High Specific Capacitance Value Research Articles

Electrochemical properties of PEDOT/WO3 composite films for high performance supercapacitor application

Tungsten oxide was electrochemically deposited from a metastable acidic solution of isopolytungstate on glassy carbon electrodes coated by the films of a conducting polymer poly-3,4-ethylenedioxythiophene (PEDOT). The formation of PEDOT/WO3 composite films during electrochemical deposition of tungsten oxide into the polymer matrix was gravimetrically monitored by EQCM. The morphology of WO3 deposits was studied using SEM, TEM and EDX analysis, including element mapping and depth concentration profile of main elements. SEM and TEM images of PEDOT/WO3 composites show disperse distribution of WO3 precipitates in the porous matrix of PEDOT, possessing high surface area and pore volume, effective for charge transport. Electrochemical behavior of PEDOT/WO3 was investigated in 0.5 M H2SO4 by cyclic voltammetry, galvanostatic charge-discharge method and electrochemical impedance spectroscopy. The WO3 component in the obtained PEDOT/WO3 composite electrodes exhibited high specific capacitance of 689 F g−1 in the potential range −0.3–0.0 V. The work presents a simple approach for the synthesis of PEDOT/WO3 composites with high values of specific capacitance. The obtained results indicate that PEDOT/WO3 composite could be a promising electrode material for supercapacitor applications.

Facile synthesis of NFL-ZnWO4 for pseudocapacitor applications

In this report, NFL-ZnWO4 was synthesized by a hydrothermal route and investigated for application in supercapacitors for the first time. The physical and chemical characterizations of the prepared nanomaterial were analyzed by SEM, EDS, XRD and XPS, respectively. Supercapacitors study of CV, GCD and EIS revealed that NFL-ZnWO4 exhibits good electrochemical properties. The high specific capacitance value of 107.7 F g-1 was achieved at 5 mV s−1. These findings demonstrated that ZnWO4 could be a promising electrode material candidate and highly desirable for application of high property supercapacitors in the future.

Superbat: battery-like supercapacitor utilized by graphene foam and zinc oxide (ZnO) electrodes induced by structural defects.

The current work presents a hybrid type of energy storage device composed of both graphene foam and zinc oxide electrodes, which exhibits both the electrochemical performance of a supercapacitor with a relatively higher power density, and a battery with a relatively higher energy density as compared to each individual component as single devices. Te hybrid's improved performance was correlated to the defective structure of the electrodes. To enhance the electrochemical performance of supercapacitors, it is necessary to have a well-defined mass, shape, and surface area of electrode materials. Here, we present an original design of a mounting device that enabled precisely determining all the critical parameters of electrode materials for a particular mass and surface area. With the aid of our original setup, we produced a supercapacitor device that could also act as a battery due to its high energy density values, hence we named it as superbat. In this work, 3D graphene foam was used as the first electrode due to its large surface, while for the second electrode, ZnO nanocrystals were used due its defective structure. Paramagnetic resonance Raman and impedance spectroscopy were performed in order to understand the origin of the performance of the hybrid capacitor in more depth. In particular, we obtained a high specific capacitance value (C = 448 F g−1), which was exceptionally related not only to the quality of the synthesis but also the choice of electrode and electrolyte materials. Moreover, each component used in the construction of the hybrid supercapacitor also played a key role in to achieving high capacitance value. The results demonstrated the remarkable performance and stability of the superbat.

Аналіз способів зменшення шкідливих викидів суднових двигунів рециркуляцією відпрацьованих газів

Розвиток судноплавства на водних шляхах призвів до будівництва нового, сучасного флоту з потужними енергетичними установками. Масова експлуатація такого флоту супроводжується інтенсивним зростанням його впливу на навколишнє середовище. Один з найважливіших компонентів суспільного і економічного розвитку, який поглинає значну кількість ресурсів і надає серйозний вплив на природне середовище, є морський транспорт. В роботі проаналізовано можливість зменшення кількості шкідливих викидів судновими ДВЗ за рахунок системи рециркуляції відпрацьованих газів.

