, EDX, BET, and TGA. The HRTEM indicated that the size of the particles is 32 nm with a larger surface area and without aggregations. The BET analysis of CuO@BC indicates that the material contains pores of a relatively large size and with a pore diameter of about 42.56 A°. The electrochemical analysis of CuO@BC modified glassy carbon electrode CuO@BC/GCE has been investigated using CV, GCD, and EIS techniques. This CuO@BC/GCE shows excellent electrochemical features that are significant for energy storage applications. The CuO@BC/GCE showed a specific capacitance of approximately 353 Fg−1 which is higher compared to individual materials. Overall, the research outcomes suggest that the CuO@BC/GCE shows potential for use in high-performance supercapacitors as energy storage systems that are eco-friendly and sustainable.

NiCo-MOF Nanospheres Created by the Ultra-Fast Microwave Method for Use in High-Performance Supercapacitors.

Metal-organic frameworks-through the use of creative synthetic designs-could produce MOF materials with excellent porosity, stability, particle microstructures, and conductivity, and their inherent characteristics-including their porosity and controllable structure-may result in an immense number of prospects for energy storage. In this paper, a nanosphere-like NiCo-MOF was effectively manufactured via an ultra-fast microwave technique. Additionally, the ideal synthesis conditions of the NiCo-MOF were investigated by adjusting the microwave output power and microwave reaction time. Under the reaction conditions of a 600 W microwave and a 210 s microwave reaction time, the NiCo-MOF exhibited an excellent capacitance of 1348 F/g at a current density of 1 A/g and an 86.1% capacity retention rate at 10 A/g. In addition, self-assembled NiCo-MOF/AC asymmetric capacitors showed a splendid energy density of 46.6 Wh/kg and a power density of 8000 W/kg.

Oxygen-enriched hierarchical porous carbons derived from lignite for high-performance supercapacitors

Functional coal-based carbon materials with reasonable pore structure and surface properties have attracted extensive attention for use in high-performance supercapacitors. Herein, a ball milling-assisted bimetallic salt catalytic pyrolysis strategy was developed to prepare oxygen-doped hierarchical porous carbon (OHPC) derived from lignite. The optimized OHPC-1 shows a large specific surface area (1638 m2/g), rational pore structure distribution (mesopores account for 71.3%), and suitable oxygen doping, which ensure sufficient charge storage, rapid electrolyte ions diffusion, as well as the contributed pseudocapacitance. The obtained OHPC-1 exhibits a high specific capacitance of 283 F/g at 0.5 A/g in 6.0 M KOH electrolyte (operating voltage 1.2 V). The assembled OHPC-1//OHPC-1 symmetrical capacitor delivers a high energy density of 16.5 Wh/kg at the power density of 300 W/kg with long cycling stability. In sum, the proposed facile route for high-value utilization of lignite looks promising for the preparation of cost-effective porous carbons for high-performance supercapacitors.

Biomass valorisation of marula nutshell waste into nitrogen-doped activated carbon for use in high performance supercapacitors

This study reports on the valorisation of marula nutshell waste into a valuable electrode material for supercapacitors. Marula nutshell waste, a brown hard residue from marula fruits was valorised into a nitrogen-doped activated carbon (N-ACs) by KOH treatment and using melamine as a nitrogen source. The microporous and mesoporous nature of N-ACs exhibited a high surface area of 1427 m² g−1 and pore volume of 0.31 cm3 g−1. Three electrode measurements were done in 6 M KOH and 2.5 M KNO3 aqueous electrolytes, to examine the materials in alkaline and neutral medium. The N-ACs exhibited a capacitance of 350 F g−1 in 6 M KOH and 248 F g−1 in 2.5 M KNO3 electrolyte. Due to low toxicity and wider operating voltage (∼1.8 V) of 2.5 KNO3, the material was further analysed in a symmetric device. The high surface area, the defects, and the high content of nitrogen (5.1%) revealed that the material produced an outstanding energy density of 17.2 Wh kg−1 and a power density of 448.7 W kg−1 in 2.5 M KNO3 electrolyte. The conversion of marula nuts waste into N-ACs thus provide a means of converting biomass waste into a useful energy storage material for supercapacitors.

