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e (a) Schematic design of AC/AC symmetric supercapacitor cell, (b) CV curves in different potential windows at 50 mV s ¡1 , (c) CV curves at various scan rates, (d) GCD curves at various specific currents, (e) C sp at different specific current from 3.8 to 5.7 Ag -1 , (f) Nyquist plots of the AC/AC symmetric supercapacitor cell (g) Ragone plot of the AC/AC symmetric supercapacitor cell (h) cycling stability test for AC/AC symmetric supercapacitor cell at 7 A g ¡1 .
Source publication
Halogenated Bromide (Br -) was subsequently dosed to aqueous electrolyte solution to enforce the capacitance features of activated carbon (AC) electrodes in electric double-layer supercapacitor devices for electrical energy storage. Physicochemical properties for AC with sodium sulfate (Na2SO4) and KBr redox additive were assessed by different char...
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... capacitance C sp is 46 F g À1 , and after 1000 GCD cycles, the specific capacitance rises to 80 F g À1 . This improvement is due to the removal of oxygen functional groups [1]. The AC electrode studied in mixed Na 2 SO 4 @KBr electrolytes has excellent retention of 174% of the initial capacitance after 1000 cycles as indicated in Fig. 8b. Fig. 9a gives a schematic representation structure of AC/AC symmetric supercapacitor cell that was assembled by two same sized activated carbon electrodes with a similar mass of 7 mg on 4 cm 2 exposed area, and a piece of tissue paper was used as a separator, and a Na 2 SO 4 @KBr aqueous solution as electrolyte [48,49]. Fig. 9b displays CV ...
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... as indicated in Fig. 8b. Fig. 9a gives a schematic representation structure of AC/AC symmetric supercapacitor cell that was assembled by two same sized activated carbon electrodes with a similar mass of 7 mg on 4 cm 2 exposed area, and a piece of tissue paper was used as a separator, and a Na 2 SO 4 @KBr aqueous solution as electrolyte [48,49]. Fig. 9b displays CV curves for AC/AC symmetric supercapacitor cell at 50 mV s À1 scan rate in variation voltage window from 0 to 1.0 to 0e3 V [3,50,51]. The curves display capacitive performance with a distortion-free quasierectangular curve and are preserved even with a voltage increase of up to 3V. Fig. 9c illustrates CV curves of the AC/AC ...
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... @KBr aqueous solution as electrolyte [48,49]. Fig. 9b displays CV curves for AC/AC symmetric supercapacitor cell at 50 mV s À1 scan rate in variation voltage window from 0 to 1.0 to 0e3 V [3,50,51]. The curves display capacitive performance with a distortion-free quasierectangular curve and are preserved even with a voltage increase of up to 3V. Fig. 9c illustrates CV curves of the AC/AC symmetric supercapacitor cell at various scan rates (10e100 mV s À1 ) in the range from 0 to 3 V, demonstrating the behavior of a double-layer electrical capacitor (EDLC) with a nearly rectangular CV shape. With an increase in the scan rate, the CV curve shape changes hardly, which confirms the good ...
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... V, demonstrating the behavior of a double-layer electrical capacitor (EDLC) with a nearly rectangular CV shape. With an increase in the scan rate, the CV curve shape changes hardly, which confirms the good reversibility and high-speed capabilities of the AC/AC symmetric supercapacitor cell manufactured with good operating cell voltage [6,49e54]. Fig. 9d .5 and 5.7 A g À1 , respectively, which represent admirable peak rates [54]. As indicated in Fig. 9f, the Nyquist plot of symmetrical AC/AC supercapacitor cell shows that the values of the equivalent series resistance (R ESR ) at the initial intercept of the semicircle at the beginning with the real impedance axis of the high frequency ...
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... CV shape. With an increase in the scan rate, the CV curve shape changes hardly, which confirms the good reversibility and high-speed capabilities of the AC/AC symmetric supercapacitor cell manufactured with good operating cell voltage [6,49e54]. Fig. 9d .5 and 5.7 A g À1 , respectively, which represent admirable peak rates [54]. As indicated in Fig. 9f, the Nyquist plot of symmetrical AC/AC supercapacitor cell shows that the values of the equivalent series resistance (R ESR ) at the initial intercept of the semicircle at the beginning with the real impedance axis of the high frequency are 1.2, 2.6, 3.4, and 3.8 U at frequency ranges of 0.01e10 5 Hz, 0.01e10 6 Hz, 0.1e10 5 Hz, and ...
