Activated Carbon Cloth Electrodes Research Articles

High-voltage aqueous supercapacitors enabled by polysiloxane passivation coating-modified carbon cloth electrode

The voltage window plays a crucial role in determining the energy density of supercapacitors. The limited energy density of carbon-based supercapacitors poses a significant challenge to their widespread adoption. Here, we propose a novel approach to modify carbon cloth by implementing a polysiloxane (PSiO) passivation coating. This forms an ion-conductive and electron-insulating thin film on the surface, effectively impeding electron conduction from electrode surface to electrode/electrolyte interface and suppressing electrolyte electrolysis. Consequently, an expanded voltage window is realized, thereby enhancing the energy density of aqueous carbon-based supercapacitors. The carbon cloth electrode modified with the PSiO passivation coating (CC-A-KH560) exhibits exceptional electrochemical performance, with a significantly increased 78.6 % widened applicable potential range compared to the activated carbon cloth electrode (CC-A). In a two-electrode configuration, the voltage window is broadened from 0.8 V for CC-A to 1.4 V for CC-A-KH560, and the energy density based on CC-A-KH560 is 8 times that based on CC-A. The good stability and durability are also obtained for the firm C–O–Si bonds during PSiO modification. More importantly, this design provides a generic solution of PSiO passivation coating-modified carbon electrode, applicable for diversified silicane couple agents, to realize a high-voltage energy storage performance for aqueous supercapacitors.

Nitrogen-doped activated carbon composite electrode for deionization of phosphate removal and DFT model adsorption of phosphates

Phosphate discharge in sewage can result in water eutrophication, posing a threat to aquatic ecosystems. Membrane capacitive deionization (MCDI) has demonstrated outstanding performance and significant potential for salt removal and nutrient recovery. In this study, a nitrogen-doped activated carbon electrode material (NAC) was synthesized through one-step pyrolysis to selectively remove phosphate from MCDI. At a voltage of 1.2V, a flow rate of 20 mL/min, and a pH of 6.51, the phosphate adsorption capacity of the NAC electrode was determined to be 1.60 mg/g. The study revealed that NAC pHpzc increased from 4.14 to 6.44, effectively broadening the pH range for phosphate removal. In the presence of competing ions (NO3−, Cl−, and SO42−) at a concentration of 0.5 M, the electroadsorption capacity of phosphate decreased to 1.21 mg/g, 1.14 mg/g, and 1.02 mg/g, respectively. The kinetic parameters of adsorption indicated that NAC electroadsorbed phosphate through physical adsorption, with the maximum adsorption capacity achieved at 303K. Data from the Freundlich isothermal model suggested that phosphate adsorption by the NAC electrode involves a multilayer adsorption process. A carbon structure model of density functional theory (DFT), incorporating doped nitrogen, was constructed based on XPS analysis. Following nitrogen doping, the electrostatic potential (ESP) of unsaturated carbon atoms became more positive, enhancing the ability of nitrogen-doped activated carbon to adsorb phosphate. This study provides compelling evidence that nitrogen doping facilitates the adsorption of phosphate by carbon materials.

Preparation and environmental impact assessment of NI-N modified sludge activated carbon electrode materials

With the activated sludge in urban sewage treatment as the precursor material, the carbon material is prepared by high temperature carbonization, and then the nickel-nitrogen modified activated carbon material is prepared by potassium hydroxide activation, urea and nickel doping. Electrochemical experiments with activated carbon materials show that it has a good specific capacitance of 345.9 F/g at 1 A/g current density. After 2 000 cycles at a current density of 10 A/g, it still maintains 84.53% capacitance, shows found that the main source of influence is the power consumption in the process of sludge carbonization.

Capacitive deionization: Capacitor and battery materials, applications and future prospects

Water scarcity all over the world attracts alternative methods to purify saline water and supplement the available dwindling freshwater resources. Capacitive deionization (CDI) is hopeful to supply water to the population due to operation at low potential along with low energy expenditure when low salinity (5 mM NaCl) feed water solutions are desalinated. Electrode material is the main controlling factor in CDI system and a lot of efforts are devoted to develop excellent materials for better CDI performance. So far, carbon materials are widely used as the electrode for CDI, though limitations such as co-ion expulsion and faradaic reactions hinder their full utilization. Alternatively, battery materials are used since their performance is great due to mitigation of co-ions ejection as well as faradaic reactions. In 2019 our group reviewed factors affecting the performance of activated carbon electrode materials and revealed lack of selectivity, co-ion expulsion, low electrical conductivity and inappropriate pore size distribution to largely contribute to its low salt removal capacity [1]. Therefore, herein, we extend the discussion beyond AC to include other carbons such as aerogels, nanotubes, graphenes etc., and battery materials such as MXenes, sodium super ionic conductors, and BiOCl to mention the few. This article also discusses the extent CDI is applied in the laboratory scale as well as in the field for desalination of real water, wastewater remediation and removal of harmful contaminants to substantiate what it can offer beyond the laboratory experiments. The work is expected to save as a complete reference for the progress of CDI electrode materials and its applications in water purification.

