High Specific Capacitance Value Research Articles

Uranium-based electrode material for the high-performance supercapacitors

In recent decades, significant progress has been made in the engineering of electrode materials for supercapacitors. In this regard, the primary emphasis has been on investigating carbonaceous based materials. However, this focus has restricted the overall capacitance of supercapacitor devices, thus hindering their broader application possibilities. There is still a gap in the literature on high-performance radioactive element-based electrode materials. Bearing this, in this work, a simple approach was suggested for the implementation of uranium, as a radioactive element, decorating onto carbon architecture, as electrode material in high-energy supercapacitor cells. Herein, a facile pathway for tailoring a uranium-decorated graphene oxide nanostructure (U-GOx; where x stands for the GO:U ratio by weight) was proposed and the potential applications of the synthesized nanoarchitectures as an electrode material of supercapacitor cell were investigated. As per the author's knowledge, for the first time in the ever-burgeoning field of energy storage systems, a radioactive compound-based supercapacitor cell was fabricated. The physicochemical characterizations confirmed the successful anchoring of uranium atoms onto the graphene oxide skeleton. The U-GO5 electrode-based-supercapacitor cell offered the highest performance metrics with a 95.92 % capacitance retention value at the end of the 15,000 consecutive galvanostatic charge-discharge cycles, besides the high specific capacitance value of 258.6 F⸱g−1 at a high current density value of 10.0 A⸱g−1. Moreover, the radioactivity measurements were conducted to investigate whether the fabricated supercapacitors were radioactive or not. The results revealed that the measured radiation dose of the U-GO5-based supercapacitor cell before the GCD cycles, which was of the highest uranium content, was ca.0.06 μSv (the background measurement was excluded). This finding indicated there would be no adverse effect on human health or the environment. It can be speculated that this work is a new era for engineering a high-performance supercapacitor based on organic electrodes decorated with a radioactive element.

Directed morphology engineering of 2D MoS2 nanosheets to 1D nanoscrolls with enhanced hydrogen evolution and specific capacitance

1D-molybdenum disulfide (MoS2) nanoscrolls displayed enhanced electrochemical properties compared to 2D-MoS2 nanosheet counterparts. Rolling of nanosheets is the main fabrication route to nanoscrolls. However, owing to the conflict between chemical stability and multiple bending, the morphology transition from nanosheets to nanoscrolls is quite challenging. Herein we describe a reversible morphology transition from nanosheets to nanoscrolls by utilizing non-covalent interactions between MoS2 nanosheets and phenothiazine based organic dye. Interestingly, nanoscrolls can easily be opened back into nanosheets by destroying the non-covalent interactions with organic solvents. The prepared nanoscrolls exhibited enhanced electrochemical properties than nanosheets. Compared to nanosheets, nanoscrolls exhibited comparatively lower overpotential with a Tafel slope of 141 mV dec-1 and high specific capacitance of 1868 F g−1. Hydrogen evolution by the Volmer-Heyrovsky mechanism being superior for the nanoscrolls is envisaged by the relatively increased availability of Hads sites at MoS2 edges induced by scrolling. Whereas the high specific capacitance value of nanoscrolls is ascribed to the enhanced electrical double-layer capacitance mediated charge storage, which arises due to the synergistic effect of both scrolled structure and the electron-rich phenothiazine-based dye.

A Hybrid Supercapacitor from Nickel Cobalt Sulfide and Activated Carbon for Energy Storage Application

Nickel–cobalt sulfide is a promising material for supercapacitor positive electrodes due to its high theoretical capacitance. Herein, the electrochemical properties of nickel–cobalt sulfide nanostructures synthesized via a two‐stage hydrothermal method are investigated and the synthesis conditions to achieve high mass loading while maintaining high specific capacitance are determined. The nanostructural morphology and effective mass loading of the electrodes (≈10 mg cm−2) enable the achievement of a high specific capacitance value of 8.1 F cm−2 at a current density of 5 mA cm−2. A hybrid capacitor is made using optimized nickel–cobalt sulfide electrodes as the positive electrode and activated carbon as the negative electrode. The device exhibits a maximum operation potential window of 1.75 V and an energy density of 51.2 Wh kg−1 at a power density of 262.5 W kg−1. Electrochemical measurements demonstrate that the device maintains a capacitance retention rate of 95% after 10 000 charge–discharge cycles within a working voltage of 1.8 V. High electrochemical performances compared with others devices‐based water electrolytes make it promising for the energy storage device.

