Symmetric Supercapacitor Cell Research Articles

Unveiling the Supercapacitive Performance of B, P Dual‐Doped Graphene in Triple Redox Additives

AbstractDual heteroatom doping of graphene is currently presumed as more promising for energy storage applications. In addition, the development of energy density with multiple redox additives is paying special attention. Here, we report the fabrication of B, P dual‐doped graphene in three various weight combinations. The formation and the quantity of the prepared samples were investigated by XRD, FT‐IR, EDAX and XPS. The B, P dual‐doped graphene derived from the weight ratio of boron and phosphorus dopant in 1 : 3 has achieved an enriched gravimetric capacitance of 360 F g−1 at 1 A g−1 (1 M H2SO4) and greater than RGO (151 F g−1). The energy density of the fabricated symmetric supercapacitor cell is found to be 50 Wh kg−1 in triple redox additives in 1 M H2SO4 solution which is greater than KI (33 Wh Kg−1) and 1 M H2SO4 alone (5 Wh Kg−1) at 2 A g−1. Also, the same cell delivered an increased stability of 99.7 % of capacitance retained from its initial value after 7000 charge–discharge cycles at 5 A g−1.

Porous α-Fe2O3 Hollow Rods/Reduced Graphene Oxide Composites Templated by MoO3 Nanobelts for High-Performance Supercapacitor Applications.

Porous α-Fe2O3 hollow rods/reduced graphene oxide (α-Fe2O3 HR/RGO) composites with unique morphological characteristics and a high surface area are prepared through a template strategy, which was systematically studied and found to have outstanding supercapacitive properties. When served as active material in a three-electrode setup, the optimized α-Fe2O3 HR/RGO-30, comprised 76.5 wt% α-Fe2O3 and 23.2 wt% RGO, was able to offer the largest specific capacitance of 426.3 F g-1, an excellent rate capability as well as satisfactory cycle life with capacitance retention of 87.7% and Coulombic efficiency of 98.9% after continuously charging/discharging at 10 A g-1 for beyond 10,000 cycles. Such electrochemical behaviors of the α-Fe2O3 HR/RGO-30 electrode can rival or even surpass those of many Fe2O3-based electrodes documented in the previous literature. Later, a symmetric supercapacitor cell of α-Fe2O3 HR/RGO-30//α-Fe2O3 HR/RGO-30 was fabricated. The assembled device offers the maximum energy density of 18.7 Wh kg-1, and also exhibits commendable rate capability, and features stable cycling durability (with capacitance retention of 83.2% together with a Coulombic efficiency of 99.3% after 10,000-cycle charge/discharge at 5 A g-1). These notable electrochemical performances enable the α-Fe2O3 HR/RGO-30 composite to be a high-potential material for advanced energy storage systems.

Solid solution-typed defect concept in forming multivalent cations- and oxygen vacancy-filled MnCo2O4-z spinel bifunctional electrodes for innovative symmetrical supercapacitor

Oxygen vacancies-filled MnCo2O4-z (MCO) nanosheets prepared by a two-step process with varied NH4F content have been investigated. MCO prepared with NH4F at 10 mmol (MCO-10) shows excellent to be used not only for cathode and anode but also for a symmetric supercapacitor cell (SSC). This MCO-10 electrode as a cathode not only reaches a high specific capacitance (Cs) of 7249 F/g at 1 A/g but also performs a high value of 2515 F/g at 1 A/g as an anode. An enlarged SSC of 5 × 5 cm2 is developed. One and five light-emitter-diode (LED) bulbs and commercial 100 F supercapacitor devices are tested to authenticate our reported data. The outstanding performance of nonstoichiometric MCO spinel involving the OH− dipole interaction with oxygen vacancies, chemical redox reaction, multiple cationic valence states, and oxygen vacancies-filled defective structure are all connected with the solid solution-typed defect concept to form bifunctional spinel.