Temperature-modulated synthesis of vertically oriented atomic bilayer graphene nanowalls grown on stainless steel by inductively coupled plasma chemical vapour deposition

It is now clear that growing flat graphene nanostructures from the gas phase on planar substrates is possible. One of the keys to success —particularly in producing a very large specific surface in a reduced space— is the use of 3D carbon nanostructures (i.e., vertical graphene nanowalls, VGNWs) over a planar substrate as a growth template for the deposition of electrochemically active materials (as, for example, transition metal oxides (TMO)). Vertical graphene nanowalls, also known as petal-like, vertical graphene flakes or vertical graphene, can achieve a very large specific surface area of 1100 m2/g, which is comparable to or greater than that of carbon nanotubes —the reference material for its use in high-performance supercapacitors or in other energy-related applications requiring a large active surface area. Vertical graphene nanowalls also exhibit high vertical and in-plane electrical conductivity when grown on metal electrodes, which benefits their use in electrochemical applications. Here, we focus on the growth of VGNWs on flexible stainless-steel substrates (SS310), in principle suitable for applications to electrodes of electrochemical systems (batteries, supercapacitors, catalysts), by inductively coupled plasma chemical vapour deposition (ICP-CVD), from methane as a carbon precursor, in a wide range of temperatures (575 to 900 °C). We will discuss the effect of growth temperature on morphological and structural characteristics of VGNWs based on the results of Raman spectroscopy and field emission scanning electron microscopy (FE-SEM) analysis. Because the nanostructures of graphene nanowalls reported to date are, for the most part, based on multi-layered graphene, here we seek to highlight the effect of temperature on the number of atomic layers of VGNW. In the 700–750 °C range, and under the plasma conditions explored, vertical graphene nanowalls are bilayer, which is foreseen to directly affect the magnitude of the VGNW specific surface.

Preparation of cyclodextrin polymer-functionalized polyaniline/porous carbon composites for use in high-performance supercapacitors

• Pani can be polymerized on PC surface through host–guest interactions. • Ordered polymerization of Pani on PC is achieved by cyclodextrin polymer. • The products exhibit good specific surface area and high specific capacitance. Ordered polymerization of polyaniline (PANI) on porous carbon (PC) was achieved using cyclodextrin polymer (CDP)-functionalization (CDP/PC) on PC. PANI can be polymerized on PC surface through host–guest interactions between aniline monomers and the CDP to form the CDP-PANI/PC composite. CD modification induced the ordered polymerization of aniline monomers. So CDP-PANI/PC exhibited remarkable specific capacitance (739.2 F·g −1 at 1 A·g −1 ) and high rate capability (516 F·g −1 at 10 A·g −1 , retaining 69.8% of its original capacitance) in a three-electrode system. A symmetrical supercapacitor device assembled from CDP-PANI/PC electrodes retained over 81 % of its initial capacitance after 5000 cycles at 5 A·g −1 .

Hierarchically designed NiCo2O4 nanowire/NiCo2O4 nanosheet electrodes for high-performance energy storage applications

A NiCo2O4 nanowire/NiCo2O4 nanosheet composite with a nanostructure was fabricated on nickel foam for use in high-performance supercapacitors by using two-step solution-based approaches such as hydrothermal and chemical bath deposition methods. In this study, the supercapacitive performance of NiCo2O4 nanowires was compared with that of NiCo2O4 nanowire/NiCo2O4 nanosheet arrays in a 2 M KOH electrolyte. The electrochemical study shows that NiCo2O4 nanowires/NiCo2O4 nanosheets exhibit higher electrochemical performance than NiCo2O4 nanowires. The NiCo2O4 nanowires/NiCo2O4 nanosheets (1866 F/g) have a high specific capacitance than NiCo2O4 nanowires (1023 F/g), at 2 A/g. Further, NiCo2O4 nanowire/NiCo2O4 nanosheet arrays show high electrochemical cycling stability of 94.8% over 5,000 cycles. This enhanced electrochemical performance is attributed to the hierarchically arranged morphology of the NiCo2O4 nanowire/NiCo2O4 nanosheet composite, which provides a large number of active sites for redox reactions, and fast ion-transfer ability.