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... range, and also R ct values obtained from the diameter of the semicircle are 9.2, 11.8, 13.2, and 14 U for the frequency ranges 0.01e10 5 Hz, 0.01e10 6 Hz, 0.1e10 5 Hz, and 0.1e10 6 Hz, respectively. Specific energy and specific power are the main metrics that determine the performance of supercapacitor devices in practical applications. Fig. 9g illustrates Ragone's plot, which shows the relationship between symmetrical AC/AC supercapacitor cell's specific energy and specific power with different specific currents. The AC/AC symmetric supercapacitor cell at a specific current of 3.8 A g À1 can deliver superior specific energy of 57.15 Wh kg À1 at a specific power of 5262 W kg ...
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... energy keeps 37 Wh kg À1 even when the specific power reaches 8880 W kg À1 at a specific current of 5.7 A g À1 . Table 3 illustrates the electrochemical performance of Symmetric Supercapacitor cells based on Activated carbon. The cyclic stability of the AC/AC symmetric supercapacitor cell was tested at 7 A g À1 specific currents. As shown in Fig. 9h, the AC/AC symmetric supercapacitor cell shows good cyclic stability with capacitance retention of about 82.8% after 10,000 ...
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Citations
... When a lower scan rate was applied, the ion diffusion became slower; thus, the interaction between electrodes and electrolytes could be maximized. Also, the high-concentration electrolyte provides a higher number of ions, and when measured at a lower scan rate, the electrolyte ions have sufficient time to penetrate electrode pores and finally yield a better electrical charge storage for a good capacitance value [34]. Combining MXene and MoS2 helped in increasing the active area, thus improving the charge-discharge process. ...
Two-dimensional (2D) materials, inclusive of molybdenum disulfide (MoS2), are auspicious due to their structure providing absorption sites and shorter diffusion paths. However, their sheet restacking affects the functional properties, resulting in the device’s low efficiency. A strategy is proposed to combine MoS2 with MXene material. X-ray Diffraction data revealed peaks at d-spacings of 6.07, 2.72, 2.49, 2.27, 1.82, and 1.53 Å. X-ray photoelectron spectroscopy shows prominent peaks for C 1s and Ti 2p, with no signal for Al detected in the pristine Ti3C2 MXene. This indicates successful etching of the Al layer. Electron Microscopes were used to confirm the samples’ morphology and showed that the hybrid sample has a layered flake-like structure with a small sphere attached to the surface. While the HR-TEM confirmed the layered structure of Ti3C2 after exfoliation from Ti3AlC2, consistent with prior studies. Prior, the electrochemical performances of the MXene/MoS2 supercapacitor in 6M KOH aqueous electrolyte were examined through cyclic voltammetry and galvanostatic charge–discharge. The highest specific capacitance reached was 139.71 Fg-1, attributed to heterostructures of an equally distributed MoS2 and MXene. Furthermore, the device retained about 83% of its initial capacitance after 10,000 cycles of cyclic stability testing. The results demonstrated that the MXene material improved the capacitive performance of MoS2, and conversely. Further enhancements can be expected as a result of a major omission in electrode synthesis, particularly the importance of delamination in MXene preparation.
... The samples consist of a well-defined grain microstructure. Upon closer examination at high magnifications, the presence of distinct pores becomes evident in the image 23 . The material was found to possess a loose and porous structure, with interconnected elements held together by numerous pores. ...
In this work, pseudo-stem of a banana plant was used as a sustainable and affordable source to prepare porous carbon materials (PCM) on a large scale. After fine treatment, the material was annealed at 500, 600, and 700 °C using a tube furnace under nitrogen flow. The prepared materials were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelec-tron spectroscopy (XPS). FT-IR spectra show that the broad peak at the range of 1110-1160 cm-1 comes from the superimposed peaks of C-N for a single or more than one functional group which debunks the possibility of generating nitrogen-doped carbon. TEM and SEM analyses confirmed the porous structure of PCM with the pores connected to one, and a spongy structure was observed in the prepared carbon material. XRD analysis revealed that the carbon materials are crystalline. XPS investigation provided information regarding the dimension of which elements are present in the valence states and constituent elements, depicting the presence of a dominant graphitic C1speak at approximately 284 eV, along with a distinct O1s peak at around 532 eV. Additionally, a relatively weaker N1s peak (approximately 400 eV) was observed.
... EDLCs store energy via electrolyte ion accumulation at the nanomaterial interface electrostatically, whereas pseudocapacitors involve faradaic redox reactions on electrode/electrolyte interface, which only have electron-transfer without chemical reactions [1]. Carbon materials such as graphite [4], activated carbon [6], graphene [7], carbon nanotubes [8], and carbon aerogels [9] have been widely used as supercapacitor electrode materials, but they have limitations such as being unsustainable, costly, and having a high carbon footprint [10]. Biochar, is a carbonaceous solid product of biomass pyrolysis, recognised as a carbon-negative technology due to its ability to sequester carbon in different applications for hundreds to thousands of years, thereby effectively removing CO 2 from the atmosphere [11][12][13][14]. ...