Incorporating Gadolinium Oxide (Gd2O3) as a Rare Earth Metal Oxide in Carbon Nanofiber Skeleton for Supercapacitor Application

AbstractIn this study, we synthesized gadolinium oxide nanoparticles (Gd2O3 NPs) incorporated heteroatom‐doped microporous carbon nanofibers (CNF) to serve as electrode materials for enhancing supercapacitive energy storage. Our primary focus is on elucidating the impact of these hybrid electrode materials on key supercapacitor performance properties such as specific capacitance, specific energy, and specific power. To comprehensively assess the structural and chemical attributes of Gd2O3 NPs‐incorporated heteroatom‐doped microporous CNFs (CNF/Gd2O3) we employed an array of advanced characterization techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy (RAMAN), X‐ray diffraction (XRD), and X‐ray photoelectron spectroscopy (XPS). Our research has yielded impressive results, demonstrating a significant increase in supercapacitive performance. Specifically, the CNF/Gd2O3‐1 symmetric supercapacitor cell (SSC) has demonstrated a good specific capacitance of 162.3 F/g and a high specific energy of 8.12 Wh/kg at a specific power of 300 W/kg. These findings could be a new pathway to prepare composite electrodes for use in energy storage applications and promote further development for other rare‐earth nanostructures.

An azo functionalized anthraquinone as organic electrode materials for efficient pseudocapacitors with excellent cycling stability

Organic electrode materials (OEM) are attractive candidates for fabrication of pseudocapacitors (PSCs) to resolve the current problems related to low energy density and lower cycling stability. These problems can be effectively addressed by designing OEM electrode materials for PSC applications. Herein, we report the synthesis of 2,6-bis((E)-(4-hydroxyphenyl)diazenyl)anthracene-9,10-dione (AZOAQ) and utilized for fabrication of AZOAQ/graphene foil (GF) electrode. The two-electrode symmetric supercapacitor (SSC) cell made of the AZOAQ/GF show remarkably higher specific capacitance (Csp), excellent energy and power densities compared to reported OEMs. The SSC device made from AZOAQ/GF achieves specific capacitance (Csp) of 159.12 F g−1 at 0.5 A g−1 current density, remarkable than reported for SCs based on OEMs. The higher conductivity exhibited high energy density of 28.64 Wh kg−1 at power density of 1080.02 W kg−1. The SSC cell also displayed outstanding cycling stability with capacitance retention of 93.22 % after 10,000 galvanostatic charging/discharging (GCD) cycles. Furthermore, considering the simple molecular design for OEM electrode material, the proposed AZOAQ molecule would be an attractive, cheaper molecule for large-scale synthesis and fabricating organic electrodes for different energy storage applications in the future.

Surfactants effect on the electrochemical properties of FeSe2 electrode for supercapacitor with first principles insights into quantum capacitance

Nanostructured material like FeSe2 has been synthesized through a simple and cost-effective hydrothermal method. The effect of cationic, non-ionic, and anionic surfactants has been studied on the structural, morphological, and electrochemical properties of FeSe2 electrode material. The FeSe2 electrode material prepared with the assistance of CTAB surfactant displayed a superior specific capacitance value of 401 F g −1 at a scan rate of 10 mV s −1 and 337 F g −1 at a current density of 3.3 A g −1, respectively. The maximum energy density of the symmetric supercapacitor cell fabricated with the same material is evaluated to be 47 Wh kg−1 at a power density of 1667 W kg−1. The addition of the surfactant cetyltrimethylammonium bromide (CTAB) during the synthesis process is found to have a significant impact on the charge storage capability of the material, which is attributed to an increase in active surface area, porosity, reduced crystallite size, and reduced bulk resistance, etc. The real-time use of CTAB-based FeSe2 symmetric cells has been verified via illuminating different voltage light-emitting diodes. Further, the electronic properties and the quantum capacitance of FeSe2 material synthesized without the assistance of any surfactant have been analyzed theoretically using first-principles density functional theory calculations. Acquired results unveil the potential growth of FeSe2 electrode material in energy storage applications.

In-situ synthesis of N, S co-doped electrode material by an environmentally benign method towards designing of high voltage (3.0 V) binder-free sustainable aqueous symmetric supercapacitor