Uncharged Monolithic Carbon Fibers Are More Sensitive to Cross-Junction Compression than Charged.

Textile-based wearable robotics increasingly integrates sensing and energy materials to enhance functionality, particularly in physiological monitoring, demanding higher-performing and abundant robotic textiles. Among the alternatives, activated carbon cloth stands out due to its monolithic nature and high specific surface area, enabling uninterrupted electron transfer and energy storage capability in the electrical double layer, respectively. Yet, the potential of monolithic activated carbon cloth electrodes (MACCEs) in wearables still needs to be explored, particularly in sensing and energy storage. MACCE conductance increased by 29% when saturated with Na2SO4 aqueous electrolyte and charged from 0 to 0.375 V. MACCE was validated for measuring pressure up to 28 kPa at all assessed charge levels. Electrode sensitivity to compression decreased by 30% at the highest potential due to repulsive forces between like charges in electrical double layers at the MACCE surface, counteracting compression. MACCE's controllable sensitivity decrease can be beneficial for garments in avoiding irrelevant signals and focusing on essential health changes. A MACCE charge-dependent sensitivity provides a method for assessing local electrode charge. Our study highlights controlled charging and electrolyte interactions in MACCE for multifunctional roles, including energy transmission and pressure detection, in smart wearables.

Preparation of Manganese Oxide/Bamboo Activated Carbon Electrode Materials with Excellent Electrochemical Performance

Preparation of Manganese Oxide/Bamboo Activated Carbon Electrode Materials with Excellent Electrochemical Performance

Activated carbon cloth electrodes for capacitive deionization: a neutron imaging study

Neutron imaging was employed to track the uptake of Gd3+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{3+}$$\\end{document} ions by the sub 2 nm micropores of charged activated carbon cloth electrodes from an aqueous Gd(NO3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document})3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document} solution. The transmitted neutron intensity evinces the persistent presence of Gd3+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{3+}$$\\end{document} in the micropores during the discharge cycle, which is caused by the adsorption of oppositely charged ions. The charge efficiency of the activated carbon cloth system was determined by direct comparison with the imaged Gd3+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{3+}$$\\end{document} concentration changes, with which the influence of ion swapping and resistive losses on capacitive deionization cells can be ascertained.

The optimal micro- and meso-pores oriented development of Eucommia ulmoides oliver wood derived activated carbons for capacitive performance

The optimization of pore characteristics is of pivotal importance for enhancing the capacitive performance of activated carbons (ACs) in supercapacitor applications. This study delved into the impact of porous structures, developed through varying activation temperatures (350–850 ֩C), on capacitive performance of wood derived activated carbons (ACs). Our findings revealed that AC350, possessing the highest micropore surface area (Smicro) of 903.38 m2 g-1 and a micropore volume (Vmicro) of 0.43 cm3g-1, exhibited the lowest specific capacitance (SC) of 13 Fg-1. This suggests that a higher SC is not significantly associated with a greater quantity of micropores. Conversely, AC850, with a peak Smeso of 1472.89 m2 g-1 and Vmeso of 1.24 cm3g-1, demonstrate a SC of only 83 Fg-1, indicating that the higher SC is not significantly correlated with an increased amount of mesopores either. However, AC650 displayed an optimal SC of 123 Fg-1, with an ideal Smeso/Smicro ratio of 2.16 and Vmeso/Vmicro ratio of 5.50. This underscores that the superior capacitive performance of ACs based electrode materials is intricately linked to an effective amalgamation of micro- and meso-pores. By strategically manipulating the pore composite structure to augment the charge storage capability of activated carbon electrode materials, we can enhance the energy density of capacitors. This advancement is poised to further propel the application of biomass-derived activated carbon and its composite capacitor technology in energy storage domains.

Binder-free MoSe/MMSe composite and onion-derived activated carbon electrode materials for high-performance hybrid supercapacitors

MoSe/MMSe composite electrode materials were prepared on Ni foam via a facile hydrothermal technique. The composite electrode showed superior electrochemical performanc with ultra-long cycling stability.