Nickel oxide nanoparticles supported onto oriented multi-walled carbon nanotube as electrodes for electrochemical capacitors

We report an electrode material for supercapacitors composed of nickel oxide (NiO) nanoparticles supported onto radially oriented multi-walled carbon nanotubes (CNTs) using a stainless-steel fine-mesh as the support (AISI:CNT-NiO). CNT scaffolds showed a turbostratic multi-walled structure with an interplanar spacing of 0.32 ± 0.02 nm and a diameter of ∼20–100 nm. NiO nanoparticles exhibited a diameter of ∼2–7 nm. X-ray data confirmed the presence of NiO in the scaffold. A large pseudocapacitive voltage range of 2.0 V was obtained in a 1.0 M Li2SO4 aqueous solution. The main contribution to the overall pseudocapacitance is due to the presence of reversible solid-state surface Faradaic reactions involving the Ni(II)/Ni(III) redox couple. High specific capacitance values of ∼1200 F g−1 at 5 A g−1 for the AISI:CNT-NiO electrode were extracted from galvanostatic discharge curves. Considering the contribution of negative voltages, the specific power and energy determined using cyclic voltammetry exhibited values of ∼140 Wh kg−1 and ∼9 W kg−1, respectively, at 0.02 V s−1. A specific capacitance of ∼1028 F g−1 was obtained at this scan rate. Even after 40,000 cycles carried out under galvanostatic conditions, the symmetric coin cell remained stable with a very high coulombic efficiency of ∼99%, which is a remarkable result. Also, we attributed to carbon nanotubes an extraordinary stability as electron drain on the current collector. The morphology factor analysis revealed that 19% of the electrochemically active surface area is confined to the inner surface regions of the porous nanostructured active layer. A low value of 0.15 mΩ g was extracted for the equivalent series resistance. New insights are presented concerning the true meaning of negative voltages for coin cells. Interesting findings regarding the porous nature of electrodes were elucidated using the impedance technique.

High-Performance Symmetrical Supercapacitor with a Combination of a ZIF-67/rGO Composite Electrode and a Redox Additive Electrolyte.

The synthesis of a highly porous composite of ZIF-67 and reduced graphene oxide (rGO) using a simple stirring approach is reported. The composite has been investigated as an electrode to be assembled in a supercapacitor. In the presence of an optimized redox additive electrolyte (RAE), that is, 0.2 M K3[Fe(CN)6] in 1 M Na2SO4, the ZIF-67/rGO composite electrode has combined the properties of improved conductivity, high specific surface area, and low resistance. The proposed composite electrode in the three-electrode system shows an ultrahigh specific capacitance of 1453 F g–1 at a current density of 4.5 A g–1 within a potential window of −0.1 to 0.5 V. Further, the ZIF-67/rGO composite electrode was used to fabricate a symmetrical supercapacitor whose operation in the presence of the RAE has delivered high values of specific capacitance (326 F g–1 at a current density of 3 A g–1) and energy density (25.5 W h kg–1 at a power density of 2.7 kW kg–1). The device could retain about 88% of its initial specific capacitance after 1000 repeated charge–discharge cycles. The practical usefulness of the device was also verified by combining two symmetrical supercapacitors in series and then lighting a white light-emitting diode (illumination for 3 min). This study, for the first time, reports the application of a ZIF-based composite (ZIF-67/rGO) in the presence of an RAE to design an efficient supercapacitor electrode. This proposed design is also scalable to a flexible symmetric device delivering high values of specific capacitance and energy density.