In aqueous electrolyte based symmetric supercapacitor, the decomposition of water to evolve hydrogen and oxygen occurs in relatively lower potential window, thereby, limits its cell voltage and needs to be modified so as to achieve high energy density. This manuscript reports a novel greener approach for an in-situ synthesis of N, S co-doped reduced graphene oxide (N, S co-doped rGO-10/20) nanohybrids as porous electrode material for designing a binder-free and up-scaled mass-loaded (5.0 mg cm−2) high voltage (3.0 V) aqueous symmetric supercapacitor in water-in-salt (WIS), 17 m NaClO4 electrolyte. A fairly rich co-doping/integration of heteroatoms (N (7.2 %) and S (1.5 %)) into the rGO matrix takes place through the formation of C-N, C-S and C-SOx-C bonds. The N, S co-doped rGO-20 nanohybrids in three-electrode system shows the pseudocapacitive behavior with the electrochemical stability of potential window (ESPW) of 3.0 V. In two electrodes set-up, the optimized aqueous symmetric supercapacitor cell (SSC) in WIS shows the superb cell voltage at 3.0 V (highest reported to-date), a fairly high areal energy density@areal power density (0.256 (mWh cm−2)@5.239 (mW cm−2)) at 0.7 A/g with excellent capacitance retention (93.7 %) and Coulombic efficiency (99.3 %) after 20 k cycles. Its energy storage capability is further validated by illumination of 125 white LEDs and 91 green LEDs upon lighting a single SSC for 50 s each and forming the tandem device with high cyclic stability (102 %). Under open circuit, SSC exhibits self-discharge to 2.4 V without any further appreciable discharge till 24 h.

Enhanced energy density of quasi‐solid‐state supercapacitor based on activated carbon electrode derived from honeycomb and gel polymer electrolyte with redox‐additive methylene blue

AbstractIncorporation of redox nature at the electrode‐electrolyte interface is of the current research approach for enhancing the specific capacity as well the energy density of the carbon supercapacitor. In the present studies, symmetric carbon supercapacitor cells are fabricated by using gel polymer electrolytes (GPEs) with and without addition of redox‐additive (MB) and activated carbon (AC) extracted from natural bio‐waste honeycomb (HCAC). The redox‐additive polymeric electrolyte offers high room temperature ionic conductivity (σRT ~ 2.3 × 10−3 S cm−1) and electrochemical stability window of ~1.4 V on the addition of 0.1 g of MB. The HC‐based activated carbon (HCAC) offers high surface area ~ 586 m2 g−1 and dominant meso‐porosity. The performance optimization of the supercapacitor cells are examined by using cyclic voltammetry, charge‐discharge (CD) and electrochemical impedance spectroscopy (EIS) techniques. The supercapacitor with redox‐additive GPE shows the electric double layer features along with faradaic reaction at the electrode‐electrolyte interface, which offers high capacitance ~114 F g−1 and specific energy ~7.76 Wh kg−1 at a power density 0.49 kW kg−1, which is almost ~2.5 times higher than the supercapacitor cell without redox‐additive GPE. Furthermore, the supercapacitor cell with 0.1 g MB redox‐additive based electrolyte shows almost stable capacitance up to 10 000 CD cycles with ~36% initial fading.

Development of Modified Mesoporous Carbon from Palm oil Biomass for Energy Storage Supercapacitor Application

Energy storage system research including battery and supercapacitor devices has been studied to increase efficiency, lower their cost and improve environmental friendliness. Supercapacitor (SC) device offers high transient response and power density which suitable for many applications. The electrodes in supercapacitor device usually produced from highly porous carbon materials. In this study, the modified mesoporous carbon was produced from Palm empty fruit bunch (EFB) biomass. The production of mesoporous carbon was done using a low-temperature hydrothermal carbonization process. The mesoporous carbon from EFB biomass has shown good properties in terms of high surface area and porosity. To improve the electrical conductivity of the carbon the modification by nitrogen doping with ammonium chloride and urea was studied. The effect of different nitrogen sources on surface area and pore properties were reported. The modified mesopore carbon was tested in a symmetrical swagelok supercapacitor cell to evaluate the specific capacitance and efficiency using galvanostatic charge-discharge method. The modified mesoporous carbon with urea doped exhibits the highest specific capacitance of 121 F g-1 at current loading of 0.1 A g-1 in an aqueous 1M H2SO4 electrolyte. The modified mesoporous carbon with urea doped has lower internal resistance due to nitrogen from urea enhance the electronic conductivity of the electrodes and thus increase the supercapacitor performance.

