Supercapacitor performance of activated carbon derived from rotten carrot in aqueous,organic and ionic liquid based electrolytes

In this work, we report the synthesis of porous activated carbon (AC). AC was derived from rotten carrot, at different values of activating temperature under inert atmosphere, employing chemical activation method and ZnCl₂ as activation agent. On the basis of results observed by surface area and pore size analysis, effect of activation temperature on synthesized AC was determined. Other material properties such as morphology, thermal stability, vibrational response, and crystal structure of prepared AC were studied using standard techniques of material characterization. Further, the electrochemical performance of synthesized AC was studied as an electrode, in aqueous, organic and ionic liquid based electrolyte. It was found that the synthesized AC based electrode exhibits highest specific capacitance (135.5?F?g^?1 at 10?mHz) in aqueous electrolyte and highest specific energy (29.1?Wh?kg^?1 at 2.2?A?g^?1) and specific power (142.5?kW?kg^?1 at 2.2?A?g^?1) in ionic liquid based electrolyte. This shows the suitability of synthesized material for use in energy storage applications.     

Pomegranate rind-derived activated carbon as electrode material for high-performance supercapacitors

In this paper, activated carbon materials were synthesized from pomegranate rind through carbonization and alkaline activation processes. The effects of pyrolytic temperature on the textual properties and electrochemical performance were investigated. The surface area of the activated carbon can reach at least 2200 m² g^?1 at different pyrolytic temperatures. It was found that, at the range of 600–900 °C, decreasing the carbonization temperature leads to the increase of t-plot micropore area, t-plot micropore volume, and capacitance. Further decreasing the carbonization temperature to 500 °C also leads to the increase of t-plot micropore area and t-plot micropore volume, but the capacitance is slightly poorer. The activated carbon carbonized at 600 °C and activated at 800 °C possesses very high specific area (2931 m² g^?1) and exhibits very high capacitance (～268 F g^?1 at 0.1 A g^?1 and ～242 F g^?1 at 1 A g^?1). There is no capacitance fading after 2000th cycle.     

Electrochemical oxidation of a carbon black loaded polymer electrode in aqueous electrolytes

The suitability of a polymeric composite material for use as part of an anode structure in a cathodic protection system has been examined. The composite material was a conductive blend (volume resistivity typically 1.5 Ω cm) of carbon black in a polyethylene binder. A long operational lifetime for the material demands that the rate of carbon loss must be low. In the work reported here, electrochemical and in situ analytical techniques were employed to characterise the performance of the material over a wide range of anodic current densities in a variety of aqueous electrolytes. The predominant anodic electrochemical reaction on the polymeric material is CO₂ formation in acid and neutral solutions, which causes loss of carbon from the surface and the development of a non-conducting layer of polyethylene. The characteristics of the reaction suggest that it occurs via the discharge of H₂O. In alkaline pH, however, the anodic reactions are more complex. A high OH⁻ concentration (pH 12 or higher) favours the formation of oxygen rather than CO₂, particularly at low anodic potentials. The presence of CO₃ ²⁻ in the electrolyte catalyses the evolution of oxygen at pH values as low as 9. The electrochemical formation of oxygen always occurs in parallel with the generation of some humic acid in the solution. Received: 23 July 1998 / Accepted: 17 November 1998     

Persulfate treatment as a method of modifying carbon electrode material for aqueous electrochemical capacitors

The activated carbon was modified by the wet method with a solution of ammonium persulfate at room temperature with different times. Kinetics studies showed that the modification took place mostly during the first 60 min of the process. The physicochemical properties of the obtained carbon were evaluated by thermogravimetric studies, Raman and FTIR spectroscopy, elementary and BET analyses. Furthermore, the fabricated material was applied in symmetric capacitors operated on the three aqueous electrolytes (1 M H₂SO₄, 6 M KOH and 1 M Na₂SO₄). Mild conditions of the modification process are optimal to obtain electroactive groups on the carbon surface, which make this material useful in a supercapacitor application. In our studies, we noticed that this type of functional groups mainly appears on the surface of the activated carbon, in the first oxidation stage. With prolonged oxidation, they may transform into undesirable groups. The results show that this kind of modification improves the capacity of all the tested supercapacitors. It was connected mainly with an increase of the carbon material’s wettability and in the case of capacitor operated in acid and base electrolytes due to a redox reaction of oxygen functional groups.