Electrochemical Analysis and Quantification of Anodic Oxidation on Activated Carbon Cloth Electrodes through Cyclic Voltammetry

Capacitive Deionization (CDI) has applications ranging from water purification to biofuels processing. For CDI to be a viable scalable technology, electrode stability is critical. In extended experiments the activated carbon cloth (ACC), used for the electrode, has been previously observed to degrade as a result of surface oxidation reactions. Carbon cloth oxidation can reduce the surface area and alter the pore structure, in turn reducing the adsorption capacity. While the behavior of oxidation is known, a reliable method of quantifying the extent of degradation is lacking. To quantify it, cyclic voltammetry was explored to measure the capacitance of pristine and oxidized carbon cloth samples. A three-electrode electrochemical cell was used to quantify capacitance of activated carbon cloth in 1M NaCl solution. The specific capacitance of carbon cloth that underwent anodic oxidation was lower than cathodic and pristine carbon cloth. Further tests analyzed the change in the severity of the anodic degradation on whether the initial CDI separations were performed on organic or inorganic ions. Scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) was utilized to verify and quantify surface oxidation. Cyclic voltammetry is demonstrated as a simple and reliable method for analyzing and quantifying anodic oxidation on activated carbon cloth electrodes in CDI stacks.

Bio-inspired electrode materials from Prosopis Juliflora Wood provide 2.2 V with KOH/water/DMF/PVA electrolyte for supercapacitor applications

Highly porous carbon material was prepared from Prosopis Juliflora Wood by a simple chemical activation method for different ratios of carbon/KOH at the carbonization temperature of 800°C. The synthesized carbon was investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR), RAMAN and high-resolution scanning electron microscope (HR-SEM) that ascertain the existence of highly porous activated carbon. High-resolution transmission electron microscope (HRTEM) images clearly show the porous structure. Electrochemical properties of synthesized Activated carbon electrode material were measured with 3 M KOH/Water/DMF electrolyte in three-electrode system. It shows a superior specific capacitance and cyclic stability of 98% up to 5000 cycles. Asymmetric supercapacitor was assembled with V-5 sample and Graphite as positive and negative electrode materials, respectively, using KOH/Water/DMF/PVA as Electrolyte. The fabricated device displays a high energy density of 61.54 W h kg−1 with a power density of 3500 W kg−1 accompanied by good cyclic stability of 92% of capacitance retention over 5000 charge–discharge cycles. This work proides a convenient method to prepare the high value added electrode materials for future wearable and portable electronic devices.

Fabrication and utilization of ternary cubical nanostructure modified activated carbon cloth electrodes for capacitive deionization system

Cubical nanostructure zinc tin oxide (ZTO) was in-situ deposited on activated carbon cloth (ACC) substrate via a co-precipitation method. The amount and size of ZTO on the ACC substrate were varied by changing the different overall metal ion (Sn4+ and Zn2+) concentrations. The surface morphology and crystalline analysis revealed the well distributed cubic shape perovskite ZTO on the ACC substrates. The ZTO-deposited ACC electrodes showed superior electrochemical performances with higher specific capacitance and better ion transfer activity than pristine ACC. ZTO deposited ACC substrates were used as electrodes in a capacitive deionization system. ACC substrate coated with 0.01 M Sn and Zn metal concentrations achieved the best desalination efficiency of 52%, salt adsorption capacity of 45.0 ± 2 mg/g and faster salt adsorption rate of 0.14 mg/g/s compared to the other tested electrodes using 500 ppm NaCl solution. Further desalination of real groundwater (1000 ppm) achieved with ions adsorption improvement of 36% for Na+, 48% for Ca2+, 60% for Mg2+, and 46% for Cl- compared to the pristine ACC. Additionally, compared to the pristine ACC, the ZTO-coated electrode enhanced the ions adsorption rate and reduced energy consumption by 40%. Post surface characterization of used pristine ACC displayed substantial scaling of the minerals from the ground water but ZTO-II electrodes exhibited better stability with less scaling. The outcomes of this study provide a stepping stone for the modification and utilization of electrodes for the real brackish water in the CDI system.