Electrochemical Development and Characterization By SECM of 2D Carbon-Based Materials Architectured for Energy Storage and Conversion

With the fastly-growing social and commercial demands for portable electronic devices and the need for developing environmentally friendly high-power energy sources, new non-critical, non-toxic materials are currently being widely studied [1]. Electrochemical Double Layer Capacitors, also termed as supercapacitors, store energy electrostatically by charge separation at the high-surface-area porous carbon / electrolyte interface, by charging the electrochemical double layer [2]. Carbon-based materials are the most widely used electrode materials for EDLCs because of their desirable physical-chemical properties and low cost. Out of the various carbon structures explored as electrode materials, graphene appears to be a promising candidate thanks to its key properties [3].In this work, in-depth electrochemical characterizations of 2-Dimensional graphene-based materials was achieved using Scanning Electrochemical Microscopy (SECM) technique to study local electrochemical properties: ionic transport and charge transfer properties. 2D carbon materials with tuned interlayer distance were prepared by bridging reduced graphene oxide (rGO) sheets using hexanediamine electroactive molecules acting as pillars. Pillared and non-pillared porous graphene hydrogel (6GH and GHG respectively) composed were also synthetized and tested. Those measurements gave insights about the electroactivity and conductivity of the material’s surface. Also, the influence of the nature and lengths of the pillar on the electrochemical performance have been studied. Preliminary results using conventional electrochemical techniques show that the specific capacitance of raw GHG (170 F g-1) was reduced down to 70F g-1 when adding 6 carbons-hexanediamine pillars during its hydrothermal synthesis to prepare the 6GH (pillared graphene hydrogel). For the rGO, the addition of pillars with different lengths resulted in an increase of specific capacitance from 100 F g-1 to rGO to 140 F g-1 for rGO pillared with 7 atoms pillar diamine pillar (7RP) and 130 F g-1 for rGO pillared with 8 atoms diamine pillar (8RP) .Then, SECM experiments in feedback mode allowed for a fast comparison of the change in local electrochemical activity for the different surfaces through redox reactions between the tip and the electrode surface for all developed materials. Fitting measured approach curves to simulated ones can be used to estimate rate coefficients, as suggested by Chang, Mirkin and Bard [5]. The effective rate coefficient (keff) values for the mediator regenerating surface reaction were estimated using Wittstock's method by fitting the approach curves recorded at different positions. A 10µm diameter platinum-disc microelectrode was the tip connected to the Bio-Logic SECM-150 bipotentiostat and responsible for the approach curve measurement. For the GHG, it was found a 2.3 10-2 cm s-1 effective constant, which is reduced to 1.6 1.8 10-2 cm s-1 for the 6GH. For the rGO, the keff has the value of 3.3 10-2 cm s-1. The next step is to define the effective constant for the pillared rGO 7RP and 8RP. This study contributed to define the key characteristics allowing for the use of electrodes for supercapacitors offering optimal performance in energy density and power density.1- Zhang, Li Li; Zhao, X. S. Carbon-based materials as supercapacitor electrodes. , 38(9), 2520–0, 2009.2- Jiang Yang, Sundaram Gunasekaran. Electrochemically reduced graphene oxide sheets for use in high performance supercapacitors,Carbon, 2013.3- Zhu, Y.; Murali, S.; Stoller, M. D.; Ganesh, K. J.; Cai, W.; Ferreira, P. J.; Pirkle, A.; Wallace, R. M.; Cychosz, K. A.; Thommes, M. Carbon-Based Supercapacitors Produced by Activation of Graphene, 2011. 4-TAKAHASHI, Yasufumi. Development of High-Resolution Scanning Electrochemical Microscopy for Nanoscale Topography and Electrochemical Simultaneous Imaging. Electrochemistry, 2016.5- C. Wei, A.J. Bard, M.V. Mirkin, Scanning electrochemical microscopy. 31. Application of SECM to study of charge transfer processes at the liquid/liquid interface, J. Phys. Chem. 99 Figure 1