Effect of Electrolyte Concentration on Characteristics of Activated Carbon of Cocoa Peel

Cocoa peel activated carbon has been successfully synthesized with 0.3 M KOH activator and NaCl electrolyte as the base material for supercapacitor electrodes. Variations in the concentration of NaCl electrolyte used were 1 M, 2 M, and 3 M to determine their effect on the capacitance, conductivity, and pore area values produced. The activated carbon produced was characterized by Scanning Electronic Microscope (SEM) to see surface morphology, X-Ray Diffraction (XRD) to determine carbon crystals, Cyclic Voltammetry (CV) and LCR-Meter to determine capacitance and conductivity values, and the Brunauer Emmett Teller method. (BET) to measure its surface area. The results of the Indonesian National Standard (SNI) test results obtained water content (8.6%), ash content (8.7%), volatile matter (26.2%), carbon content (65.1%), and iodine absorption (800 mg/g). The pore surface area can be increased by activation up to 24,742 m2/g. XRD analysis shows that the atomic structure is amorphous. Surface morphology proves that the increase in NaCl electrolyte concentration affects the pore structure. The higher the electrolyte concentration, the more even and finer the pore structure will be. The highest specific capacitance value was obtained at 3 M NaCl, which was 1.68375 F/g and the lowest was at 0.10771 F/g NaCl 1 M. The conductivity obtained is 1.83 S/m at 3 M NaCl at frequency of 1000 Hz and the lowest is 0.18 S/m at 1 M NaCl at 100 Hz. This proves that the electrolyte concentration can affect and increase the value of the capacitance and conductivity of the supercapacitor electrode.

CO2-Derived Nanocarbons with Controlled Morphology and High Specific Capacitance.

The conversion of CO2 to nanocarbons addresses a dual goal of harmful CO2 elimination from the atmosphere along with the production of valuable nanocarbon materials. In the present study, a simple one-step metallothermic CO2 reduction to nanocarbons was performed at 675 °C with the usage of a Mg reductant. The latter was employed alone and in its mixture with ferrocene, which was found to control the morphology of the produced nanocarbons. Scanning electron microscopy (SEM) analysis reveals a gradual increase in the amount of nanoparticles with different shapes and a decrease in tubular nanostructures with the increase of ferrocene content in the mixture. A possible mechanism for such morphological alterations is discussed. Transmission electron microscopy (TEM) analysis elucidates that the nanotubes and nanoparticles gain mainly amorphous structures, while sheet- and cloud-like morphologies also present in the materials possess significantly improved crystallinity. As a result, the overall crystallinity was preserved constant for all of the samples, which was confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. Finally, electrochemical tests demonstrated that the prepared nanocarbons retained high specific capacitance values in the range of 200-310 F/g (at 0.1 V/s), which can be explained by the measured high specific surface area (650-810 m2/g), total pore volume (1.20-1.55 cm3/g), and the degree of crystallinity. The obtained results demonstrate the suitability of ferrocene for managing the nanocarbons' morphology and open perspectives for the preparation of efficient "green" nanocarbon materials for energy storage applications and beyond.

Electrochemical performance of diazonium-generated carbon films for electrochemical double-layer capacitors (EDLCs)

Carbon-based electrode materials for energy storage systems have received considerable attention thanks to their excellent mechanical properties, large specific surface areas and moderate electrical conductivities. Here, diazonium-generated carbon films on the flexible carbon paper (CP) electrodes were prepared through electrochemical reduction of aryl diazonium salts bearing COOH, NO2, CH3 and H functional groups. The production of polymeric carbon films by diazonium modification method was preferred because it is a simple and effective process, and also the carbon-based films prepared by this method are covalently attached to the carbon electrode surfaces. The capacitive properties of the robust carbon films were assessed by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) in three-electrode and asymmetric device configurations. The results indicated that diazonium-generated carbon films on flexible substrates exhibited typical EDLC behavior with high specific capacitance values (237.6–446.9 F g−1 at 0.5 A g−1 current density), and also their capacitive performances were largely dependent upon the functional groups on the benzene ring. Overall, this work reveals that the diazonium modification method is a promising approach to create the carbon-based active electrode materials in advanced energy-storage systems.