Flexible self-support carbon-based material with N[sbnd]F doping and Co embedding for supercapacitors

A flexible porous self-support activated carbon electrode material with NF doping and Co embedding is obtained (ACC@PVDF0.1) by a simple pyrolysis method at a relatively low temperature (600 °C). The multifunctional interface is prepared from polyvinylidene fluoride (PVDF) powder as the carbon and fluorine sources, ZIF-67 as the nitrogen source. After a simple physical covering on an activated carbon cloth (CC), pyrolysis under nitrogen gas environment, the porous self-support activated carbon electrode material with N, F doping and Co embedding can be obtained. The obtained carbon-based material has merits of high specific area (399.8 m2 g−1), high wettability and conductivity because of the N and F doping. The prepared carbon material displays a specific areal capacitance of 0.717 F cm−2 at the current density of 1 mA cm−2 in 1 M Na2SO4, and the capacitance retention remains 92.7 % after 10,000 charge-discharge cycles. An asymmetric supercapacitor (ASC) based on the substrate material of ACC@PVDF0.1 is assembled with the MnO2/AC@PVDF as the positive electrode and the Mxene/AC@PVDF as the negative electrode. It can be operated in a 0–1.8 V voltage window, and demonstrates a specific capacitance of 0.415 F cm−2 in 1 M Na2SO4 at the current density of 1 mA cm−2. The power density is 11.24 mW cm−3 at the energy density of 2.33 mWh cm−3, which shows that the prepared activated carbon material may be a promising candidate for flexible self-support supercapacitors in future.

Application of long fibrous coconut silk-based porous carbon in flexible supercapacitor

All-solid-state flexible supercapacitors are considered to be one of the ideal candidates for energy storage in the next generation of wearable electronic devices due to their high capacitance performance and excellent mechanical flexibility. Biomass-based carbon materials are regarded as the ideal precursors for carbon-based electrode materials due to their wide sources, low cost, natural and abundant biological features. In this work, long-fiber coconut silk with vascular bundle structure was selected as the precursor, the controllable adjustment of the pore structure and conductive characteristics of the electrode material was achieved by changing the KOH activation temperature. The specific surface area of the activated carbon electrode material etched with KOH at 900 °C can reach 2794 m2·g−1. The high specific surface area and reasonable pore size distribution provide abundant active sites for the adsorption of electrolyte ions, which leads to the excellent electrode specific capacitance (2 mV·s−1，634 F·g−1，10.73 Wh·kg−1) of the symmetric flexible supercapacitor combined with PVA (polyvinyl alcohol)/H2SO4 gel electrolyte. At the same time, the long-fiber carbon skeleton has intrinsically high Young's modulus, which enables the flexible all-solid-state supercapacitor to maintain better electrochemical stability and mechanical durability under mechanical deformation, and it's retention rate can reach 101.5 % after 10,000 bending experiments at an inner angle of 140°. It proves the great advantages and potential of coconut silk-based biomass carbon materials in the field of preparing flexible supercapacitors, and promotes the development of energy storage units for next-generation wearable electronic devices.

Design of three-dimensional hexagonal petal-like nickel-copper cobaltite // luffa sponge-derived activated carbon electrode materials for high-performance solid-state supercapattery

Three-dimensional porous nanostructured materials are considered superior materials for energy storage applications due to their high storage capability. A nickel copper-cobalt oxide (NCC) composite with a uniform 3-D porous nanostructure (positive electrode materials) and luffa sponge-derived activated carbon (LPAC) with honeycomb-like structure (negative electrode materials) were synthesized by a simple hydrothermal and chemical method. A sample of the nickel-copper cobalt oxide-5 (NCC-5) nanocomposite reached a high specific capacitance of 1048 F/g at the current density of 0.5 A/g. The NCC-5 nanocomposite sample shows a retention capacity of 93 % after 10,000 charge and discharge cycles with 95 % of Coulombic efficiency (CE). The LPAC illustrates a remarkable specific capacitance of 909 F/g at 1 A/g of current density, compared to the best literature value of 400 F/g. The full-cell NCC-5//LPAC delivered an energy density of 65 Wh/kg, corresponding to a power density of 500 W/kg. The supercapacitor devices connected in series could glow 55 red LEDs for 5 min.