Synthesis and characterization of activated carbon from the biomass of Saccharum bengalense for electrochemical supercapacitors

Abstract Low cost and very simple activation method (ZnCl2 as activating agent) is used for the synthesis of activated carbon derived from the biomass of Saccharum bengalense (S. bengalense) leaves. The S. bengalense derived activated carbon (SbAC) as the electrode material in Electric Double Layer Capacitors (EDLCs) is reported for the first time. The structural, surface morphological study and vibrational response of the SbAC are characterized by using X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy, and Brunauer-Emmett-Teller (BET) surface area. Electrochemical studies indicate that the SbAC delivers the maximum specific capacitance of 102.6 F g−1at scan rate of 2 mV/s in aqueous electrolyte (1 M Li2SO4) for 1.6 V operating voltage. This high value of specific capacitance is credited to its high specific surface area (2090 m2 g−1) and pore volume of 0.281 cm3 g−1. The SbAC exhibits good rate capability with an excellent charging/discharging cycle stability in aqueous electrolyte (1 M Li2SO4) during 120,000 cycles. The results indicate that SbAC shows good electrochemical properties to be used for energy storage applications in future.

New Fe₂O₃-Clay@C Nanocomposite Anodes for Li-Ion Batteries Obtained by Facile Hydrothermal Processes.

New iron-oxide-based anodes are prepared by an environmentally-friendly and low-cost route. The analysis of the composition, structure, and microstructure of the samples reveals the presence of a major hematite phase, which is accompanied by a certain concentration of an oxyhydroxide phase, which can act as a “lithium-reservoir”. By using sodium alginate as a binder, the synthesized anodes display superior electrochemical response, i.e., high specific capacity values and high stability, not only versus Li but also versus a high voltage cathode in a full cell. From these bare materials, clay-supported anodes are further obtained using sepiolite and bentonite natural silicates. The electrochemical performance of such composites is improved, especially for the sepiolite-containing one treated at 400 °C. The thermal treatment at this temperature provides the optimal conditions for a synergic nano-architecture to develop between the clay and the hematite nanoparticles. High capacity values of ~2500 mA h g−1 after 30 cycles at 1 A g−1 and retentions close to 92% are obtained. Moreover, after 450 cycles at 2 A g−1 current rate, this composite electrode displays values as high as ~700 mA h g−1. These results are interpreted taking into account the interactions between the iron oxide nanoparticles and the sepiolite surface through hydrogen bonds. The electrochemical performance is not only dependent on the oxidation state and particle morphology, but the composition is revealed as a key feature.

Ru and Os based new electrode for electrochemical flow supercapacitors

Here, we propose by means of a scalable and one-step approach, an efficient procedure for the synthesis of a multifunctional RuOsOx/G supercapacitor electrode material. Firstly, the synthesized material was extensively characterized: XRD, SEM and TEM images showed the existence of a quaternary nanostructure comprising RuO2 and OsO2 and metal inclusions, supported on graphene. Secondly, the capacitance performance of the synthesized sample was tested through cyclic voltammetry (CV) and galvanostatic charge and discharge (GCD) tests in a slurry flowable electrode configuration. RuOsOx/G shows very high specific capacitance (Csp) values: 729 F/g at 1 A/g and 718 F/g at 10 mV/s. Csp remains 627.3 F/g at 200 mV/s, therefore proving an excellent capacitance retention (∼90%). The capacitance evaluated on the bases of the two oxides weight is ∼1300 F/g, which is one of the highest Csp values among the reported in literature thus far. Moreover, the material exhibits a remarkable long-term stability: 98.5% of the initial capacitance was retained after 25,000 cycles at 20 A/g and the Coulombic efficiency is equal to 100%.

