Enhancing the performance of activated carbon based scalable supercapacitors by heat treatment (original) (raw)
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Activated carbon for supercapacitor electrodes with an aqueous electrolyte
High Temperature, 2015
Activated carbons on the basis of wood are obtained; the carbons are characterized by the optimal characteristics necessary to apply in supercapacitors with a sulfuric acid based electrolyte. The properties of activated carbon including detailed study of the porous structure by the limited evaporation technique, as well as their electrochemical parameters in the supercapacitor structure, are investigated comprehensively. For material synthesis, correlations between the regime factors, the porous structure, and the functional charac teristics of the supercapacitors on that basis are found. Suppositions concerning the peculiarities of formation of the porous structure of activated carbons obtained by the thermochemical synthesis method with use of an alkali as the activator, as well as the influence of the synthesis parameters on the electrochemical character istics of the supercapacitors, are proposed.
Catalysts
The present work reports the synthesis of biomass derived activated carbon and its electrochemical behaviour in different electrolytes. Ricinus communis shell (RCS) was used as a raw material in this study for the synthesis of activated carbon (AC) following a high-temperature activation procedure using potassium hydroxide as the activating agent. The physical and structural characterization of the prepared Ricinus communis shell-derived activated carbon (RCS-AC) was carried by Brunauer-Emmett-Teller analysis, X-ray diffraction analysis, Fourier Transform Infrared Spectroscopy, Raman Spectroscopy and Scanning Electron Microscopy. The synthesized AC was electrochemically characterized using various techniques such as Cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) tests, and Electrochemical impedance spectroscopy (EIS) measurements in different aqueous electrolytes (KOH, H2SO4, and Na2SO4). The results show that the double layer properties of the RCS-AC material in diff...
Thermochemically activated carbon as an electrode material for supercapacitors
Nanoscale research letters, 2015
The results of electrochemical studies of nanoporous carbon as electrode material for electrochemical capacitors (EC) are presented in this work. Nanoporous carbon material (NCM) was obtained from the raw materials of plant origin by carbonization and subsequent activation in potassium hydroxide. It is established that there is an optimal ratio of 1:1 between content of KOH and carbon material at chemical activation, while the maximum specific capacity of NCM is 180 F/g. An equivalent electrical circuit, which allows modeling of the impedance spectra in the frequency range of 10(-2) to 10(5) Hz, is proposed, and a physical interpretation of each element of the electrical circuit is presented.
2018 7th International Conference on Computer and Communication Engineering (ICCCE), 2018
A simple RC equivalent circuit model often used to represents a supercapacitor. The model is far from accurately model the behavior of the device. A 2cm by 2 cm supercapacitor prototype based on Activated carbon as the active electrode material and NaOH as the electrolyte was fabricated. This prototype was characterized using Cyclic Voltammetry and Galvanostatic Charge Discharge to get the supercapacitor working potential window, capacitance and internal resistance. The device works up to 0.7V with capacitance of up to 1.6F and internal resistance as low as 190 Ohm was found for the prototype. Several equivalent circuit model of a supercapacitor was simulated to produce similar response of the prototype. Multiple Branch Parallel RC circuit response profile fit the experimental profile the best.
Renewable and Sustainable Energy Reviews, 2015
An overview of the recent development in the production of activated carbon electrodes from agricultural waste biomass for application in supercapacitors is presented. The use of agricultural waste biomass as precursor for the production of activated carbons has been on the increase lately because it is cheap, readily available and also viewed as a veritable way of combating waste disposal problem in the agricultural industries. The effects of activating methods (physical, chemical and microwave-induced) and conditions on the properties of activated carbons are reviewed. The survey of articles published in the last decade indicates the viability of biomass active carbons being used as electrodes in supercapacitors. Under optimum process conditions, active carbons with specific capacitance as high as 374 F g À 1 and high-rate long-cycle stability at 4 A g À 1 have been produced. In this review, the influence of surface modification on activated carbon properties is also discussed. From the survey literature, it can be seen that the changes in surface chemistry and the introduction of specific surface functionalities on the surface of activated carbons impacted more on the electrochemical properties than the physiochemical properties of the activated carbons.
