High Specific Capacitance Value Research Articles

PEMBUATAN ELEKTRODA KARBON DARI BIOMASSA SABUT KELAPA MUDA DENGAN AKTIVATOR KOH SEBAGAI APLIKASI SEL SUPERKAPASITOR

The supercapacitor is a storage device consisting of carbon electrodes, separator, electrolyte, and current collector. Carbon electrodes made from young coconut coir biomass with a mass ratio of 1:0.20 KOH activator have been successfully fabricated with a carbonization temperature of 550 °C and a physical activation temperature of 750 °C. Characterization of physical properties by measuring the density value showed that before and after pyrolysis decreased due to KOH activating agent. Furthermore, the electrochemical characterization using the voltammetry cyclic method showed the specific capacitance value to the scanning rate, where the highest specific capacitance value was 163.14 F/g with a scanning rate of 1 mV/s.

CoFe2O4 Hollow Spheres-Decorated Three-Dimensional rGO Sponge for Highly Efficient Electrochemical Charge Storage Devices.

The energy demand, the crisis of fossil fuels, and the increasing popularity of portable and wearable electronics in the global market have triggered the demand to develop high-performance flexible all-solid-state supercapacitors that are capable of delivering high energy at high power density as well as being safely entrenched in those electronics. Herein, we have designed a nanocomposite, 80CFhs-20rGOsp, which exhibits a high specific capacitance (CS) value of 1032 F g–1 at 3 A g–1. Utilizing this nanocomposite as the cathode and reduced graphene oxide sponge (rGOsp) as the anode, a flexible all-solid-state asymmetric device has been fabricated. In this device, poly(vinyl alcohol) (PVA) gel embedded with a mixture of 3 M KOH and 0.1 M K4[Fe(CN)6] was used as an electrolyte cum separator. The fabricated device showed the capability to deliver an energy density of 65.8 W h kg–1 at a power density of 1500 W kg–1 and retained its capability even after various physical deformations. The device also exhibited a long cycle life and retained ∼96% of its CS value after 5000 cycles. Moreover, the fabricated flexible all-solid-state device successfully illuminated light-emitting diodes, which proved its potential use in real-life supercapacitor applications. The obtained results revealed the excellent electrochemical performances of the fabricated device and rendered it a promising candidate in the energy sector.

Study of a complex of physical, crystallographic and mechanical properties of aluminum foil for electrolytic capacitors

The results of studies of the complex of physical, crystallographic and mechanical properties of aluminum foil for low-voltage and high-voltage electrolytic capacitors made of high-purity aluminum (99.99% Al) are presented. A comparative analysis of technological schemes for the production of foil for lowvoltage and high-voltage applications is given, the main differences in the schemes are shown, and the results are presented for the physical parameter: the value of specific capacitance, crystallographic characteristics (structure and predominant texture), mechanical properties (tensile strength and relative elongation). Low-voltage foil after electrochemical etching has a fine etching relief, which can cause the danger of its smoothing after the next operation of the electronic processing of molding — the creation of an oxide film of the dielectric. The required surface topography can be achieved at high total degrees of cold deformation, amounting to 98.8%, without intermediate annealing, obtaining a structure that is fibrous along the rolling direction with a predominant deformation texture {011} and pole density according to the results obtained (5.2). On the contrary, high-voltage foil after electrochemical etching has a rougher relief, and here the risk of surface smoothing after the molding operation is minimal, since the dielectric oxide film being formed is actually superimposed and duplicated along the trajectory of the resulting relief. The latter can be achieved by using a foil after recrystallization (intermediate) and final annealing to obtain an average grain size of about 72 microns, a predominantly near-cubic texture of the {420} foil, and a pole density of 2.4 obtained results. At the same time, high values of specific capacitance can be observed in the studied range: at forming voltages of 30 and 450 V, the value of specific capacitance is 1750 and 29 μF/dm2 for low-voltage and high-voltage foils, respectively.