Fluorine-doped anatase for improved supercapacitor electrode

Anatase is an attractive supercapacitor material as it is widely available, non-toxic, stable over a wide potential window, and has a high theoretical value of specific capacitance, but the experimental value is still low. Here, we show that HF treatment leads to simultaneous nanostructuring and fluorine doping of anatase. Structural characterizations show a substantial reduction in the particle size and an order of magnitude increase in the surface area without any change in the distribution of the crystal facets of anatase. Material characterizations show that fluorine doping leads to the creation of oxygen vacancies as well as the Ti3+ states. Electrochemical characterizations show that these defects increase electronic charge carrier density (9×1019 cm−3) and local conductivity of the doped anatase by an order of magnitude compared to the pristine anatase (7.68×1018 cm−3). As a result of this, doped anatase shows three times (236 Fg−1) higher specific capacitance than the pristine one and its rate capability is also better. Doped anatase also has good cycling stability with a minimum decrease in the specific capacitance through 10000 charge/discharge cycles.

Morphology and performance of CoOOH films synthesized via electrochemical oxidation: substrate effects

In the present work, CoOOH films are synthesized from the electrochemical oxidation of α-Co(OH)2 as precursor. The substrate influences on the material electrochemical properties are studied. The samples are structural and morphologically characterized using techniques of X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy techniques are used for the electrochemical characterization. The films deposited on steel substrate grew in the vertical hexagonal platelet form. Meanwhile, films on Ti plate presented morphology in agglomerated sphere form. After electrochemical oxidation, the film initial morphology is maintained. The films deposited on steel plate have a structure which favors charge storage showing a high specific capacity value (110.92 mA h g−1) and cyclic stability of 92% after 1000 cycles. Finally, the relaxation time constant value calculated was 5.6 s. This fact is making this material as a possible good candidate for application as electrode material or additive for other materials, in energy storage devices.

CaO impregnated highly porous honeycomb activated carbon from agriculture waste: symmetrical supercapacitor study

This study presents the electrochemical studies of activated carbon prepared from palm kernel shell (ACPKS), with CaO impregnation. The CaO is obtained from chicken eggshell waste to produce CaO/ACPKS, which shows highly porous honeycomb structure with homogeneous distribution of CaO nanoparticles (30–50 nm in size). The prepared materials are evaluated as supercapacitor electrodes by testing their electrochemical characteristics. A high specific capacitance value of 222 F g−1 at 0.025 A g−1 is obtained for CaO/ACPKS, which is around three times higher than that for ACPKS (76 F g−1). In addition, electrochemical impedance data show lower impedance for CaO/ACPKS. Lastly, a practical symmetrical supercapacitor is fabricated by CaO/ACPKS and its performance is discussed.

Метод рециркуляції відпрацьованих газів суднових дизелів для зме-ншення їх токсичності

В даний час має місце інтенсивне посилення норм на токсичні викиди відпрацьованих газів суднових дизелів при плаванні суден в прибережних морських районах і на внутрішніх водних шляхах. Постійне зростання числа суден призводить до збільшення об’єму палива, що спалюється ними, а отже до збільшення викидів токсичних компонентів з відпрацьованими газами. В роботі проаналізовано зниження шкідливих викидів судновими дизелями за рахунок методу рециркуляції відпрацьованих газів.

Investigation of electrochemical capacitance of 18k nanoporous current collector incorporated MnO2

This paper deals with the fabrication of super capacitor electrode material employing a facile etching process followed by electrodeposition. Nanoporous gold current collector has been fabricated by chemically dealloying commercially available 18k gold having a composition of 74% Au, 24% Cu and 2% Ag, with dilute HNO3 solution. Electrochemically deposited MnO2 over the prepared porous Au electrode exhibits a very high specific capacitance value of 670 Fg-1 which is about 1.65 times greater than that of MnO2 coated over unetched Au electrode (407 Fg-1). Etched and unetched MnO2 coated electrode materials are characterized using XRD, XPS, FESEM with EDAX and AFM. Electrochemical characterization of the obtained hybrid material is evaluated by running several cyclic voltagramms using electrochemical workstation. In contrast to the MnO2 coated unetched Au hybrid electrode system, nanoporous AuMnO2 electrode displays higher phase angle (79°) and lower time constant (2 ms) derived from the bode plot suggesting a better capacitance value. The high specific capacitances offered with good charge/discharge rates at a potential window of 0–0.8 V, in the scan rate of 100 mV/s for 1000 cycles, exhibiting high-energy storage density of 32.56 wh/kg and 53.6 wh/kg and power density of 366 w/kg and 603 w/kg for un-etched and etched electrodes respectively.