Wood-based activated carbons for supercapacitors with organic electrolyte
Holzforschung, 2015
The thermocatalytical synthesis conditions required for the activation of wood charcoal with NaOH in terms of the formation of pores in its structure were investigated. The present study was conducted to explore the potential application of activated carbons as electrodes in supercapacitors with organic electrolyte. The total pore volume and micro- and mesopore ratio were controlled by the activation temperature and alkali addition rate. The working characteristics of carbon electrodes (e.g., specific capacity and ohmic losses) in supercapacitors are strongly influenced by the properties of the pores in their structures. Herein, the optimal ratio of raw material to activator and activation temperature are established: an increase in the ratio of NaOH to carbonizate rate by a factor of 2 and setting the synthesis temperature at 700°C positively influence the electrochemical characteristics of supercapacitors and provide them with specific capacities of up to 160 F g-1.
Journal of Solid State Electrochemistry, 2016
Activated carbon from tree bark (ACB) has been synthesized by a facile and environmentally friendly activation and carbonization process at different temperatures (600, 700, and 800 °C) using potassium hydroxide (KOH) pellets as an activation agent with different mass loading. The physicochemical and microstructural characteristics of the as-obtained material revealed interconnected micro/mesoporous architecture with increasing trend in specific surface area (SSA) as carbonization temperatures rises. The SSA values of up to 1018 m 2 g-1 and a high pore volume of 0.67 cm 3 g-1 were obtained. The potential of the ACB material as suitable supercapacitor electrode was investigated in both a three and two electrode configuration in different neutral aqueous electrolytes. The electrodes exhibited EDLC behaviour in all electrolytes with the Na 2 SO 4 electrolyte working reversibly in both the negative (-0.80 V to-0.20 V) and positive (0.0 V to 0.6 V) operating potentials. A specific capacitance (C S) of up to 191 F g-1 at a current density of 1 A g-1 was obtained for the optimized ACB electrode material in 1 M Na 2 SO 4 electrolyte. A symmetric device fabricated exhibited specific C S of 114 F g-1 at 0.3 A g-1 and excellent stability with a coulombic efficiency of a 100% after 5000 constant charge-discharge cycles at 5.0 A g-1 and a low capacitance loss for a floating time of 70 h.
Effects of thermal treatment of activated carbon on the electrochemical behaviour in supercapacitors
This paper studies the electrochemical behaviour of activated carbons with different oxygen content and investigates the contribution of pseudocapacitance to the global behaviour of the samples. A mesophase-derived activated carbon was further heat treated to 600 or 1000 °C in nitrogen. The changes in texture and surface chemistry induced by the thermal treatment were deeply studied. The electrochemical behaviour of the samples was studied in two- and three-electrode cells. The contribution of pseudocapacitance was evaluated by cyclic voltammetry and by the differences of specific capacitance obtained from galvanostatic tests performed in acidic (H2SO4) and basic (KOH) media. The presence of an extra capacitance due to redox reactions has been proved both in acidic and basic media for the samples with high oxygen content, although its contribution in basic media is significantly lower. The results obtained clearly indicate that the oxygen responsible for CO-evolution participates in...
International Journal of Electrochemical Science
Varying amounts of graphite powder (0 to 20 wt%) are mixed as an additive with self-adhesive carbon grains, which are produced from pre-carbonized powder derived from the fibers of oil palm empty fruit bunches, a by-product from palm oil mills. The mixtures are treated with KOH and converted into green monoliths (GMs). The GMs are carbonized and activated via a multistep heating profile to produce activated carbon monolith (ACM) electrodes. X-ray diffraction, field emission scanning electron microscopy and nitrogen adsorption-desorption isotherm analysis demonstrate that the addition of graphite influences the structure, microstructure and porosity of the ACM electrode materials. Electrochemical impedance spectroscopy, cyclic voltammetry and galvanostatic chargedischarge studies show that the best frequency response of the electrodes is obtained using 4 wt% of graphite. A tremendous decrease in the equivalent series resistance (~70%) and response time (~87%) leads to an improvement of specific power by 39 % and an 8-fold increase in the maximum operating frequency (from ~0.13 Hz to ~1 Hz). Furthermore, the cells incorporating the electrodes with 4 wt% of graphite retain 50% of their capacitance up to 1 Hz. These findings show that the cheap graphite powder can be a useful additive for preparing supercapacitor electrodes from activated carbon.