Cheese-like hierarchical porous carbon material with large specific surface area derived from red dates for high performance supercapacitors

Red dates are rich in porous structure inside, and the carbonization process can easily inherit unique constructions, which is beneficial to the rapid transmission of ions. The specific surface area (SSA) and pore structure are the key factors that determine the energy storage performance of carbon material supercapacitors. In this paper, hierarchical porous carbon materials (RDKC-4-800) with cheese-like microstructure based on red dates were prepared by two steps of hydrothermal pre-carbonization and KOH carbonization activation. The obtained materials have a rich hierarchical pore structure and large SSA (1115.7 m2 g−1), which is conducive to ion and electron transport and contribute to excellent electrochemical properties. Electrochemical tests indicate a high specific capacitance value of 341.9 F g−1 for the material at a current density of 0.5 A g−1. The assembled supercapacitors exhibited an energy density of 10.9 W h kg−1 and a power density of 124.93 W kg−1, outperforming many biomass carbon supercapacitors studies under similar conditions reported in the literature. After 30,000 charge and discharge cycles at a current density of 5 A g−1, the capacitance retention rate is 81.29 % and the coulombic efficiency is 99.67 %. This study provides an efficient and concise method to prepare red dates porous carbon materials and demonstrates that red dates biomass can be effectively reused in the field of supercapacitors.

Fabrication of NiMn2O4 nanospheres and its hybrid with polyaniline for high energy and high power supercapacitor with long cycle stability

NiMn2O4 nanospheres have been prepared by a solution combustion method and hybridised with polyanilne by the dilute polymerization method. The metal oxide and its polymer hybrid forms were characterized by several physicochemical methods and microscopic techniques. The capacitive nature and cyclic stability were studied by cyclic voltammetry and galvanostatic charge–discharge measurements. The newly fabricated NiMn2O4 nanospheres and PANI-NiMn2O4 nanohybrid showed high specific capacitance values of 374 Fg−1 and 442 Fg−1 respectively, at the scan rate of 10 mVs−1. The NiMn2O4 nanospheres showed enhanced energy density (13.8 WhKg−1) compared to its hybrid form (2.82 WhKg−1). However, the power density of the PANI-NiMn2O4 nanohybrid (565.2 Wkg−1) was found to be higher than that of the pure NiMn2O4 nanospheres (447.18 WKg−1). In addition to that, both the electrode materials showed the same columbic efficiency (∼96 %) after 1000 consecutive cycles.

Enhanced magnetic, electrochemical and gas sensing properties of cobalt substituted nickel ferrite nanoparticles prepared by hydrothermal route

The cobalt doped nickel ferrite nanoparticles were successfully synthesized via hydrothermal method at low reaction temperature. X-ray diffraction analysis confirmed the cubic spinel structure with an average crystallite size of 41 nm for pure nickel ferrite (NF) and in the range (38–33) nm for substituted samples. High resolution transmission electron microscope observations revealed the cubic-like shaped nanosized particles. Ultraviolet diffuse reflectance spectroscopy indicated an increase in the energy bandgap with increasing Co content. X-ray photoelectron spectroscopy confirmed the oxidation states of constituents, +2 for Ni, +2 for Co, and +3 for Fe. The AC conductivity was enhanced with increasing frequency. The observed higher value of saturation magnetization and coercivity, manifests its suitability in high density recording media. Besides, the ratio of Hcr/Hc confirmed the pseudosingle domain nature of the synthesized nanoparticles. The valency and occupancy of the Fe ion in tetrahedral-A and octahedral-B sites within the spinel cubic structure were elucidated by Mossbauer spectroscopy analysis. The cyclic voltammetry (CV) studies revealed the pseudocapacitance behaviour with high specific capacitance value at low scan rates. The sensor activity towards liquified petroleum gas (LPG) at 100 ppm showed the response and recovery time as 52 and 13s respectively.

A two-pronged strategy to modulate the porosity of porous carbons for capacitors: The relative effects of the texture and fuel properties of carbonaceous matter