A flexible supercapacitor consisting of activated carbon nanofiber and carbon nanofiber/potassium-pre-intercalated manganese oxide

Potassium-pre-intercalated δ-phase MnO2 is uniformly grown on carbon nanofibers for the positive electrode of asymmetric supercapacitors. An electrospun CNF is chemically activated with KOH at 800 °C for the negative electrode, showing ideal capacitive behavior. The crystallinity of MnO2 is significantly reduced by the pre-intercalation of K ions into its layered structure. This textural characteristic is beneficial to the K+ diffusion into/out the interlayer structure, leading to effective utilization of the electroactive material of KxMnO2. This unique composite electrode provides both ideal pseudo-capacitive behavior from KxMnO2 and excellent electric conductivity from the CNF network, exhibiting a fairly high specific capacitance value of 279 F g-1 at 1 A g−1 with ca. 82.3% capacitance retention from 1 to 32 A g−1. A flexible ASC consisting of the positive KxMnO2@CNF electrode, a paper separator, and the negative ACNF electrode is successfully assembled. This cell shows superior ASC performances: a high cell voltage between 0 and 2 V, excellent capacitance retention (10,000 cycles with 10% decay), and simultaneously reaching high specific energy and power of 21.1 Wh kg−1 and 9.5 kW kg−1. The charge storage behavior of this cell without bending and with a bending angle of 90° shows no apparent difference, demonstrating its potential in the next-generation flexible energy storage devices.

Photocatalytic, magnetic, and electrochemical properties of La doped BiFeO3 nanoparticles

We successfully prepared La1−xBixFeO3 (LxB1−xFO, x = 0.01–0.1) nanoparticles using a sol-gel technique, and studied their photocatalytic, magnetic, and electrochemical properties. Structural refinement studies of the prepared nanoparticles revealed a gradual structural transition from rhombohedral to orthorhombic. The average grain size was observed to decrease with increasing the concentration of La. The photocatalytic degradation of Rhodamine B (RhB) in the presence of the prepared nanoparticles was studied under visible light irradiation. The L0.06B0.94FO nanoparticles showed higher degradation efficiency compared to pure BiFeO3 (BFO) nanoparticles. Magnetic studies showed that La doping improved the magnetization of BFO due to the reduction in grain size and destruction of cycloid coupling of spins. Higher specific capacitance values were obtained for La doped BFO (LBFO) nanoparticles compared to BFO nanoparticles. A maximum specific capacitance of 219 F g−1 was obtained at a current density of 1 A g−1 for LBFO nanoparticles.

A high performance symmetrical supercapacitor based on NiCo2O4 nanowires on thin film carbon layer

Here we proposed novel NiCo2O4 nanowires on carbon black layer that used as a superior electrode for supercapacitors, with an excellent pseudocapacitive performance. The NiCo2O4 nanowires-based electrode provide high values of specific capacitance of 3.31 F/cm2 corresponding to the current densities of 5 mA/cm2. The symmetrical supercapacitor based on NiCo2O4 nanowires-based electrode have a high areal specific capacitance of 42.6 mF/cm2 corresponding to the current densities of 0.5 mA/cm2. It exhibited good cycling life that the specific capacitance maintained with no decrease during 50000 cycles. Our work can be applied in mass applications of high-capacitance energy-storage supercapacitors.