... In addition, the specific resistance of aqueous electrolytes is at least 20× less than that of organic electrolytes, which results in a high specific power of SCs using aqueous electrolytes. 34 The field of electrolytes has seen a shift toward using redox additives as mediators to improve the capacitive performance of SC devices. 35 Of the two options, redox additive-based aqueous electrolytes are much easier to handle than organic-additive electrolytes. ...
... 36 A recent exciting strategy has been studied to introduce redox additives-based electrolyte (mediators) into the electrolyte, which significantly improves the capacitance through the redox reaction that occurs in the electrolyte/electrode. For instance, Frackowiak and colleagues 37 34 utilized a potassium bromide (KBr) redox additive electrolyte added to Na 2 SO 4 and achieved a C s of 127 F g −1 with an E d of 57.15 Wh kg −1 . This idea has inspired us to use the addition of a redox additive to an aqueous electrolyte to enhance the performance of SC devices. ...
... The output of the GCD is chronopotentiometry (E vs. time), whereby the electrode's potential output is plotted against time while applying a constant specific current. 34 From Fig. 7a-c, the ACLF-14 performed much better than the ACLF-8 and was significantly better than the ACLF-20. All the ACLF samples exhibit nearly same patterns within the different potential window ranges. ...
BACKGROUND
The capacitive behavior of a supercapacitor (SC) based on activated carbon derived from biomass is enhanced when a halogenated iodide (in this case, iodide, Iˉ) is added to the acidic aqueous electrolyte. In this work, we prepared ultrahigh capacitive performance of O and Mg self‐dual‐doped activated carbon (AC) from Ananas comosus leaf fiber (ACLF) via chemical activation at high temperature, followed by activation under the protection of CO2 to produce commercially feasible electrodes for commercial‐scale SC devices. The prepared ACLFs were characterized through SEM–EDX, XRD, adsorption/desorption of N2. Moreover, in a 2‐electrode setup, the capacitive activity of the prepared ACLFs were evaluated using cyclic voltammetry and galvanostatic charge/discharge techniques in a redox additive electrolyte (1 M H2SO4 + 0.05 M KI).
RESULT
The pairs 3Iˉ/I3ˉ, 2Iˉ/I2, 2I3ˉ/3I2, and I2/IO3ˉ generate reduction–oxidation (redox) peaks in the CV curves and a significant Faradaic plateau in the GCD curves. The ACLF samples delivered an outstanding gravimetric capacitance and energy density as high as 581 F g⁻¹ and 80.69 Wh kg⁻¹ at a power density of 346.14 W kg⁻¹, respectively.
CONCLUSION
The enhanced capacitive activity is a result of the Faradaic pseudocapacitance associated with the redox‐active ions present in the acidic electrolyte solution. This work describes a facile and economical approach to acquiring a potential candidate of electrode materials for SC devices with exceptional performance, achieved via a redox additive‐based electrolyte system. © 2023 Society of Chemical Industry (SCI).
... From GCD analysis, the energy density and power density of all electroactive materials can be calculated using Eq. (2) dan (3) (Maher et al., 2021). (2) = × 3600 ...
The reduced graphene oxide (rGO) and metal (Cu,Zn)-oxide composites were prepared using a one-step hydrothermal technique. The role of (Cu,Zn)-oxide on the physical and electrochemical properties of the composite was investigated. The composite consists of various shapes of ZnO nanoflowers and micro-spheres, as well as Cu-oxide nanoflakes and octahedron-like shapes. The (Cu,Zn)-oxides were formed in between the rGO layers and observed in the rGO-ZnO, rGO-CuO, and rGO-CuO-ZnO composites. The presence of ZnO, CuO, and rGO within the composite structure is also confirmed by the analyses of crystal structure, microstructure, and surface functional groups. Some excess impurities remaining from the surfactant give considerable differences in the electrochemical performance of the composites. The specific capacitance values of the rGO, rGO-ZnO, rGO-CuO, rGO-(0.5CuO-0.5ZnO), and rGO-(0.25CuO-0.75ZnO) composites are 9.32, 58.53, 54.14, 25.21, and 69.27 F/g, respectively. The formation ofa double metal-oxide structure as well as their insertion into the rGO sheet can significantly improve the electrochemical properties of the supercapacitor.