On the performance of self-organized TiO2 nanotubes@MnOx as supercapacitor: Influence of the heat treatment, cathodic treatment, water aging, and thermal oxides

The performance of finely dispersed ε-MnO2 over two different self-organized TiO2 nanotubes (Ti/TiO2NT) substrates used as template, heat-treated in muffle furnace and microwave oven, was assessed as supercapacitor before and after a cathodic treatment (CT) to induce the formation of Ti(III)/oxygen vacancies. The pulsed MnO2 electrodeposition also led to the formation of Ti(III); however, the highest values of specific capacitance (∼200 F g–1 at 5 A g–1) were only attained when a CT (–1.6 V vs. Ag/AgCl/KCl 3 mol L–1 during 5 s using 0.5 mol L–1 of Na2SO4 as electrolyte) was applied regardless of the used substrate. X-ray photoelectron spectroscopy combined with the analysis of the time evolution of the electrochemical impedance (EI) showed that the hydroxylated surface, produced after CT by the reaction between adsorbed H2O and the unstable surface oxygen vacancies in the TiO2, led to a decrease of the charge transfer resistance and an increase of the TiO2NT@MnO2 film conductivity, indirectly measured through the evolution of the ohmic drop during galvanostatic experiments. The Ti/TiO2NT substrates and the thermally grown TiO2 oxide also exhibited similar EI performances before and after the CT, independently of the thermal treatment method. However, the total impedance of these samples was higher than that found for the composite electrode. This is an indication of the beneficial effect of the pulsed electrodeposition procedure in improving the conductivity of the TiO2NT substrate used successfully as template to produce nanosized MnO2 without binders.

Synthesis and characterization of a series of conducting polymers based on indole and carbazole.

A series of indole (In) and carbazole (Cz) derivative monomers have been synthesized, such as 4-[3-carbazolyl] indole (4In-3Cz), 5-[3-carbazolyl] indole (5In-3Cz), 6-[3-carbazolyl] indole (6In-3Cz), 7-[3-carbazolyl] indole (7In-3Cz). The comonomers synthesized by Stille coupling reaction were characterized by 1H-NMR and elemental analysis. Potentiodynamic method was used for electropolymerization of comonomers, Indole, Cz, and the mixture of In and Cz. Electrochemical activities of resulting P[4In-3Cz], P[5In-3Cz], P[6In-3Cz], P[7In-3Cz], polyindole (PIn), polycarbazole (PCz) and P[In-co-Cz] films were investigated comparatively by CV at different scan rates, electrochemical impedance spectroscopy (EIS) and spectroelectrochemical measurements. The ionization potentials, Ip, specific capacitance, Csp, and optical band gap, Eg, of copolymers were obtained from these measurements. In order to gain some preliminary information on the structure of the copolymers, DFT analysis was performed and dimers and tetramers were optimized. Results suggested that, in order to obtain an In-Cz copolymer with low oxidation potential and band gap, indole ring should be substituted through 5 position to the 3 position of Cz. If high specific capacitance value or high conductivity are desired, P[4In-3Cz] and P[6In-3Cz] are the best copolymers, respectively.

3D hierarchical flower-like CuCo2S4 as high energy density faradaic electrode

A direct one-step solvothermal approach was developed towards the preparation of flower-like CuCo2S4 (CCS) directly on the conductive Ni foam substrate. The morphological and structural studies of the synthesized materials were performed using XRD, HR-SEM and TEM studies, proves that the cubic spinel structured CCS flowers were decorated over the Ni foam substrate homogenously. The electrochemical performance of CCS was evaluated by cyclic voltammetry (CV), and galvanostatic charge-discharge (GCD). Benefiting from the synergistic effect between the two metal ions and special microstrual effect, resulted in an admirably high specific capacity value of 966.45C g−1 (1607.93F g−1) at 5 A g−1 current density, excellent rate capability at various applied current density (ranging from 5 A g−1 to 30 A g−1) and cycling stability upto 5000 cycles at very high current density of 5 A g−1 with 66.12% capacity retention. Hence, the binder free spinel CCS flowers demonstrated its penitential aspect as high-performance faradic electrode material for supercapacitors.