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Graphical abstract Persulfate treatment of carbon material.

     

Preparation of activated carbon from Turbinaria turbinata seaweeds and its use as supercapacitor electrode materials

Turbinaria turbinata brown seaweeds were tested as carbon electrode material in symmetric, electrochemical supercapacitors. The electrochemical properties of the carbon materials were characterised for their application as supercapacitors using cyclic voltammetry, galvanostatic charge/discharge method and electrochemical impedance spectroscopic analyses. Our initial results showed that the optimal behaviour was obtained for the sample prepared by pyrolysis at 800 °C. The average surface area of the carbon was 812 m²/g. Electrochemical tests with an organic electrolyte gave the following interesting results: a capacitance of 74.5 F/g, a specific series resistance of 0.5 Ω cm² and an ionic resistivity of 1.3 Ω cm². These results show the promising capacitive properties of carbon derived from seaweeds and their application in electrochemical supercapacitors.     

Glassy carbon as electrode material in electro- analytical chemistry

The review is based on a literature search through Chemical Abstracts and the Science Citation Index. The topics covered are: chemical and electrochemical aspects of the glassy carbon/electrolyte interface for both aqueous solutions and non-aqueous electrolytes; analytical applications of glassy carbon electrodes, including voltammetry, stripping voltammetry, amperometry coulometry, potentiometry and chronopotentiometry; flow-through detectors; chemically modified glassy carbon electrodes; electrosynthesis; and pretreatment techniques.     

A novel carbon electrode material for highly improved EDLC performance

Porous materials, developed by grafting functional groups through chemical surface modification with a surfactant, represent an innovative concept in energy storage. This work reports, in detail, the first practical realization of a novel carbon electrode based on grafting of vinyltrimethoxysilane (vtmos) functional group for energy storage in electric double layer capacitor (EDLC). Surface modification with surfactant vtmos enhances the hydrophobisation of activated carbon and the affinity toward propylene carbonate (PC) solvent, which improves the wettability of activated carbon in the electrolyte solution based on PC solvent, resulting in not only a lower resistance to the transport of electrolyte ions within micropores of activated carbon but also more usable surface area for the formation of electric double layer, and accordingly, higher specific capacitance, energy density, and power capability available from the capacitor based on modified carbon. Especially, the effects from surface modification become superior at higher discharge rate, at which much better EDLC performance (i.e., much higher energy density and power capability) has been achieved by the modified carbon, suggesting that the modified carbon is a novel and very promising electrode material of EDLC for large current applications where both high energy density and power capability are required.     

Thin layer of Ni-modified 13X zeolite on glassy carbon support as an electrode material in aqueous solutions

A new type of an electrode material, zeolite modified by the incorporation of Ni or NiO clusters into its cavities, was synthesized by multiple impregnation of zeolite 13X with a Ni-acetylacetonate solution followed by solvent evaporation and thermal degradation of the nickel compound. Samples with a Ni/13X mass ratio within the range 0.2–1.0 were synthesized. Modification by both Ni and NiO clusters, depending on whether the atmosphere was reducing (H₂) or oxidizing (air), respectively, was used to finish the sample. After modification, the zeolite kept its original crystallographic structure, as proven by X-ray diffractommetry. The dimensions of the incorporated clusters were limited by the diameter of the zeolite cavities (reaching 1.3 nm). This material, homogenized with 10 wt % of nanodispersed carbon, was bonded in the form of a thin layer to a glassy carbon disc by means of Nafion and used as an electrode material in an aqueous 0.1 M NaOH solution. The cyclovoltammograms of this thin-layer electrode resemble those of a smooth nickel electrode in alkaline solutions. The text was submitted by the authors in English.     