... GCD analysis was further employed to compute the specific capacitance (C s ) with Eq. 4 [37,38]. 1870.06 ...
... The mechanisms are such that as direct current is passed and electrolytes interact at the anode and cathode, the added organic chemicals produce unsolicited degradation by-products in the plating liquids which must thereafter be removed by the use of AC. The extreme formation of these unwanted byproducts can harmfully influence the features and quality of the finished metals if not removed by the use of activated carbon (Faraji and Ani, 2015;Maher et al., 2021). ...
Groundwater contamination with elevated levels of fluoride has been an age-long environmental problem in many countries including Nigeria. Adsorption is an effective defluoridation technique; however, most of the effective adsorbents are not readily available. It is therefore necessary to explore the adsorptive potentials of local materials such as Raffia Palm Shells (RPS) for fluoride containment in groundwater. This study was designed to produce and characterise activated carbon from RPS for groundwater defluoridation.
Fluoride contents of groundwater in Makurdi, Nigeria, were determined using 63 samples collected from boreholes in 21 locations following standard procedures. The USEPA Hazard Quotient (HQ) was used to evaluate the human health risk potentials in relation to fluoride contamination for infants, children, teenagers and adults. The RPS were sourced from Ugbema market in Benue state and processed into activated carbon using phosphoric acid as activating agent. Response Surface Methodology (RSM) was used to optimise the quality (Specific Surface Area (SSA) and Carbon Yield (CY)) of Raffia Palm Shell Activated Carbon (RPSAC). The surface of RPSAC was coated with aluminium hydroxide to produce Aluminium-oxide-Coated-RPSAC (ACRPSAC) using functionalization principle. Physical characteristics (Brunauer-Emmett-Teller Surface Area (BETSA), Bulk Density (BD), Moisture Content (MC), Total Pore Volume (TPV), Average Pore Diameter (APD) and pHpzc) of the adsorbents were determined using standard methods. Adsorbents’ surface compositions were determined by SEM/EDX, FTIR and XRD analyses. Groundwater defluoridation potentials of the adsorbents were evaluated using batch adsorption method in comparison with a Commercial Activated Carbon (CAC). Linear regression and ANOVA at α0.05 were used to analyse the data sets.
The fluoride contents in the water exceeded the WHO limit of 1.5 mg/L in 33.3 % of the samples and ranged from 0.32 – 2.06 mg/L (mean=1.26±0.41). The HQ exceeded the threshold value of 1 in 66.7, 71.4, 52.4 and 9.5 % of the water samples for infants, children, teenagers and adults, respectively. Optimum conditions for the synthesis of RPSAC were 524 oC, 77.0 %, 4.00 g/mL and 104 minutes for temperature, concentration, impregnation ratio and time, respectively. The optimized values of SSA and CY were 1762.93 m2/g and 78.0 %, respectively. The physical characteristics of RPSAC and ACRPSAC were 456.1 and 715.8 m2/g, 0.45 and 0.37 g/cm3, 18.5 and 4.2 %, 0.25 and 0.47 cm3/g, 2.13 and 1.85 nm, 2.10 and 4.05 for BETSA, BD, MC, TPV, APD and pHpzc respectively. The SEM/EDX showed that the adsorbents had both micro and meso-porosities. The abundance of hydroxyl functional groups on the adsorbents’ surface was evident. The RPSAC was found to be amorphous, while the ACRPSAC was microcrystalline due to the formation of graphite-like structures. Batch fluoride adsorption performances of the adsorbents were in the order of ACRPSAC > RPSAC > CAC (removal efficiency= 80.0–99.0%) and were significantly different. Fluoride removal obeyed the Langmuir (R2=0.8802–0.9751) and Pseudo second order (R2=0.9974–0.9999) models which signified that its adsorption by the adsorbents was chemisorption-controlled.
Aluminium-oxide-coated raffia palm shell activated carbon is a suitable adsorbent for groundwater defluoridation in batch systems.
... Recently, porous carbon electrodes have become promising in supercapacitors or electrical-double-layer capacitors (EDLCs), which can store electrical energy at the electrode/electrolyte interface. Various carbon forms can be used as electrode materials such as graphene [3], carbon nanotube (CNT) [4], activated carbon (AC) [5], and carbon fiber (CF) [6]. ...