Fabrication of carbon-coated MnOx-Ni foam electrodes via pyrolysis of α-chitosan and their electrochemical performance

Carbon coated MnOx-Ni foam electrodes were successfully prepared using a combined process of hydrogel reaction followed by high-temperature pyrolysis under air or Ar gas conditions. The prepared samples were analyzed by various characterization tools. To evaluate the performances of the carbon coated MnOx-Ni foam electrodes as supercapacitors, cyclic voltammetry (CV), galvanostatic charge–discharge, electrochemical impedance spectroscopy (EIS) and cycle stability were also carried out. The carbon coated MnOx-Ni foam electrodes displayed supercapacitive behavior in 1.0 M KOH with a high specific capacitance value of 354.6 F g−1 at 10 mV s−1. The electrode also exhibited remarkable cycle stability. This research provides a valuable and effective approach to enhance the performance of materials applied as supercapacitors.

Effect of adding Ce on the optostructural and electrical properties of cubic CaSnO3

CaSnO3 and Ce doped CaSnO3 particles were synthesized by co-precipitation method. An X-ray diffraction study shows that the synthesized CaSnO3 particles belongs to orthorhombic structure and the crystalline peaks shift toward higher angle with increasing Ce concentration. The Fourier Transform Infrared Spectra witnessed the presence of Ca-O, Sn-O and Ce-O vibrations in the synthesized particles. The optical absorption is higher in the UV-region and the band gap energy is decreased from 4.3 eV to 3.2 eV. The photoluminescence spectra affirmed that the emission peak shifts toward the visible region during the incorporation of Ce. Scanning electron microscope images depicted the cubic block-like morphology with sharp edges. From the electrochemical measurements, 0.02 M Ce doped CaSnO3 electrode exhibited higher specific capacitance value of 916 F/g due to its lower charge transfer resistance value than that of 0.01 M and 0.03 M Ce doped CaSnO3.

ZnS-Co3S4 nanoscrubber synthesized by hydrothermal route for pseudo-supercapacitors

ZnS-Co3S4 Nanoscrubbers were prepared by hydrothermal routes and characterized by advanced techniques. The supercapacitance behavior of crystalline ZnS-Co3S4 nanoscrubber modified electrodes was examined using cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) techniques. As-prepared ZnS-Co3S4 nanoscrubbers have a high specific capacitance (Csp) value of 593 F/g at 0.5 A/g. The ZnS-Co3S4 modified electrode was found to be highly stable for 2000 cycles at 0.5A/g.

Green synthesis for the functionalization of reduced graphene and polyanline as efficient super capacitor application

A chemical polymerization of aniline is followed by a hydrothermal self-assembly of PANI and a graphene oxide (GO) dispersion in this two-step synthesis of polyaniline reduced graphene oxide (PANI/rGO). The systematic investigation of the component's influence on the composite porous structure, morphology and chemical properties. PANI/rGO electrode materials with specified physical and chemical properties, when employed as electrode materials for supercapacitors operating in an aqueous electrolyte, showed high specific capacitance values and excellent cyclic stability. The results show that one of the most important factors impacting composite electrochemical performance is the chemical composition of the PANI/rGO. The hydrothermal technique provides a wide range of synthesis options for creating hybrids with desirable physical and chemical properties. Furthermore, the PANI/rGO electrodes did not require an additional binder, making the fabrication process easier, emphasising its potential for use in flexible or asymmetric supercapacitors.

Carbon Nanotube Based Robust and Flexible Solid-State Supercapacitor.