Tailoring potential window of aqueous electrolyte via steric molecular engineering for high voltage supercapacitors

Manufacturing economical and environmentally friendly aqueous electrolytes having a large operating potential is crucial to accomplish safe, high-energy and long-life supercapacitors. An emerging approach of superconcentrated Water-in-Salt (WIS) electrolyte significantly improves the performance through a stable, improved thermodynamic potential of water by reducing the free water molecules in the electrolyte. However, this approach raises concern about the cost and toxicity. By the way, we have achieved a similar performance by creating a hydrogen bonding network through the incorporation of additive with electrolyte, which suppresses the water electrolysis even at low salt concentration. This work demonstrates a hydrogen bond constructed electrolyte (Steric effect) using the additive to reduce water activity. In that way, it delivered an extensive operational voltage (>2.3 V) to the electrolyte at a low salt concentration (5M NaClO4). Further, the carbon-based symmetric supercapacitor cell with this electrolyte delivered a capacitance of 112 mF with good capacitance retention (71.4%) after 50,000 cycles. Further, the cell showed its excellency via a low self-discharge rate and leakage current. The performance of the coin cell-type supercapacitor is evaluated as per IEC standards and as well as the traditional method and compared with superconcentrated Water-in-Salt NaClO4. This work opens up new direction for designing high-voltage water-based electrolyte for inexpensive and very stable energy storage devices.

Flexible Polymer-Ionic Liquid Films for Supercapacitor Applications

Mechanically and thermally stable novel gel polymer electrolytes (GPEs) have been prepared and applied in supercapacitor cells. Quasi-solid and flexible films were prepared by solution casting technique and formulated by immobilization of ionic liquids (ILs) differing in their aggregate state. A crosslinking agent and a radical initiator were added to further stabilize them. The physicochemical characteristics of the obtained crosslinked films show that the realized cross-linked structure contributes to their improved mechanical and thermal stability, as well as an order of magnitude higher conductivity than that of the non-crosslinked ones. The obtained GPEs were electrochemically tested as separator in symmetric and hybrid supercapacitor cells and showed good and stable performance in the investigated systems. The crosslinked film is suitable for use as both separator and electrolyte and is promising for the development of high-temperature solid-state supercapacitors with improved capacitance characteristics.

Electrochemical performance of supercapacitor electrodes based on carbon aerogel-reinforced spread tow carbon fiber fabrics

Fabric-based supercapacitor electrodes were fabricated by embedding spread tow carbon fiber fabrics, in monolithic, bicontinuous carbon aerogels (CAG). The incorporation of CAG, at less than 30 wt%, increased the specific surface area of the CAG-CF fabric to above 230 m2 g−1 and the pore volume to about 0.35 cm3 g−1, orders of magnitude higher than that for the as-received carbon fibres. The presence of the CAG not only improves the electrochemical performance of the composite electrodes but may enhance the mechanical response due to the high stiffness of the aerogel structure. Cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance measurements were performed on symmetric supercapacitor cells consisting of two CAG-reinforced fabrics in an ionic liquid electrolyte. The specific capacitance of the symmetric supercapacitor was determined to be in the range 3–5 F g−1, considerably higher than that for the plain carbon fibers. Since optimum structural electrolytes are not yet available, this value was normalized to the total mass of both electrodes to place an upper bound on future structural supercapacitors using this spread tow CAG-CF system. The maximum specific energy and specific power, normalized to the total mass of the electrodes, were around 2.64 W h kg−1 and 0.44 kW kg−1, respectively. These performance metrics demonstrate that the thin CAG-modified spread tow fabrics are promising electrodes for future use in structural supercapacitors. In principle, in future devices, the reduced ply thickness offers both improved mechanical properties and shorter ion diffusion distance, as well as opportunities to fabricate higher voltage multicell assemblies within a given component geometry.

One-step strategy of 3D hierarchical porous carbon with self-heteroatom-doped derived bread waste for high-performance supercapacitor

Bio-waste is a promising carbon source that can be used as a basic component in renewable supercapacitors due to its abundant hierarchical pore structure potential, heteroatom self-doping capability, high surface area, as well as well-defined chemical and mechanical stability. This study converted bread bio-waste into rich 3D hierarchical porous carbon through a one-step facile strategy to be used as the main component of a supercapacitor. The porous carbon was obtained through physical activation approach at different temperatures of 750, 800, 850, and 900 °C without being combined with chemical activation. The optimized activated carbon illustrated high porosity behavior with an abundant 3D hierarchical pore structure consisting of 76.98% micropores and 23.02% mesopores and also produced a well-defined wettability of self-doping heteroatoms. Moreover, the electrochemical behavior in a symmetric supercapacitor cell showed a high specific capacitance of 202 F g−1 at 1 A g−1 with a rate capability of 73% at 10 mV s−1 in a 1 M H2SO4 electrolyte. It was also discovered that the activation temperature of 850 produced the highest energy density of 11.61 Wh kg−1 at a power density of 156.71 W kg−1 with a low equivalent series resistance of 0.11 Ω. Finally, the proof-of-concept showed that bread waste has immense potential as a 3D hierarchical porous carbon source after the synthesis through a single-stage facile approach and can be used as a major renewable electrode component for sustainable supercapacitors.