Novel carbon fiber (CF) mats were fabricated from tobacco leaf-based carbon dots (TL-CDs) filled rubber wood chip-extracted lignin (RWC-L)/polyacrylonitrile (PAN) composite fibers with a hybrid doping method. The ex-situ doping was applied during fiber formation via electrospinning by adding functionalized TL-CDs in the spinning solution. The in-situ doping was carried out in carbonization process for nitrogen (N) and oxygen (O) atom generation by utilizing RWC-L and PAN as a mixed precursor. The CF properties and electrochemical performances were evidently influenced by TL-CD content and carbonization temperature. The CF fabric containing 0.4 % w/v of TL-CDs and carbonized at 1200°C provided optimal specific capacitance (Cs ≅ 225 F g⁻¹), energy density (ED ≅ 53 W h kg⁻¹), and power density (PD ≅ 130 W kg⁻¹) at a current density of 0.2 A g⁻¹ in 6 M KOH electrolyte. It also had excellent cycling stability of ≅ 90% after 12000 cycles at a current density of 5 A g⁻¹. This could be combined effects of a small fiber diameter (≅ 0.65 μm), a high heteroatom content (≅ 21 wt% of N and O atoms), a large surface area (≅ 1063 m² g⁻¹), a high micropore volume (≅ 2.41 cm³ g⁻¹), high graphitic carbon (ID/IG ratio ≅ 0.97), and high electrical conductivity (≅ 62 S cm⁻¹). Moreover, the electrochemical properties of the TL-CD added CF sheet were superior to those of the bare CF mat. Therefore, this work introduces a sustainable and efficient approach to develop lignin-based CF fabrics as self-standing electrodes for advanced energy-storage devices.
... The specific capacitance (C sp in Fg -1 ) was calculated following a reported (Maher et al. 2021;Sivachidambaram et al. 2017) equation (1) using the data obtained for AC-MWCNTs electrode from GCD and CV measurements. ...
An Electrical double-layer capacitor (EDLC) has been fabricated with activated carbon (AC) and multi-walled carbon nanotubes (MWCNTs), which in turn were synthesized from Pongamia pinnata fruit shell and its seed oil, respectively. The activated carbon was produced by the chemical activation process at varying carbonization temperatures from 600-900 °C for 5 hours in N2 atmosphere. The obtained activated carbon had a high surface area of 1170 m2 g-1 and a total pore volume of 0.5907 cm3 g-1. The surface area of MWCNTs was 216.1 2 m2 g-1 and the total pore volume was 1.5067 cm3 g-1. The as-prepared AC and MWCNTs were characterized by surface area analysis using Brunner-Emmett-Teller method (BET), X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopic analysis, Field emission scanning electron microscopy (FESEM), High-resolution transmission electron microscopy (HR-TEM), Energy-dispersive X-ray spectroscopy (EDAX) and DFT (Density functional theory). The electrochemical performance of AC-MWCNTs (25:75) Stainless steel (SS) electrode and Graphite sheet electrode (GE) were studied by cyclic voltammetry, Galvanostatic charge-discharge and electrochemical impedance spectroscopy using 0.5 M Na2SO4 aqueous electrolyte. It has shown a specific capacitance of 174 Fg-1 and 95.26 Fg-1 respectively, using the three-electrode system at a current density of 1 mA g-1. The AC-MWCNT (25:75) SS electrode has exhibited excellent specific capacitance (CSP) and its Specific energy density and Power density were greater than AC-MWCNT (25:75) GE. The electrochemical performance of AC-MWCNT (25:75) SS electrode was identified as a suitable, low-cost and promising energy storage device for future generations. The present investigation attempts to promote the supercapacitor device in the context of available and future technologies for alternative energy systems with outstanding performance.
... Therefore, these properties, i.e., energy and power, are crucial from a practical point of view. The so-called Ragone plot (Figure 1) is the best way to compare various systems' performance [4]. ...
... The anionic redox-active electrolytes contain halides (iodide [14, [42][43][44], bromide [4,45], pseudohalides (thiocyanate [41], selenocyanate [46]), organometallic complexes (ferricyanide and, ferrocyanide [21,[47][48][49][50][51][52][53]) and organic anion-like indigo carmine [54]. ...
Electrochemistry is strongly related to redox reactions. Charge transfer processes are used for the current generation in all electrochemical cells. Nowadays, redox reactions are still of evitable importance for energy storage/conversion technology. For instance, the charge and discharge of batteries exploit redox reactions. Moreover, these processes can also be used to improve the operating parameters of other energy storage devices like electrochemical capacitors. Although, in principle, the energy in electrochemical capacitors is stored in an electrostatic manner (by electrical double-layer formation), the redox reactions introduce an additional charge and improve the energy of these systems. This chapter presents the principles of electrochemical capacitors’ operation and provides comprehensive insights into this technology with special attention focused on hybrid systems, exploiting the redox activity of the electrolytic solution.