All solid-state flexible electrochemical double-layer capacitors (EDLCs) are crucial for providing energy options in a variety of applications, ranging from wearable electronics to bendable micro/nanotechnology. Here, we report on the development of robust EDLCs using aligned multiwalled carbon nanotubes (MWCNTs) grown directly on thin metal foils embedded in a poly(vinyl alcohol)/phosphoric acid (PVA/H3PO4) polymer gel. The thin metal substrate holding the aligned MWCNT assembly provides mechanical robustness and the PVA/H3PO4 polymer gel, functioning both as the electrolyte as well as the separator, provides sufficient structural flexibility, without any loss of charge storage capacity under flexed conditions. The performance stability of these devices was verified by testing them under straight and bent formations. A high value of the areal specific capacitance (CSP) of ∼14.5 mF cm-2 with an energy density of ∼1 μW h cm-2 can be obtained in these devices. These values are significantly higher (in some cases, orders of magnitude) than several graphene as well as single-walled nanotube-based EDLC's utilizing similar electrolytes. We further show that these devices can withstand multiple (∼2500) mechanical bending cycles, without losing their energy storage capacities and are functional within the temperature range of 20 to 70 °C. Several strategies for enhancing the capacitive charge storage, such as physically stacking (in parallel) individual devices, or postproduction thermal annealing of electrodes, are also demonstrated. These findings demonstrated in this article provide tremendous impetus toward the realization of robust, stackable, and flexible all solid-state supercapacitors.

Layered nanoreactor assisted to produce B-doped and P-doped 3D carbon nanostructures for supercapacitor electrodes

In the use of the electric double layer capacitors (EDLCs) with carbon electrode materials, what remains an important technological challenge is that existing carbon electrodes suffer from low energy density and low volumetric capacitance, the today's need for making energy storage architectures. The incorporation of the n-type and/or p-type dopant elements in carbon structure may result in an enhancement in the capacitance. Accordingly, the idea to use the layered nanoreactors was applied to produce phosphorous-doped and boron-doped porous carbon nanostructures with high specific capacitance (CS) values when used in supercapacitor electrodes. So that, the best P-doped and B-doped carbon electrodes show the CS values of 322 and 275 F/g, respectively, at a current density of 1 A/g in the three-electrode system. A symmetric supercapacitor device made using the best doped carbon material (CG-P) showed a CS value of 163.2 F/g at a current density of 0.1 A/g. Herein, this work shows that the high values of CS for carbon materials are due to high accessible surface area, excellent pore size distribution, the presence and uniform dispersion of the dopant agents in carbon structures.

Designing of hierarchical lychee fruit-like cobalt-selenide heterostructures with enhanced performance for hybrid supercapacitors

Hierarchical porous structured active materials for energy storage devices could increase the surface area, stimulate the charge transport kinetics, and regulate the volume changes during the charge/discharge process. Moreover, the fabrication of heterostructures would increase the interfacial electric field and modify the electronic structure. The features of hierarchical porous heterostructures are more beneficial to enhance the electrochemical properties and robustness of electrode materials for supercapacitors (SCs). Herein, novel hierarchical lychee fruit-like cobalt-oxide@coblat-selenide heterostructure composites (LF-CoO@CoSe HSCs) composed of three-dimensional nanoparticles were prepared via an efficient single-step hydrothermal approach followed by calcination treatment. The LF-CoO@CoSe HSC-500 electrode exhibited a high specific capacity value of 341.6 mAh g−1 (2146.2 F g−1) at a current density of 2 A g−1 compared to the other electrodes annealed at 400 and 600°C (LF-CoO@CoSe HSC-400 (307.2 mAh g−1) and LF-CoO@CoSe HSC-600 (131.8 mAh g−1)), respectively. The LF-CoO@CoSe HSC-500 electrode delivered good cycling stability (77.5%). Furthermore, the pouch-type aqueous hybrid SC (AHSC) was constructed with LF-CoO@CoSe HSC-500 as a positive electrode and porous activated carbon as a negative electrode. The assembled AHSC device delivered maximum energy and power density values of 37.01 Wh kg−1 and 9490 W kg−1, respectively with superior cycling stability of 134% even after 5000 cycles. Furthermore, the fabricated AHSC device was successfully powered a mini light-emitting diode bulb and a timer display. The prepared composites could be an efficient electro-active material for high-capacity SC applications.