Micro/mesopore carbon spheres derived from sucrose for use in high performance supercapacitors

Micro/mesopore carbon spheres derived from sucrose for use in high performance supercapacitors

Micro/mesopore carbon spheres derived from sucrose for use in high performance supercapacitors

Micro/mesopore carbon spheres for supercapacitor application were prepared by hydrothermal carbonization followed by KOH/NaOH activation using sucrose as the carbon precursor. The effects of the KOH and NaOH activation parameters on the specific surface area, pore size distribution and electrochemical performance of the carbon spheres were investigated. Results indicate that the use of NaOH leads to the development of mesopores while the use of KOH increases the specific surface area and micropore volume. The pore size distribution of carbon spheres could be adjusted by varying the relative amounts of the reagents during the activation. Using a NaOH/KOH mass ratio of 2:1 and a reagent/carbon sphere mass ratio of 3:1, good capacitance and rate performance of the supercapacitor electrode in both 6 mol L-1 KOH aqueous electrolyte and 1 mol L-1 MeEt3NBF4/propylene carbonate electrolyte were achieved. The prepared activated carbon shows a high capacitance of 235 F g-1 at 0.1 A g-1 and a capacitance retention of 81.5% at 20 A g-1 in the 6 mol L-1 KOH aqueous electrolyte, the symmetric device assembled by 1 mol L-1 MeEt3NBF4/propylene carbonate electrolyte delivers the maximum energy density of 30.4 Wh kg-1 and the highest power output of 18.5 kW kg-1, respectively.

Highly Flexible and Tailorable Cobalt-Doped Cross-Linked Polyacrylamide-Based Electrolytes for Use in High-Performance Supercapacitors.

A novel hydrogel polymer electrolyte was prepared by incorporation of 1,4-butanediol diglycidyl ether (BG) to cross-linked polyacrylamide (PAM). The electrolyte (PAMBG) was modified with cobalt (II) sulfate with various doping ratios (PAMBGCoX) to increase the capacitance by increasing faradaic reactions. The supercapacitor device assembly was performed by using active carbon (AC) electrodes and hydrogel polymer electrolytes. The specific capacitance of the PAMBGCo5 device indicated 130 F g-1 , which is at least a seven-fold improvement due to the insertion of Co as a redox component. The electrolyte device, PAMBGCo5, displays superior performance having an energy density of 38 Wh kg-1 at a power density of 500 W kg-1 . Additionally, with the same hydrogel, the device performed 10,000 galvanostatic charge-discharge cycles via retaining 91% of the initial capacitance. A cost-effective electrolyte, PAMBGCo5, was tested in a carbon-based supercapacitor under bent and twisted conditions at various angles, confirming the robustness of the device.

Construction of three-dimensional all-carbon C60/graphene hybrids and their use in high performance supercapacitors

Control of the three-dimensional (3D) pore structure of all-carbon C60/graphene hybrids was conducted by introducing C60 molecules into graphene laminates by a simple hydrothermal method to improve their performance as electrodes in supercapacitors. Results indicate that the strong π-π interaction between carbon hexagons in C60 and graphene skeletons favors the self-assembly of the 3D pore structure of the C60/graphene hybrids under hydrothermal conditions. The addition of C60 molecules gives the hybrids a hierarchical pore structure and redox-active sites, which contribute remarkably to the improved electrochemical performance. A specific capacitance of 332.3 F·g-1 at a current density of 1 A·g-1 was obtained in a 6 mol·L-1 potassium hydroxide solution for a hybrid optimized by an orthogonal experimental design method, which is 54.5% higher than that of the graphene without C60. This finding indicates that the all-carbon hybrids may be used as more competitive and promising electrodes for the fabrication of high performance supercapacitors.