Based on the search for a novel method to modulate the texture properties of porous carbon, it is essential to demonstrate the relative influence of texture and fuel properties (i.e., the general term of volatile, fixed carbon, ash, elements, and calorific value) of carbonaceous matter. Herein, H3PO4 activation was applied to fabricate pine sawdust-derived porous carbons (PC-T; T can be 450, 500, 550, and 600) with various fuel and texture properties. Afterward, the pore architectures recorded for PC-T were adjusted using the CO2 activation procedure; that is, PC-T-derived porous carbons (PC-TC) were obtained. PC-TC showed a significant increase in texture properties (e.g., specific surface area and total pore volume) and specific capacitance compared to PC-T. In the three-electrode configuration, PC-550C achieved high specific capacitance values (e.g., 230.78 F/g at 0.5 A/g). The assembled PC-550C-based symmetrical supercapacitor achieved an impressive specific capacitance of 172.12 F/g upon 0.5 A/g. Interestingly, it equally delivered high energy density (23.91 Wh kg−1) and power density (47.30 kW kg−1), respectively. Further, the specific surface area of the PC-TC samples depends not only on the fuel properties of the PC-T samples but also on the texture properties of the PC-T samples. Superior fabricability and variable texture properties enable the two-pronged strategy (i.e., sequential H3PO4–CO2 activation) for producing bulk senior and multi-level porous carbons.

Special Section on 2D Materials for Electrochemical Energy Storage and Conversion

Electrochemical energy storage and conversion are currently one of the most critical challenges due to the increasing energy demand. Therefore, discovering novel materials to develop low-cost and more efficient energy storage technologies is urgently necessary. Among various novel materials, two-dimensional (2D) materials have attracted intensive research activities in multiple fields due to their fascinating physical and chemical properties. The 2D materials having a higher surface-to-volume ratio are beneficial to developing low-cost and large-scale energy storage systems for practical applications. There have been many promising concepts of 2D material-based real-life energy applications recently in batteries, supercapacitors, fuel cells, solar cells, thermoelectric, triboelectric generators, etc. Despite recent progress, significant efforts are still needed to investigate the fundamentals of 2D materials for electrochemical energy storage and conversion. Over the past few years, there has been substantial progress in modeling, theories, and experimental characterizations of 2D materials for energy storage and conversion. This timely Special Section issue addressed some recent advances in this critical area. We have selected eight papers covering a gamut of electrochemical-centric research in 2D materials for energy storage and conversion.In this issue, Qu et al. reported the electrochemical evaluation of helical carbon nanofibers (HCNFs) prepared by the ethanol flame method as anode materials of lithium-ion batteries. Their results show that HCNFs possess high reversible capacity, good rate performance, and excellent cycling stability. Farma et al. investigated a simple and cost-effective method to generate porous carbon activation from Palmae plant waste biomass, namely, areca leaf midrib (ALM). They showed that the electrochemical properties of activated carbon supercapacitor cells derived from ALM biomass have the highest specific capacitance value and scan rate in a two-electrode system. Arumugam et al. discussed a ternary composite made up of graphene oxide, polyaniline, and zinc oxide as an electrode material for supercapacitors with its structural and electrochemical properties. The ternary composite exhibited the highest specific capacitance. Metzger et al. focused on using graphene-coated proton exchange membrane (PEM) to reduce fuel crossover. They found that the adhesion of graphene on PEMs is insufficient for prolonging fuel cell operation, resulting in graphene delamination at high temperatures and higher fuel crossover values compared to lower temperature testing. Zaidi et al. reported the superior performance of graphene nanosheet (GNS) materials over Vulcan XC incorporated as a cathode catalyst in Li-O2 battery. The GNS catalysts demonstrated promising performance at higher current densities and with various organic electrolytes. Pandey et al. synthesized a mechanically stable, proton-conducting, and very cost-effective nanocomposite membrane using a simple and scalable phase-inversion approach. The synthesized proton-conducting nanocomposite membrane was demonstrated as a potential advanced functional solid electrolyte for possible application in proton exchange membrane fuel cells. Fauzi et al. reported the thermophysical properties of N,N-diethylethanolammonium chloride/ethylene glycol-DES (deep eutectic solvent) for the replacement of ionic liquid. They studied the physical properties of DES, which are thermal conductivity, viscosity, and surface tension. Finally, the review article by Zeng et al. provided an overview of the application of conductive diamond in electrocatalytic reduction and outlined the improvement of electrochemical properties by employing metal particles to modify the surface.We believe that this Special Section issue will be a valuable contribution to the energy storage and conversion literature and open new frontiers for researchers. The interdisciplinary field of 2D material-based energy storage is rapidly evolving. Our Special Section issue will motivate many researchers to implement novel techniques, such as artificial intelligence, digital twins, and automated advanced manufacturing, in this field and initiate new collaborations between experimentalists, theorists, and modelers. We would like to thank all contributors to this Special Section issue for submitting their latest high-impact work. Also, special thanks would go out to the invited reviewers for helping us further enhance the quality of the articles.