Synthetic melanin facilitates MnO supercapacitors with high specific capacitance and wide operation potential window

Although tremendous efforts have been devoted to manganous oxide (MnO)-based hybrid electrode materials, the rational design and facile preparation of high-performance MnO hybrid supercapacitors are still full of challenges, due to the inevitable agglomeration and limited stability of MnO within carbon matrixes. In this work, we developed a direct one-pot polymerization method to synthesize a series of Mn ion doped polylevodopa [P(L-DOPA)] synthetic melanin nanoparticles (Mn@SMNPs) for further transforming into small-sized hybrid carbon nanoparticles (MnO@CNPs, 20–80 nm) consisting of many stable Mn-related chemical bindings (C–N–Mn). The obtained MnO@CNPs electrode materials with physically spatial protection and well distribution of MnO could display high specific capacitance values (e.g., 545 F g−1 at 0.5 A g−1 in 6 M KOH electrolyte) within a wide operation voltage of 1.3 V. This work will continue to provide an inspiration towards the fabrication of the next-generation of high-performance synthetic melanin-based energy storage materials and devices.

Systematic Evaluation of Graphene-Based Materials By Hydrothermal Reduction for Supercapacitor Applications

A supercapacitor stores energy by electrical double-layer mechanism using electrostatic ion adsorption at the electrode surface and/or by reversible Faradaic charge transfer mechanisms. Graphene has been recognized as an excellent candidate for supercapacitors due to their high surface area (theoretical surface area: 2630 m2g-1) and excellent electrical conductivity.In this study, we report possible synergistic effects resulting from the combination of nitrogen doping and amine functionalization on rGO (reduced graphene oxide) for electrochemical supercapacitor performances. The specific capacitance of control rGO was 198 Fg-1 at a charge/discharge current density of 10 Ag-1. Compare to control rGO, the nitrogen doped rGO showed more pronounced electrochemical performance with higher specific capacitance values.

Shock waves induced enhancement of electrochemical properties of CoFe2O4 nanoparticles for energy storage applications

In the present work, we have performed Raman spectral analysis, scanning electron microscopic analysis and electrochemical measurements of dynamic shock wave loaded cobalt ferrite nano-particles (CoFe2O4 NPs) for different number of shock pulses as that of 0, 50,100 and 150 such that the respective observations have been investigated and the results are reported. Interestingly, among the four samples, 50 shocks loaded sample has homogenous particle size distribution and a high value of specific capacitance due to the occurrence of the shock wave-induced dynamic re-crystallization. Based on the observed electrochemical properties, shock wave loaded CoFe2O4 NPs are strongly suggested for energy storage applications.

N-doped sawdust-based activated biocarbons prepared by microwave-assisted heat treatment as potential electrode materials for supercapacitors

Microwave and conventional heating have been combined to obtain highly microporous nitrogen-doped activated biocarbons. In order to generate nitrogen groups bonded in different ways into the carbonaceous matrix, the modification with urea was performed at two different stages of processing, i.e., precursor or char. Additionally, the effects of chemical and thermal (physical) activation on the physicochemical parameters and capacitance behavior of the biocarbons prepared were tested. All the materials under investigation were characterized by elementary analysis, surface area measurements as well as estimation of the number of surface functional groups. Depending on the variant of preparation, the final products were microporous nitrogen-doped activated biocarbons of well-developed surface area ranging from 314 to 1483 m2/g, showing acidic or intermediate acidic–basic character of the surface and different contents of nitrogen functional groups, varying from 0.8 to 8.6 wt.%. Finally, the electrode materials were manufactured using prepared biocarbons and tested as components of symmetric supercapacitors, containing organic electrolyte. The electrochemical performance of these materials was investigated in Swagelok® type cells by using CV, GCD and EIS techniques. The results obtained in this study showed that incorporation of nitrogen and chemical activation of sawdust can led to activated biocarbons with very good electrochemical parameters. Most promising materials have exhibited high specific capacitance values (ca. 50 − 100 F g−1), good rate capability, and excellent cycling stability (ca. 86–88% capacitance retention) after thousands of GCD cycles.