Modifying transparent electrode with conjugated organic semiconductor hole transport material as interface for enhancing performance of organic solar cell

Indium tin oxide (ITO) is used as a substrate was covered with 4-[4-(4-methoxy-N-naphthalen-2-ylanilino) phenyl] benzoic acid (MNA) as a self-assembled monolayer (SAM). Poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6) C₆₁ (PCBM) were mixed and used as a donor–acceptor in organic solar cell (OSC). The MNA (SAM) layer is used as an interface instead of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS) for hole injection. The HOMO-LUMO energy level of MNA-SAM molecule and the electronic charge distribution were calculated theoretically using Chemissian software. The HOMO-LUMO energy level of the MNA is calculated as E_HOMO = ?5.10 eV and E_LUMO = ?1.60 eV. The OSC modified with MNA showed an efficient performance in the absence of PEDOT: PSS as hole transport layer. The annealing of the ITO/SAM/P3HT: PCBM films at different temperatures are also investigated to study the effect of reducing defects. The interface structures of the organic semiconductor layer on ITO were characterized by Atomic Force Microcopy (AFM). In addition, Kelvin Probe Microscopy (KPM) is used to understand how the annealing changes the surface potential energy of the ITO/SAM substrate. Using the KPM method, which measures the surface potential energy of the films, the energy bands of the ITO were increased to maximum 5.09 eV. The ITO/SAM/P3HT: PCBM film's surface potential was determined to be 0.18 eV after being annealed at 80 °C. The surface potential of the modified films was discovered to be 0.33 V and 0.39 V when the annealing temperature was raised from 80 °C to 120 °C and 160 °C. The maximum device efficiency was demonstrated by the ITO/SAM/P3HT: PCBM film after an hour of annealing at 160 °C.     

KOH activated carbon derived from biomass-banana fibers as an efficient negative electrode in high performance asymmetric supercapacitor

Here we demonstrate the fabrication, electrochemical performance and application of an asymmetric supercapacitor(AS) device constructed with β–Ni(OH)_2/MWCNTs as positive electrode and KOH activated honeycomb-like porous carbon(K-PC) derived from banana fibers as negative electrode. Initially,the electrochemical performance of hydrothermally synthesized β–Ni(OH)_2/MWCNTs nanocomposite and K-PC was studied in a three-electrode system using 1 M KOH. These materials exhibited a specific capacitance(Cs) of 1327 F/g and 324 F/g respectively at a scan rate of 10 m V/s. Further, the AS device i.e.,β–Ni(OH)_2/MWCNTs//K-PC in 1 M KOH solution, demonstrated a Cs of 156 F/g at scan rate of 10 m V/s in a broad cell voltage of 0–2.2 V. The device demonstrated a good rate capability by maintaining a Cs of 59 F/g even at high current density(25 A/g). The device also offered high energy density of 63 Wh/kg with maximum power density of 5.2 kW/kg. The AS device exhibited excellent cycle life with 100% capacitance retention at 5000 th cycle at a high current density of 25 A/g. Two AS devices connected in series were employed for powering a pair of LEDs of different colors and also a mini fan.     

Study on electrochemical performance of activated carbon in aqueous Li2SO4, Na2SO4 and K2SO4 electrolytes

The electrochemical performances of activated carbon (AC) in 0.5 mol/l Li₂SO₄, Na₂SO₄ and K₂SO₄ aqueous electrolytes were investigated. The cyclic voltammetric results at different scan rates show that the rate behaviors of AC in the three electrolytes improve in the order of Li₂SO₄ < Na₂SO₄ < K₂SO₄. This improvement can be mainly ascribed to the following two reasons: (1) the decreasing equivalent series resistance in the order of Li₂SO₄ > Na₂SO₄ > K₂SO₄, which is the main factor influencing the maximum output power, and (2) the increasing migration speed of hydrated ions in the bulk electrolyte and in the inner pores of AC electrode in the order of Li⁺ < Na⁺ < K⁺. Their cycling behaviors do not show any differences in capacitive fading. The above results provide valuable information to explore new hybrid supercapacitors.     