Synergistic redox activity of transition metal sulfide/polyaniline as electrode material for battery supercapacitor applications

The hybrid device, an eventual energy storage device, synchronizes the high-rate capability and power from supercapacitors and exceptional energy from batteries. Initially, we synthesized strontium sulfides, polyaniline, and strontium sulfide/PANI. These electrodes were functionalized initially in three electrode configuration employing 1 M KOH electrolytic medium. Among all the electrodes, the SrS/PANI has revealed astonishing results in comparison to its counterparts. To elaborate its practical applications, a hybrid device was fabricated manifesting high specific capacity values of 424.8 C/g (5 mV/s) and 252.56 C/g (0.7 A/g). Also, maximum energy of 59.6 Wh/kg was acquired by the device while having power of 595 W/kg. The assembled hybrid device was inspected to study its storage mechanism separately by using Dunn's model which validates theoretically the experimental outcomes. These results justify the exceptional performance of SrS/PANI composites, therefore can be recognized as novel promising contender for battery-supercapacitor applications.

Current collectors based on multiwalled carbon-nanotubes and few-layer graphene for enhancing the conversion process in scalable lithium-sulfur battery

We investigated herein the morphological, structural, and electrochemical features of electrodes using a sulfur (S)-super P carbon (SPC) composite (i.e., S@SPC-73), and including few-layer graphene (FLG), multiwalled carbon nanotubes (MWCNTs), or a mixture of them within the current collector design. Furthermore, we studied the effect of two different electron-conducting agents, that is, SPC and FLG, used in the slurry for the electrode preparation. The supports have high structural crystallinity, while their morphologies are dependent on the type of material used. Cyclic voltammetry (CV) shows a reversible and stable conversion reaction between Li and S with an activation process upon the first cycle leading to the decrease of cell polarization. This activation process is verified by electrochemical impedance spectroscopy (EIS) with a decrease of the resistance after the first CV scan. Furthermore, CV at increasing scan rates indicates a Li+ diffusion coefficient (D) ranging between 10−9 and 10−7 cm2·s−1 in the various states of charge of the cell, and the highest D value for the electrodes using FLG as electron-conducting agent. Galvanostatic tests performed at constant current of C/5 (1 C = 1675 mA·gS−1) show high initial specific capacity values, which decrease during the initial cycles due to a partial loss of the active material, and subsequently increase due to the activation process. All the electrodes show a Coulombic efficiency higher than 97% upon the initial cycles, and a retention strongly dependent on the electrode formulation. Therefore, this study suggests a careful control of the electrode in terms of current collector design and slurry composition to achieve good electrode morphology, mechanical stability, and promising electrochemical performance in practical Li-S cells.

Fabrication of dual functional 3D-CeVO4/MWNT hybrid nanocomposite as a high-performance electrode material for supercapacitor and L-Tryptophan detection

The development of a novel material with excellent properties for energy storage and sensors has been considered the best material to overcome the future energy demand and economic crisis. Herein, a three-dimensional (3D) hybrid nanocomposite (3D-CeVO4/MWNT HNC) was fabricated based on; i) synthesis of cerium vanadate nanoparticles (CeVO4 NPs) through simple precipitation, and ii) successful inclusion of CeVO4 NPs on multiwall carbon nanotube (MWNT) by using ultrasonication approach. To reveal the physicochemical parameters of 3D-CeVO4/MWNT HNC, X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR), powder X-ray diffraction (P-XRD), field emission-scanning electron microscopy (FE-SEM), transmission electron microscope (TEM), and electrochemical techniques are utilized. As synthesized 3D-HNC possessed the specific features of both CeVO4 NPs and MWNT exhibits high electrocatalytic behavior due to its high surface area and conductivity. It has been more attractive for the application of energy storage and as an electrochemical sensor. 3D-CeVO4/MWNT HNC reveals high specific capacity value of 378 C g−1 at 1 A g−1 with long cycle life with 90.8% retention. Also, the proposed sensor shows a low detection limit of 0.07 μM and sensitivity of 20.71 µA µM−1 cm−2 with a dynamic linear range of 2-322.5 μM. Then the resulting sensor was also applied to detect the L-Trp in the real-time sample. Hence 3D-CeVO4/MWNT HNC could be a promising material for both applications of the electrochemical sensor and supercapacitor.