Nanoporous Hollow Carbon Spheres Derived from Fullerene Assembly as Electrode Materials for High-Performance Supercapacitors

The energy storage performances of supercapacitors are expected to be enhanced by the use of nanostructured hierarchically micro/mesoporous hollow carbon materials based on their ultra-high specific surface areas and rapid diffusion of electrolyte ions through the interconnected channels of their mesoporous structures. In this work, we report the electrochemical supercapacitance properties of hollow carbon spheres prepared by high-temperature carbonization of self-assembled fullerene-ethylenediamine hollow spheres (FE-HS). FE-HS, having an average external diameter of 290 nm, an internal diameter of 65 nm, and a wall thickness of 225 nm, were prepared by using the dynamic liquid-liquid interfacial precipitation (DLLIP) method at ambient conditions of temperature and pressure. High temperature carbonization (at 700, 900, and 1100 °C) of the FE-HS yielded nanoporous (micro/mesoporous) hollow carbon spheres with large surface areas (612 to 1616 m2 g-1) and large pore volumes (0.925 to 1.346 cm3 g-1) dependent on the temperature applied. The sample obtained by carbonization of FE-HS at 900 °C (FE-HS_900) displayed optimum surface area and exhibited remarkable electrochemical electrical double-layer capacitance properties in aq. 1 M sulfuric acid due to its well-developed porosity, interconnected pore structure, and large surface area. For a three-electrode cell setup, a specific capacitance of 293 F g-1 at a 1 A g-1 current density, which is approximately 4 times greater than the specific capacitance of the starting material, FE-HS. The symmetric supercapacitor cell was assembled using FE-HS_900 and attained 164 F g-1 at 1 A g-1 with sustained 50% capacitance at 10 A g-1 accompanied by 96% cycle life and 98% coulombic efficiency after 10,000 consecutive charge/discharge cycles. The results demonstrate the excellent potential of these fullerene assemblies in the fabrication of nanoporous carbon materials with the extensive surface areas required for high-performance energy storage supercapacitor applications.

Novel macaroni‐sponge‐like pore structure biomass (Zingiber officinale Rosc. leaves)‐based electrode material for excellent energy gravimetric supercapacitor

AbstractBACKGROUNDBiomass‐based porous carbon as the basic component of electrodes has received wide interest as a renewable energy storage device with high chemical–physical stability and environmental friendliness. Therefore, novel biomass waste based on Zingiber officinale Rosc./red ginger leaves was synthesized as an electrode‐based carbon material with an abundance of unique macaroni‐sponge‐like hierarchical pore structure, as well as good chemical, physical and economic performance. Template/metal–organic framework‐free red ginger leaf‐based hierarchical porous carbon (RGPC) was prepared using a facile and zero‐residue technique as electrode material for supercapacitor application.RESULTSAdditionally, ZnCl2 impregnation with concentrations of 0.1, 0.3 and 0.5 mol L−1 was utilized for increasing the active sites between electrode and electrolyte ions through interconnecting microchannels. The combination of macaroni‐sponge‐like structure, amorphous nature, optimum specific surface area and availability of oxygen functional groups as a self‐doping heteroatom of RGPC‐0.3 greatly optimized the electrochemical performance of symmetric supercapacitor cells. The RGPC‐0.3 electrode had an ideal specific capacitance of 215.76 F g−1 with a specific energy of 29.966 Wh kg−1 and maximum specific power of 108 W kg−1 at 1 mV s−1 in a symmetric supercapacitor system. Furthermore, a relatively good coulombic efficiency of 71.01% was obtained with a low equivalent series resistance of 0.098 Ω.CONCLUSIONSThis study provides insight into the generation of unique hierarchical porous carbon as a basic component of electrodes for energy storage applications with high electrochemical performance through the utilization of waste red ginger biomass with a simple, facile and cost‐effective strategy. © 2022 Society of Chemical Industry (SCI).