Recycling Used-Coffee Grounds into Hierarchical Nanostructured Carbon for Supercapacitor Application

Hierarchical nanostructured activated carbon electrode material was prepared from the used-coffee grounds to fabricate a cost-effective, scalable and high-performance symmetric supercapacitor. The interconnected, disordered and microporous material was synthesized in a simple two-stage method of chemical activation with zinc chloride followed by direct pyrolysis of the coffee grounds at 900 ºC in nitrogen atmosphere. The N2 adsorption and desorption analysis showed that the prepared material had an extraordinary surface area of ~1178 m2 g-1. The fabricated symmetric supercapacitor device in non-aqueous tetraethylammonium tetrafluoroborate (TEABF4) electrolyte exhibited 2.7 V cell voltage with superior specific capacitance, energy and power density of 129 F g–1, 56.4 Wh kg–1 and 797.9 W kg–1, respectively. Besides, it also had a high specific capacitance retention of 99% even after 10,000 cycles. This work demonstrated an effective approach to transform coffee grounds into high performance electrode material for renewable energy devices. The observed electrochemical performance evidently showed that the materials derived from waste coffee grounds could be recycled into potential electrode material for supercapacitors. The cost-effectiveness and abundance of waste coffee grounds combined with the simple activation process and high performance of the synthesized material increased its feasibility for commercial applications in energy storage devices.

Effect of activated carbon electrode material characteristics on hardness control performance of membrane capacitive deionization.

Capacitive deionization (CDI) is an electrochemical-based water treatment technology that has attracted attention as an effective hardness-control process. However, few systematic studies have reported the criteria for the selection of suitable electrode materials for membrane capacitive deionization (MCDI) to control hardness. In this study, the effect of electrode material characteristics on the MCDI performance for hardness control was quantitatively analyzed. The results showed that the deionization capacity and the deionization rate were affected by the specific capacitance and BET-specific surface area of the activated carbon electrode. In addition, the deionization rate also showed significant relationship with the BET specific surface area. Furthermore, it was observed that the deionization capacity and the deionization rate have a highly significant relationship with the BET specific surface area divided by the wettability performance expressed as the minimum wetting rate (MWR). These findings highlighted that the electrode material should have a large surface area and good wettability to increase the deionization capacity and the deionization rate of MCDI for hardness control. The results of this study are expected to provide effective criteria for selecting MCDI electrode materials aiming hardness control.

Few-Layer Graphene As an Electrode, Electrode Additive and an Interfacial Layer in Aqueous Supercapacitors

The intermittent nature of many renewable energy sources such as wind and solar, coupled with fluctuations in energy demand, creates a pressing need for efficient, low-cost energy storage technologies. Supercapacitors are promising candidates to play a role in next-generation energy storage systems. They have a higher power density and better cycle life (although lower energy density) than batteries making them ideal for rapid energy storage and deployment [1]. Activated carbon is a favoured electrode material due to high surface area, although low conductivity requires use of a conductive additive (often carbon black), reducing available surface area for charge storage. In contrast, the high conductivity and specific surface area of graphene has made it a promising material for electrochemical double layer supercapacitors (EDLCs) [2], however, performance is limited by restacking of the graphene sheets, reducing available surface area.In this work, high-shear exfoliated few layer graphene (FLG) [3] is investigated both as an electrode material and as a conductive additive/interfacial layer for EDLCs. FLG suspensions were produced under a variety of exfoliation conditions, with platelet thickness and linear dimension determined from Raman spectroscopy based on metrics developed by Backes et al. [4] and through scanning electron microscopy (SEM).The FLG suspensions were used in three ways: i) to create thin ‘graphene paper’ electrodes; ii) as a conductive additive, mixed into the activated carbon electrode material; iii) deposited onto the back of (and diffused within) activated carbon electrodes. These electrodes were investigated by Raman spectroscopy and Scanning Electron Microscopy, before being assembled into symmetric two-terminal aqueous cells then evaluated by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS), and their electrochemical performance related to structure and composition.As expected, pure FLG electrodes often showed excellent low series resistance values, however specific capacitance was low, due to restacking. Directly mixing 5% FLG into activated carbon as a conventional conductive additive led to a specific capacitance of 63 F/g (from CV at 10 mV/s), and a series resistance of 19 W (from GCD at 1 A/g) - markedly inferior to those with 5% carbon black as a conductive additive (95 F/g and 2 Ohm) and inferior even to electrodes with no conductive additive (87 F/g and 10 Ohm).However, post fabrication deposition/infusion of FLG offers comparable performance to carbon black (90 F/g and 1 Ohm) at 7% FLG by weight. As the quantity of FLG is increased the specific capacitance decreases sharply. This behaviour is attributed to FLG restacking on the rear of the electrode, so adding mass whilst providing limited additional capacitance, and compression of the electrode.Adding high-shear exfoliated FLG to activated carbon electrodes shows promise for obtaining the benefits of both materials. At present, FLG/activated carbon electrodes can match the performance of those produced from activated carbon with a carbon black conductive additive and, with further optimization, we expect will be able to exceed them.Figure: a) Cross sectional SEM image of activated carbon electrode with graphene interfacial layer; b) magnified cross sectional SEM image of graphene interfacial layer; c) cyclic voltammograms at 10 mV/s of the different electrodes mentioned in the abstract.