Spray pyrolyzed hydrophilic nickel oxide electrodes with nano-granular morphology for a symmetric supercapacitor device

The symmetric supercapacitor device is efficiently invented using two identical sprayed nickel oxide thin film electrodes equipped via an aqueous path. Firstly, we did a comparative study of structural, morphological and electrochemical characterizations of nickel oxide electrodes which are prepared by varying concentrations of the precursors (0.2, 0.4, 0.6, 0.8 and 1.0 M and renamed according to their concentration as AC (Aqueous Concentration) AC-1, AC-2, AC-3, AC-4 and AC-5 respectively). XRD patterns of all electrodes confirm cubic crystal structure. The highest value of specific capacitance of NiO@AC-4 (0.8 M) electrode is 256.32 Fg−1 at 0.002 Vs−1 which is the maximum among all electrodes. The specific energy and specific power of the AC-4 electrode at 0.002 Acm−1 are 29.08 Whkg−1 and 3.06 kWkg−1 respectively. NiO@AC-4 electrode shows 69.42% retention in capacitance value after 5000 cyclic voltammetric cycles. The fabricated device parades specific capacitance (SC) 92.81 Fg−1 at 0.002 Vs−1. The wettability study depicts the hydrophilic nature of all electrodes (except the NiO@AC-1 electrode). As concentration increases morphology of the prepared electrodes changes from impenetrable to porous micro globules. SEAD pattern rings and XPS investigation are well matched with XRD analysis.

Synergistic effects of multifunctional nanostructured WO3-WS2 decorated on polypyrrole (WO3-WS2/PPy) for the removal of toxic heavy metals from wastewaters and high supercapacitor performance

Nowadays, developing a simple, economic, and scalable approach for environmental remediation and producing energy storage devices remains challenging. Herein, we report a novel WO3–WS2 decorated polypyrrole (WO3–WS2/PPy) nanocomposite for the removal of heavy metals, i.e., Cd(II) and Ni(II) and high-performance supercapacitor electrodes.The WO3–WS2/PPy showed significant improvement in the removal of Cd(II) (95.33%) and Ni(II) (89.95%), while WO3–WS2 and PPy revealed removal efficiency of 87.02 and 77.01% for Cd(II) and 82.97 and 74.66% for Ni(II), respectively. For the competitive adsorption experiment, Cu2+/Zn2+ causes a significant influence, while Na+/K+/Mg2+/Ca2+ exerted less effect on the adsorption of the aforementioned metal ions. The WO3–WS2/PPy exhibited higher selectivity toward Cd2+ than Ni2+. Along with, the WO3–WS2 decorated PPy based electrode showed a high specific surface area and support conductive networks, which synergistically improved charge storage capability. The WO3-WS2/PPy-based electrodes exhibit superior electrochemical performance with excellent rate capability, offering the high specific capacitance value of 624 F/g at 3 A/g current density and retaining capacitance stability of 81% after 5000 cycles in 1 M Na2SO4 electrolyte solution. The outcomes of this research infer that WO3-WS2/PPy is a promising candidate for wastewater treatment and high-performance energy storage applications.

Co-precipitation reaction: A facile strategy for designing hierarchical porous carbon nanosheets for EDLCs and zinc-ion hybrid supercapacitors

Hierarchical porous carbon is a valuable electrode material for electrochemical energy storage devices by virtue of its high specific surface area, excellent conductivity, and large pore volume. Herein, a simple, convenient and cheap self-made Fe-based template strategy is innovated to prepare hierarchical porous carbon employing coal chemical byproducts anthracene as carbon precursor, which is utilized as electrode materials of electrical double layer capacitors (EDLCs) and zinc ions hybrid supercapacitors (ZHSs). Benefiting from the high specific surface area (2085.1 m2 g−1), feasible micropore content (0.28 cm3 g−1), suitable oxygen content (11.57 at%) and two-dimensional nanosheet structure, the optimal sample delivered a high specific capacitance value of 183.5 F g−1 at 0.05 A/g and excellent rate capability (109.5 F g−1 at 20 A/g) for symmetric supercapacitor. Meanwhile, the as-fabricated ZHSs exhibited remarkable specific capacitance (181.67 mAh/g at 0.05 A/g), superior energy density (145.2 Wh kg−1), high power density (14.5 kW kg−1) and splendid cycling stability (∼91.25 % after 40,000 charge/discharge cycles at 2 A g−1). This work affords a new idea for the synthesis of template carbon using a feasible and low-cost co-precipitation reaction route and has great significance for the development of high-performance electrochemical energy storage device.