Oriented attachment of carbon/cobalt-cobalt oxide nanotubes on manganese-doped carbon nanofibers for flexible symmetric supercapacitors

Electrodes for flexible supercapacitors were fabricated from manganese-doped carbon nanofibers (Mn-CNF) decorated with carbon-coated Co-CoOx (C/Co-CoOx) nanotubes. The Mn-doped polyacrylonitrile (PAN)–2-methylimidazole (2MI) solution was electrospun using optimized Mn concentrations and ZIF-67 was then surface loaded by wet impregnation with added polyvinylpyrrolidone (PVP). These ZIF-67 loaded Mn-fibers, when annealed, resulted in carbon-coated C/Co-CoOx nanotubes on the Mn-CNF surface. In the presence of PVP, ZIF-67 oriented attachment occurs, forming evenly dispersed CoOx particles even after high temperature annealing. XRD spectra exhibit the formation of metallic Co nanoparticles (NPs), whereas Raman spectra and XPS indicate Co particle oxidation. A carbon coating limits the oxidation of Co; thus, the particles are called C/Co-CoOx. A symmetric supercapacitor cell prepared using the CNFs decorated with C/Co-CoOx using an aqueous electrolyte has a capacitance of 1263 mF⋅cm−2 at a current density of 0.25 mA⋅cm−2 and a wide potential window of 1.4 V for the optimal case. Long-term cycling showed 110 % capacitance retention after 10,000 cycles. Moreover, bending tests and powering LEDs demonstrated the flexibility and improved charge storage of the prepared nanofiber electrodes.

High-performance hybrid supercapacitor-immobilized Wells-Dawson polyoxometalates on activated carbon electrodes.

The nanofabrication of electroactive hybrid materials for next-generation energy storage devices is becoming increasingly significant as supercapacitor (SC) technology develops rapidly. The present study utilizes activated carbon (AC) templates reinforced with Wells-Dawson polyoxotungstates (POMs) to produce nanohybrid electrodes for high-performance supercapacitors. This study analyzes Wells-Dawson polyoxotungstates (P2W18) for the first time integrated with AC, and its structural and electrochemical performances are discussed. First, the electrochemical performances of symmetric supercapacitors were characterized in an acidic aqueous electrolyte (0.5 M H2SO4). It was observed that a supercapacitor cell containing the 5 wt% AC-P2W18 hybrid symmetric displayed a noteworthy specific capacitance of 289 F g-1 and a remarkable energy density of 40 W h kg-1. Moreover, 5% AC-P2W18 symmetric supercapacitor cells showed 89% cyclic stability over 4000 cycles. Three LED lights were charged onto the electrode. The LEDs continued to illuminate continuously for red until 160 seconds, yellow until 20 seconds, and blue until 10 seconds after removing the electrode from the electrochemical workstation, demonstrating the device's power and energy density.

The use of some sulfonic acids for improving aluminum current collector resistance

The corrosion behavior of aluminum current collectors in the standby and high-load modes was investigated by simulating via immersion and anodization experiments in electrolyte environments. The immersion experiments were carried out using aluminum alloy (AA5754) in camphorsulfonic (CSA), p-toluenesulfonic (PTSA), trifluoromethanesulfonic (TFMSA), and fluorosulfonic (FSA) acid solutions, and the results were compared with those of H 2 SO 4 and methanesulfonic acid (MSA). Corrosion resistance increased in the order of FSA, MSA, TFMSA, PTSA, H 2 SO 4 , and CSA. Thin-film XRD and XPS results revealed sulfonic acid adsorption to Al 2 O 3 . From AFM, the least rough and highest crystalline oxide layer was obtained with CSA, while FSA yielded the opposite. In addition, AA5754 was anodized in 0.1 M CSA, PTSA, and H 2 SO 4 solutions, and its corrosion behavior was examined. R ct values were about one hundred times higher than in the immersion experiments; besides, less rough and thicker layers were obtained on the surface owing to the controlled dissolution. The mixture of CSA:H 2 SO 4 (1:1) was used as an anodization solution, and the maximum resistance (5652 Ω.cm 2 ) was obtained at 20 V, which was a better corrosion behavior according to individual electrolytes. This could be due to the optimum combination of the high acidity of H 2 SO 4 and the ability of CSA to block the surface sites thanks to its larger cyclic structure. Finally, a symmetric supercapacitor cell prepared using a carbon-coated Al current collector in PVA/H 2 SO 4 :CSA gel electrolyte was tested by cyclic voltammetry and GCD. The cell provided 26 Wh.kg -1 and 10.2 kW.kg -1 with 89% efficiency and 64% retention after 5000 cycles over a wide potential range of 1.6 V, exhibiting better capacitive performance than the gel electrolyte without CSA. This increase could be because CSA contributes to the growth of the protective aluminum oxide layer as an anionic surfactant. • Sulfonic acids are adsorbed on aliminum alloy surface during immersion and anodization • Al 2 O 3 has the least rough and highest crystalline in the presence of camphorsulfonic and p-toluenesulfonic acids • The corrosion resistance of AA5754 significantly improves by anodization in the mixtures of sulfonic acids with H 2 SO 4 • Supercapacitor with Al current collector operates in a wide potential range of 1.6 V in PVA/H 2 SO 4 :CSA • The cell provides 26 Wh.kg -1 and 10.2 kW.kg -1 with 89% efficiency