Role of Reduced Graphene Oxide Binder for Supercapacitor with Commercial-Level Mass Loading

Effective specific-surface-area (SSA) utilization of active materials and rapid ion/electron transport within electrodes with commercial-level mass loadings (>10 mg cm−2) are critical for the practical applications of supercapacitors (SCs). In this study, we demonstrate a versatile method to achieve high-performance SCs for commercial applications using biomass-derived porous activated carbons (PACs) as the main active material and reduced graphene oxide (rGO) as a multifunctional conductive binder that holds the PACs in an interconnected-network structure across the entire electrode. In the resultant PAC–rGO, the rGO sheets not only effectively maintain the high SSA of the PACs to provide abundant active sites in contact with electrolyte ions but also provide conductive passages through which ions can easily pass to reach the PAC surfaces. Functional groups on the rGO binder also promote substantial ion-adsorption capability by improving electrolyte wettability. Benefiting from the multifunctional roles of the rGO binder, the obtained electrode exhibits outstanding specific and areal capacitances as well as excellent rate capability and cycling performance, even with a high mass loading of 12 mg cm−2, demonstrating its strong potential for use in high-performance SCs.

Direct laser writing of MnO2 decorated graphene as flexible supercapacitor electrodes

Manganese oxides/graphene is an electrode material currently under consideration for use in high-performance supercapacitors (SCs). The conventional, widely used wet chemical methods for preparing MnO2/graphene are tedious and consume large quantities of strong reduction/oxidation reagents. The resulting powder composites require adhesives to form a suitable electrode. In the present study, we report on a method for synthesizing MnO2/graphene composite electrodes using a second laser irradiation employing a laser of the polyether ether ketone. This simple and environmentally friendly method allows the patterning of electrodes together with the synthesis of the active materials. The MnO2/laser-induced graphene (LIG) electrode exhibited a high capacitance of 48.9 mF cm−2, which is about 2.4 times greater than a pure LIG electrode. Assembled all solid micro-supercapacitors (MSCs) containing the novel LIG electrodes delivered both high energy density (3.1 μWh cm−2) and power density (2.5 mW cm−2). These MSCs exhibited a capacitance retention of 94.3% over 3000 cycles, at a current density of 0.5 mA cm−2. The electrochemical performance was almost unaltered by bending the MSC to 150°. This method of synthesizing high-performance flexible electrodes is important for future development of wearable electronics.

An asymmetric supercapacitor based on a NiO/Co3O4@NiCo cathode and an activated carbon anode

Pseudocapacitive metal oxide active materials are promising for use in high performance supercapacitors. However, their poor electrical conductivity greatly hinders their practical application. We formed NiO and Co3O4 active materials on the surface of a highly conductive NiCo nanowire membrane current collector by a simple air oxidation method to fabricate a self-supported flexible NiO/Co3O4@NiCo electrode. This significantly improves electron transport at the interface between the current collector and the active NiO/Co3O4. Furthermore, the reticular nanowire network facilitates ion transportation and releases strain caused during charge and discharge. Due to this unique structural characteristic, the NiO/Co3O4@NiCo electrode delivers a high specific capacitance of 1.36 F cm−2 at a current density of 5 mA cm−2, and excellent cycling stability with a capacitance retention of 96.95% after 10 000 cycles. An asymmetric supercapacitor was assembled using the NiO/Co3O4@NiCo as the cathode and an activated carbon electrode as the anode, which delivered an energy density of 0.32 mWh cm−2 at a power density of 8 mW cm−2. Even at a high power density of 40 mW cm−2, an energy density of 0.17 mWh cm−2 was achieved, suggesting its promising use as an efficient electrode for high performance supercapacitors.