Electrochemical analysis of asymmetric supercapacitors based on BiCoO3@g-C3N4 nanocomposites.

Supercapacitors are gaining popularity these days because of their good cycle stability, superior specific capacitance, high power density, and energy density. Herein, we report the synthesis of bismuth cobalt oxide (BiCoO3) combined with graphitic carbon nitride (g-C3N4) by the hydrothermal method. The BiCoO3@g-C3N4 nanocomposite was well characterized using XRD, FE-SEM, FT-IR, and DRS-UV techniques. The supercapacitor properties of the BiCoO3@g-C3N4 nanocomposite were then studied using cyclic voltammetry, galvanic charging-discharging, and impedance spectroscopy techniques. Due to the synergistic effect, BiCoO3@g-C3N4 showed a high specific capacitance value of 341 F g-1 at a current density of 1 A g-1 and excellent retention of specific capacitance (98.82%) after 1000 cycles and a high power density of 1125 W kg-1. Using the impedance spectroscopy technique, the charge transfer resistance of BiCoO3, g-C3N4, and BiCoO3@g-C3N4 was measured. BiCoO3@g-C3N4 showed a low charge transfer resistance compared with BiCoO3 and g-C3N4. The asymmetric supercapacitor (ASC) device was prepared using activated carbon (negative side) and BiCoO3@g-C3N4 (positive side) electrodes. It showed a specific capacitance of 129 F g-1 at 1 A g-1, power density 2800 W kg-1 and energy density 35 W h kg-1. Finally, we conclude that, due to the high specific capacitance, good cycle retention, fast redox activity, and low charge transfer resistance BiCoO3@g-C3N4 is a good electrode material for energy storage applications.

Electrochemical performance of A-site substituted [formula omitted] for energy storage applications

In this work, a series of Ruddlesden popper oxide materials Sm1−xLaxSr1−xCaxNiO4−δ (x = 0.00, 0.05, 0.10, 0.15, and 0.20) were synthesized and their electrochemical behavior was investigated in 1 M KOH alkaline solution. Phase formation in all the samples is confirmed through XRD. SEM depicts the porous morphology of all the samples. FTIR confirms the presence of –OOH and –OH groups in several compositions. The Cyclic voltammetry curve of Sm0.90La0.10Sr0.90Ca0.10NiO4−δ and Sm0.80La0.20Sr0.80Ca0.20NiO4−δ indicates the presence of the combination of both pseudo-capacitance and electrochemical double-layer capacitance in these two electrodes. However, only the sample Sm0.90La0.10tSr0.90Ca0.10NiO4−δ sample satisfies the condition of the general power law for pseudo capacitance. This material also shows the highest value of specific capacitance (910.20 F/g) and electrochemical double-layer capacitance (238.25 mF/cm2) among all the samples. XPS analysis reveals that oxidation states of the Nickel and Oxygen play a crucial role for the better electrochemical performance of the electrode.

Designing a hierarchical structure of nickel-cobalt-sulfide decorated on electrospun N-doped carbon nanofiber as an efficient electrode material for hybrid supercapacitors

The intent of designing and exploring novel active electrode materials is to enhance the electrochemical performance of supercapacitors. Herein, a hierarchical structure of nickel-cobalt-sulfide nanostructures (NiCo2S4) decorated on the electrospun N-doped carbon nanofiber (CNF), NiCo2S4@CNF, is manipulated using a one-step and simple hydrothermal approach. The fabricated hierarchical structure of the NiCo2S4@CNF is featured by a large surface area and a high porosity that serve as ion diffusion channels. Therefore, it manifests high specific capacitance and specific capacity values of 377.2 C g−1 and 754.4 F g−1 at a current density of 1 A g−1, respectively. Furthermore, a NiCo2S4@CNF//CNF hybrid supercapacitor in which a positive electrode of NiCo2S4@CNF is assembled with a negative electrode of CNF to estimate the electrochemical performance of the NiCo2S4@CNF. As a result, the device has a superior energy density of 65.6 and 52.5 Wh kg−1 at a power density of 665 and 1313.8 W kg−1, respectively. Moreover, the device reveals good stability with capacitance retention of 72% after 3000 charge/discharge cycles. These outstanding results enable the designed hierarchical structure of the NiCo2S4@CNF to be a promising electrode material for supercapacitors (SCs) applications.