Irradiated rGO electrode-based high-performance supercapacitors: Boosting effect of GO/rGO mixed nanosheets on electrochemical performance

Supercapacitors are seemed to be one of the most promising choices as an energy storage system. However, there is still a gap in enhancing its energy density values and cyclic stabilities throughout a facile approach. Herein, it was aimed to propose a facile and effective way to fabricate high-energy supercapacitor electrode material based on reduced graphene oxide (rGO) nanostructure. Bearing this in mind, the bulk rGO powder was irradiated by various beam sources including Co-60, Am-241, Na-22, and Sr-90, and the resultant irradiated rGO samples were utilized as the electrode active material to fabricate symmetrical supercapacitor cells. The irradiated rGO samples were characterized both physicochemically and electrochemically. The physicochemical characterizations revealed that as a consequence of the irradiation, both GO and rGO nanosheets were formed in the resultant powder and the d-spacing of the graphene nanosheets were expanded. The highest electrochemical performance metrics were acquired for Sr-90 irradiated rGO electrode-based supercapacitor cell with the specific capacitance value of 585.44F.g−1 at 0.2 A.g−1, and outstanding capacitance retention performance of 97.14% for the 5000th CV cycles at 200 mV.s−1. Moreover, the energy density and power density values were comparable to other commercial energy storage systems such as lead-acid and nickel-metal hybrid batteries. Hence, it can be speculated that these pioneering breakthroughs could pave the way for cutting-edge high-energy supercapacitors based on rGO-derivatives with superior electrochemical performance metrics, as well as engineering of high-performance rGO-based materials to be employed in various energy applications.

Unveiling the surface dominated capacitive properties in flexible ternary polyaniline/NiFe2O4/reduced graphene oxide nanocomposites hydrogel electrode for supercapacitor applications

The 3D ternary nanocomposites hydrogel have been effectively fabricated on carbon cloth using a two-step synthesis approach. Nickel ferrite nanoparticles (NiFe2O4) prepared by template method have been dispersed onto/within rGO nanosheets leading to the formation of NiFe2O4/rGO (NFG) nanocomposites. Afterward, polyaniline hydrogel has been polymerized on NFG nanosheets to prepare ternary polyaniline/NiFe2O4/rGO hydrogel (PNFG) nanocomposites on carbon cloth that can be further utilized as a binder-free supercapacitor electrode. The resulting 3D ternary nanocomposites hydrogel achieved maximum specific capacitance of 1134.28 F/g at a current density of 1 A/g and 76.46 % of capacitive retention at 10 A/g. The supercapacitor electrode exhibited outstanding rate capability and superior cyclic stability up to 5000 successive cycles. In addition, the symmetric supercapacitor cell delivered 0.61 kW/kg of specific power and 19.29 Wh/kg of specific energy. The excellent electrochemical characteristics of PNFG is ascribed to its well-designed 3D microstructure and the synergistic effect created by the capacitive mechanism due to electric double layer capacitance (EDLC) and pseudocapacitance (surface redox reactions) as well as diffusion-controlled mechanism (faradaic redox reactions). It has been revealed that the overall electrode reaction is dominated by surface-controlled processes, with a small contribution from diffusion-controlled faradaic processes.