Sustainable nitrogen-doped carbon electrodes for use in high-performance supercapacitors and Li-ion capacitors

Supercapacitor and Li-ion capacitor assembled by well-matched carbon anode and cathode obtained from ginger straw, both exhibiting remarkable energy and power combinations.

Graphene aerogel modified with a vanadium nitride film by a sputtering method for use in high-performance supercapacitors

A novel three-dimensional (3D) hybrid electrode based on graphene aerogel (GA) modified with a vanadium nitride (VN) film by a sputtering method has been prepared. This method allows for better structural integration of GA and the VN film, resulting in enhanced electrochemical properties. The as-prepared VN/GA shows excellent electrochemical performance, with a maximum specific capacitance of 236.5 F g−1 at a charge/discharge current density of 0.5 A g−1, a good rate capability of 86.3% at 1 A g−1, and 91.8% specific capacitance retention after 1000 cycles. These parameters are superior to those reported for conventional GA- and VN-based electrodes. These findings open a new pathway for the fabrication of novel aerogel-based electrode materials for high-performance supercapacitors.

MnO2@NiO nanosheets@nanowires hierarchical structures with enhanced supercapacitive properties

Transitional metal oxides are demonstrated as promising candidates for pseudocapacitive electrode materials for use in high-performance supercapacitors. Here, we report a rational design of the MnO2@NiO nanosheets@nanowires hybrid structure. The as-prepared hierarchical structure shows highly uniformity and interconnection between ultrathin MnO2 nanosheets and NiO nanowires. The well-designed MnO2@NiO is directly used as binder-free electrode and exhibits a high specific capacitance (374.6 F g−1 at a current density of 0.25 A g−1; areal capacitance of 1.3 F cm−2), good rate capability, and excellent cycling stability (92.7% capacitance retention after 5000 charge/discharge cycles). An asymmetric supercapacitor (ASC) is assembled using the MnO2@NiO as the positive electrode and activated microwave exfoliated graphite oxide as the negative electrode. The assembled ASC shows excellent electrochemical performance with an energy density of 15.4 W kg−1 and a maximum power density of 9360 W kg−1. These analytical and experimental results clearly indicate the advantages of multicomponent hierarchical core–shell structure for engineering high-performance electrochemical capacitors.

Mn3O4-polyaniline-graphene as distinctive composite for use in high-performance supercapacitors

Introduction of graphene into the stable matrix of Mn3O4-polyaniline composite leads to supercapacitor electrode that can deliver specific capacitance >1000 F g−1. This is nearly double the value, which is observed in conventional type Mn3O4-polyaniline composite that is able to deliver ~500 F g−1, at a scan rate of 5 mV s−1 in the voltage window −1 to 1 V. This value is also much greater than those obtained in most of the niche carbon or transition metal oxide based supercapacitors. Cycling studies, carried out at a current density 25 A g−1 and for 3000 cycles, indicated that the composite continue to retain nearly ~97% of the initial capacitance. The enhancement can be explained in terms of the connected percolated conductive path, which originates due to the dispersed graphene sheets.

CuCo2O4 nanowire arrays wrapped in metal oxide nanosheets as hierarchical multicomponent electrodes for supercapacitors

Herein, we report the rational design and fabrication of multicomponent, hierarchical CuCo2O4 nanowire arrays wrapped with metal oxides (NiO, Co3O4 and MnO2) nanosheets for use in high-performance supercapacitors. Among all the composite electrodes prepared, the CuCo2O4@NiO electrode exhibits the best electrochemical behavior with a high areal capacitance of 2.3 F/cm2 at 2 mA/cm2 and excellent cycling stability. The asymmetric supercapacitor with CuCo2O4@NiO as the positive electrode shows a superior specific capacitance of 124.6 F/g at 1 A/g, exceptional energy density of 38.9 Wh/kg at 750 W/kg, and long cycle life with ∼81.3% capacitance retention after 6000 cycles. The results indicate that the CuCo2O4@NiO electrode shows great potential for high-performance electrochemical energy storage.