Triethylammonium thiocyanate ionic liquid electrolyte-based supercapacitor fabricated using coconut shell-derived electronically conducting activated charcoal electrode material

Organic solvents are commonly used as commercial electrolytes in supercapacitors, but they have several drawbacks, such as high volatility, toxicity, and environmental issues. To overcome these problems, ionic liquids are used though their high costs hamper commercial applications. In this study, a novel and low-cost ionic liquid based on triethylammonium cation and thiocyanate anion were synthesized and used as the electrolyte in a low-cost supercapacitor fabricated using electronically conducting activated carbon derived from cleaned coconut shells as electrode material. The temperature dependence of electrolyte conductivity was investigated, in the frequency range of 1 Hz-500 kHz, using AC impedance analysis, in the temperature range from 30 °C - 90 °C in ten-degree increments and found to be in the range of 4.5 to 14.4 mS cm−1. The ion transport kinetics behaves according to the Vogel-Tammann-Fulcher (VTF) model with an activation energy (Ea) and the pre-exponential factor (AσT) of 0.0158 eV and 114.9 S m−1 K1/2, respectively. The activated carbon material developed has a high porosity and high electronic conductivity. The electrode fabrication methodology was optimized by varying the polyvinylpyrrolidone (PVP) binder amount with respect to the mass of activated carbon on a titanium sheet as a function of heat treatment temperature. The supercapacitor that gives the highest specific capacitance is based on the electrode constructed using 5 % w/w PVP in 0.50 g of activated carbon deposited on a titanium sheet by heat treating at 200 °C for 20 min. At the scan rate of 5 mV s−1, two-electrode CV studies revealed a specific capacitance of 36.8 F g−1 for the optimized supercapacitor assembly. The electrolyte triethylammonium thiocyanate (TAT) demonstrated good electrochemical stability and a large operating voltage window of 1.8 V and high stability, with 94.4 % capacity retention after 1000 cycles. The AC impedance studies also gave comparable results. Prime novelty statementThe manuscript describes a method to prepare a novel and low-cost ionic liquid material triethylammoniumthiocyanate starting from triethylamine and ammonium thiocyanate, and its application as the ionic liquid electrolyte in a low-cost supercapacitor. The electrode material used in the supercapacitor was fabricated using electronically conducting activated carbon derived from cleaned coconut shells, which were deposited firmly adhering to titanium sheets using polyvinylpyrrolidone binder under optimized heat treatment conditions. As such, both the ionic liquid electrolyte and the activated carbon electrode material are novel and attractive materials for the commercial production of low-cost supercapacitors.

Self-discharge of a supercapacitor with electrodes based on activated carbon cloth

• Self-discharge of a supercapacitor with activated carbon cloth electrodes was investigated. • The dependence of the self-discharge rate on voltage has a minimum. • An equivalent electric circuit of a supercapacitor has been developed from impedance measurements. A study of the self-discharge of supercapacitor (SC) with electrodes based on the activated carbon (AC) cloth CH 900 of the Kuraray Company with an aqueous electrolyte of 1 M MgSO 4 was conducted. The elemental composition of the positive and negative electrodes after electrochemical treatment up to 1.6 V began to radically differ from each other. A very high concentration of hydrogen and oxygen appeared on the positive electrode, which is explained by the formation of functional surface groups (FSG). It was found that the logarithm of the self-discharge rate after 70 min is proportional to the charging voltage. Self-discharge rate dependences on the charge voltage after 1000 and 2000 min have its minimums. These minimums is explained by the action of two oppositely directed mechanisms. First, the pseudocapacity of Faraday redox reactions of FSG makes a significant contribution to the capacity, and second, the very presence of these groups increases the self-discharge rate. At low voltages, the first factor dominates, and at high voltages, the second factor. Based on impedance measurements for small self-discharge times, an equivalent electric circuit of the SC cell has been developed. It is shown that the resistance of the leakage current decreases with voltage increasing, which corresponds with measurements of the self-discharge rate. It is also shown that the self-discharge rate of the SC after 2000 charge–discharge cycles is lower than that corresponding to the initial state of the cell, which is explained by the presence of the FSG.