Effect of surface area and heteroatom of porous carbon materials on electrochemical capacitance in aqueous and organic electrolytes

A series of porous carbon materials with wide range of specific surface areas and different heteroatom contents had been prepared using polyaniline as carbon precursor and KOH as an activating agent. Effect of surface area and heteroatom of porous carbon materials on specific capacitance was investigated thoroughly in two typical aqueous KOH and organic 1-butyl-3- methylimidazolium tetrafluoroborate/acetonitirle electrolytes. The different trends of capacitance performance were observed in these two electrolytes. Electrochemical analyses suggested that the presence of faradaic interactions on heteroatom-enriched carbon materials in organic environment is less significant than that observed in aqueous electrolytes. Thus, in aqueous electrolyte, a balance between surface area and heteroatom content of activated porous carbon would be found to develop a supercapacitor with high energy density. In organic electrolyte, the capacitance performance of porous carbon is strongly dependent on the surface area. The results may be useful for the design of porous carbon-based supercapacitor with the desired capacitive performance in aqueous and organic electrolytes.     

Supercapacitive behaviors of the nitrogen-enriched activated mesocarbon microbead in aqueous electrolytes

The activated nitrogen-enriched novel carbons (a-NENCs) have been prepared by direct carbonization of polyaniline/activated mesocarbon microbead composites and further activated by 16 M?HNO₃. The electrochemical performances and supercapacitive behaviors of the a-NENCs in 6 M KOH, 1 M?H₂SO₄, and 0.5 M?K₂SO₄ solutions are evaluated by cyclic voltammetry, galvanostatic charge/discharge, electrochemical impedance spectroscopy, cyclic life, leakage current, and self-discharge measurements. The results demonstrate that the supercapacitors perform definitely supercapacitive behaviors; especially in 6 M KOH electrolyte, the supercapacitor represents much better electrochemical performance with more excellent reversibility, shorter relaxation time of 1.11 s, and nearly ideal polarizability. The maximum specific capacitance of the supercapacitors using a-NENCs as active electrode material is 85.1 F?g^?1 at a rate of 500 mA?g^?1 in 6 M?KOH. These outcomes indicate that the 6 M?KOH aqueous solution is a promising electrolyte for the supercapacitor with a-NENCs as electrode material.     

Preparation of manganese dioxide loaded activated carbon adsorbents and their desulfurization performance

Manganese dioxide loaded activated carbon adsorbents (MnO₂/AC) were prepared and characterized by N₂ adsorption-desorption, BET method, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrometry (FT-IR) and scanning electron microscopy (SEM). Effects of preparation conditions and adsorption conditions on desulfurization performance of the adsorbents were studied in a fixed-bed adsorption apparatus. Experimental results show that the surface area and pore volume of MnO₂/AC decreased compared with the unmodified activated carbon, but the adsorption capacity to H₂S was improved greatly. A suitable H₂S removal activity was obtained with manganese dioxide to activated carbon ratio of 1.1: 1 and the calcination temperature of 250°C. At the adsorption temperature of 40°C and gas flow rate of 20 mL/min, the H₂S saturation capacity and H₂S removal rate reached up to 713.25 mg/g and 89.9%, respectively.     

Global non-ideality effects in adsorption of organic substances from dilute aqueous solutions on activated carbon

Summary A method for the quantitative estimation of the global non-ideality of the adsorption of weak organic electrolytes on activated carbon from dilute aqueous solutions is presented. The method is based on the analysis of aGraham plot which reflects the adsorption isotherm deviations from ideality. Averaging these deviations over the whole range of adsorption, one gets a single value representing the global non-ideality of a system. The method also allows to estimate the contributions of heterogeneity and interactions in the adsorbed phase to the global non-ideality effect. The theoretical considerations are illustrated by some model calculations. The usefulness of the method is tested for experimental data of benzoic and salicyclic acid adsorption over a wide range ofpH and concentrations.

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Globaler Effekt der Nicht-Idealität bei der Adsorption organischer Substanzen aus verdünnten wässerigen Lösungen an Aktivkohle

Zusammenfassung Es wird eine Methode zur quantitativen Abschätzung der globalen Nicht-Idealität für die Adsorption schwacher organischer Elektrolyte aus verdünnten wässerigen Lösungen an Aktivkohle vorgestellt. Diese Methode basiert auf der Analyse der bekanntenGraham-Abhängigkeit, die die Abweichung der Adsorptionsisotherme von der Idealität zeigt. Bei Errechnung des Durchschnittwertes dieser Abweichung über den ganzen Asorptionsbereich erhält man einen Wert, der die globale Nicht-Idealität für ein Adsorptionssystem charakterisiert. Die Methode erlaubt auch, den Beitrag der Heterogenität und der Wechselwirkungen in der Adsorptionsphase zum globalen Effekt der Nicht-Idealität abzuschätzen. Die theoretischen Erörterungen werden an Hand von Modellberechnungen illustriert. Die Nutzbarkeit der Methode wurde mit experimentellen Daten der Benzoe- und Salicylsäureadsorption in einem weiten Bereich vonpH und Konzentration getestet.