One step synthesis of samarium vanadate nanorods for high performance supercapacitors

ABSTRACT Tetragonal SmVO4 nanorods were prepared by simple solvothermal route with various temperatures. An optimised SmVO4 sample was characterised through X-ray diffraction spectrum (XRD) and Micro-Raman spectroscopy. These results confirm that high crystallinity and pure tetragonal phase of SmVO4 can be achieved. For morphology analysis, scanning electron microscope (SEM), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray analysis (EDX) and selected area electron diffraction (SAED) techniques were performed. These results confirmed the rod shape SmVO4 nanoparticles with no impurities. For optical properties, UV-visible spectroscopy and photoluminescence (PL) techniques were performed. A broad absorption (290 nm – 330 nm) occurred in UV-Vis spectrum leads to multiple excitations and emissions at 542.7 nm, 600.5 nm and 643.7 nm with 4G5/2→6H5/2 (green), 4G5/2→6H7/2 (orange) and 4G5/2→6H9/2 (red), respectively. Finally, Vibrating sample magnetometer (VSM) study showed that the prepared SmVO4 nanoparticles possessed paramagnetic nature with high retentivity of 366.06 emu. Electrochemical performance of SV1 electrode shows pseudocapacitance nature with high specific capacitance value of 310 F/g (1 A/g) from GCD.

Supercapacitor Cell Electrodes Derived from Nipah Fruticans Fruit Coir Biomass for Energy Storage Applications using Acidic and Basic Electrolytes

The performance of the supercapacitor is influenced by the pore distribution on the electrode surface and the conductivity, mobility, ion size properties of the electrolyte to achieve a high specific capacitance value. Carbon electrodes are synthesized from Nipah fruit coir (NFC) biomass through a pre-carbonization process, chemical activation by varying the molarity of KOH of 0.2 M, 0.3 M, and 0.4 M, and the pyrolysis process. The electrochemical properties of supercapacitor cells are analyzed using the cyclic voltammetry method with an electrolyte solution of sulfuric acid and potassium hydroxide which is testing through an asymmetrical two-electrode system. The results showed that the increase in the performance of supercapacitor cells occurred in the electrolyte in an acidic environment with the highest specific capacitance value of 214.31 F/g compared to the electrolyte in an basic environment with the highest specific capacitance value of 164.54 F/g. The results of the analysis of electrochemical properties indicate that carbon electrodes made from Nipah fruit coir biomass can be a suitable material for energy storage applications.

Stereochemical, single crystal X-ray structural, Hirshfeld surface and cyclic voltammetric studies of N-cyclohexylcarbamoyl-3-isopropyl-2,6-bis(phenyl)piperidin-4-one and N-cyclohexylcarbamoyl-3,3-dimethyl-2,6-bis(4-fluorophenyl)-piperidin-4-one

• Twist boat conformation of N -cyclohexylcarbamoylpiperidin-4-one was proved by NMR and XRD. • Single crystal X-ray structural and Hirshfeld surface analysis of 1 and 2 were performed. • Computational and cyclic voltammetric studies were also performed. N- Cyclohexylcarbamoyl-3-isopropyl-2,6-bis(phenyl)piperidin-4-one (1) and N- Cyclohexylcarbamoyl-3,3-dimethyl-2,6-bis(4-fluorophenyl)piperidin-4-one (2) were synthesized and characterized by IR, 1 H NMR, 13 C NMR, HOMOCOSY, NOESY, HSQC and HMBC. Single crystal X-ray diffraction study was performed for 1 and 2 . Both the compounds (1 and 2) crystallized in triclinic crystal system with P -1 space group. From the XRD analysis results it is observed that the conformation of the heterocyclic ring in 1 and 2 is twist boat. The computational study was performed and the structures were optimized using DFT – B3LYP with the 6 - 31G basis set. Hirshfeld surface analysis was also carried out and the contributing intermolecular interactions which stabilizes the crystal structures are quantified. It exemplifies the predominant contribution of van der Waals interaction in the packing of both the crystal structures. Cyclic voltammetric studies were also performed and discussed. From the CV analysis it is observed that 2 exhibit the high specific capacitance value even at higher scan rate.