Fabrication of Amorphous Indium–Gallium– Zinc–Oxide Thin-Film Transistor on Flexible Substrate Using a Polymer Electrolyte as Gate Dielectric

We have fabricated a flexible thin-film transistor (TFT) with relevant high performance indices using polymer electrolyte as gate dielectric and amorphous indium–gallium–zinc–oxide (a-IGZO) (a-InGaZn2O5) as a channel on polyimide Kapton tape. Low temperature ( $\approx 100~^{\circ }\text{C}$ –120 °C) prepared a-IGZO, showed n-channel device characteristic, and operated in the enhancement mode with a high saturation mobility of 42 cm2/ $\text {V}\cdot \text {s}$ , good ON/OFF ratio of ~105, low threshold voltage of ~0.7 V, and low subthreshold swing of ~175mV/decade. The improvements of the performance indices arise due to influence high value of specific gate capacitance of polymer electrolyte. The gate bias stress test of the flexible TFT showed the stable electrical characteristics.

High-performance solid state supercapacitors assembling graphene interconnected networks in porous silicon electrode by electrochemical methods using 2,6-dihydroxynaphthalen

The challenge for conformal modification of the ultra-high internal surface of nanoporous silicon was tackled by electrochemical polymerisation of 2,6-dihydroxynaphthalene using cyclic voltammetry or potentiometry and, notably, after the thermal treatment (800 °C, N2, 4 h) an assembly of interconnected networks of graphene strongly adhering to nanoporous silicon matrix resulted. Herein we demonstrate the achievement of an easy scalable technology for solid state supercapacitors on silicon, with excellent electrochemical properties. Accordingly, our symmetric supercapacitors (SSC) showed remarkable performance characteristics, comparable to many of the best high-power and/or high-energy carbon-based supercapacitors, their figures of merit matching under battery-like supercapacitor behaviour. Furthermore, the devices displayed high specific capacity values along with enhanced capacity retention even at ultra-high rates for voltage sweep, 5 V/s, or discharge current density, 100 A/g, respectively. The cycling stability tests performed at relatively high discharge current density of 10 A/g indicated good capacity retention, with a superior performance demonstrated for the electrodes obtained under cyclic voltammetry approach, which may be ascribed on the one hand to a better coverage of the porous silicon substrate and, on the other hand, to an improved resilience of the hybrid electrode to pore clogging.

Microwave-assisted synthesis of Ru and Ce doped tungsten oxide for supercapacitor electrodes

Ruthenium (Ru) and cerium (Ce) doped tungsten oxide (WO3) were successfully synthesized at various concentration (1–5 wt.%) by microwave irradiation method without adding any surfactant and studied as a supercapacitor electrode material for the first time. The effect of Ru and Ce on structural and morphological properties were studied systematically by using powder X-ray diffraction (XRD), thermogravimetry (TG)-differential thermal analysis (DTA), scanning electron microscopy (SEM) and tunneling electron microscopy (TEM). Powder XRD analyses reveal the formation of orthorhombic structure for the as-synthesized pure and doped WO3. Annealing at 500 °C modifies the structure of the as-synthesized materials from orthorhombic to monoclinic. TG-DTA shows the elimination of water at around 170 °C which confirms the structural change of orthorhombic to monoclinic. TEM images shows that the doping in WO3 affects the morphology, changing form hexagonal shape to elongated spherical shape and flake-like nanoclusters in Ru and Ce doped WO3, respectively. The electrochemical measurements of cyclic voltammetry, galvanostatic charge–discharge and impedance were performed in a three-electrode configuration to assess the electrochemical performances of the synthesized materials for supercapacitor applications. Among all the doping, 2 wt.% Ce doped WO3 shows a high specific capacitance value of 52 F g−1 at a current density of 0.1 A g−1. The energy density is found to be 5.49 W h Kg−1 for W0.98Ru0.02O3 and 7.22 W h Kg−1 for W0.98Ce0.02O3 at a power density of 50.08 W Kg−1 and 49.22 W Kg− 1, respectively.