     

Highly mesoporous and high surface area carbon: A high capacitance electrode material for EDLCs with various electrolytes

Activated carbon fibers (ACFs) with high surface area and highly mesoporous structure for electrochemical double layer capacitors (EDLCs) have been prepared from polyacrylonitrile fibers by NaOH activation. Their unique microstructural features enable the ACFs to present outstanding high specific capacitance in aqueous, non-aqueous and novel ionic liquid electrolytes, i.e. 371 F g⁻¹ in 6 mol L⁻¹ KOH, 213 F g⁻¹ in 1 mol L⁻¹ LiClO₄/PC and 188 F g⁻¹ in ionic liquid composed of lithium bis(trifluoromethane sulfonyl)imide (LiN(SO₂CF₃)₂, LiTFSI) and 2-oxazolidinone (C₃H₅NO₂, OZO), suggesting that the ACF is a promising electrode material for high performance EDLCs.     

Preparation and electrochemical performance of the layered cobalt oxide (Co3O4) as supercapacitor electrode material

Layered Co₃O₄ composed of oriented self-assembled micrometer-length rectangular 2D flakes has been successfully synthesized by a hydrothermal method in combination with subsequent calcination process. Structural and morphological characterizations were performed using powder X-ray diffraction and field emission scanning electron microscopy. The component and thermal stability of the sample were measured by FT-IR and thermal analyses, including thermogravimetry and differential thermal analysis. The electrochemical performances of the as-prepared Co₃O₄ product were investigated by cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and constant current charge/discharge techniques. The electrochemical results demonstrate that the layered Co₃O₄ product displays good capacitive behavior with a specific capacitance of 263 F?g^?1 within a potential range of ?0.4–0.55 V at a current density of 1 A?g^?1 and a large capacity retention with 89.4 % of the initial capacitance over 1,000 consecutive cycles at 3 A?g^?1, indicating that the as-prepared Co₃O₄ product can be a promising electroactive material for supercapacitor.     

Effect of electrode charge balance on the energy storage performance of hybrid supercapacitor cells based on LiFePO4 as Li-ion battery electrode and activated carbon

Journal of Solid State Electrochemistry - Hybrid supercapacitors using asymmetric, LiFePO4 (LFP) lithium intercalation and electric double layer activated carbon (AC) electrodes combining the high...     

The preparation and performance of flocculent polyaniline/carbon nanotubes composite electrode material for supercapacitors

Polyaniline (PANI)/carbon nanotubes (CNTs) composite electrode material was prepared by in situ chemical polymerization. The structure and morphology of PANI/CNTs composite are characterized by Fourier infrared spectroscopy, scanning electron microscope, and transmission electron microscopy. It has been found that a flocculent PANI was uniformly deposited on the surface of CNTs. The supercapacitive behaviors of the PANI/CNTs composite materials are investigated with cyclic voltammetry, galvanostatic charge/discharge, impedance, and cycle life measurements. The results show that the PANI/CNTs composite electrodes have higher specific capacitances than CNT electrodes and better stability than the conducting polymers. The capacitance of PANI/CNTs composite electrode is as high as 837.6 F g⁻¹ measured by cyclic voltammetry at 1 mV s⁻¹. Besides, the capacitance retention of coin supercapacitors remained 68.0% after 3,000 cycles.     

A novel asymmetric activated carbon electrode doped with metal-organic frameworks for high desalination performance

Journal of Solid State Electrochemistry - In this work, we synthesized metal-organic framework Cu3(BTC)2 which was applied as the doping materials of anode electrodes in capacitive deionization...