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1.
Co3O4 nanoplate/graphene sheet composites were prepared through a two-step synthetic method. The composite material as prepared was characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The platelet-like morphology of Co3O4 leads to a layer-by-layer-assembled structure of the composites and a good dispersion of Co3O4 nanoplates on the surface of graphene sheets. The electrochemical characteristics indicate that the specific capacitance of the composites is 337.8 F?g?1 in comparison with the specific capacitance of 204.4 F?g?1 without graphene sheets. Meanwhile, the composites have an excellent rate capability and cycle performance. The results show that the unique microstructure of the composites enhances the electrochemical capacitive performance of Co3O4 nanoplates due to the three-dimensional network of graphene sheets for electron transport increasing electric conductivity of the electrode and providing unobstructed pathways for ionic transport during the electrochemical reaction.  相似文献   

2.
Present investigation reports, spray pyrolytic deposition of Mn: Co3O4 thin films onto the stainless steel by spray pyrolysis, at the deposition temperature 573 ± 2 K via aqueous route. Prepared electrodes were characterized structurally and morphologically by means of XRD and SEM. Also optical and electrochemical characterizations were carried out in depth. Structural characterization confirms face centered cubic and tetragonal body centered crystal structures for Co3O4 and Mn3O4 respectively. The rough granular morphology is observed form SEM. Electrochemical study reveals the pseudo capacitive as well as double layer behavior with optimum specific capacitance 485.29 F/g at the scan rate 1 mV/s in 1 M KOH electrolyte. Specific energy, specific power and columbic efficiency were calculated using chronopotentiometric technique. Electrochemical impedance spectroscopy was carried out in the frequency range 1 mHz–1 MHz. Randles equivalent circuit parameters associated with the operative cell are reported.  相似文献   

3.
The fabrication of high performance supercapacitor electrodes has been greatly investigated for future high power storage applications. In this present work, chromium oxide-cobalt oxide based nanocomposite (Cr2O3–Co3O4 NC) was synthesized using the hydrothermal approach. Moreover, the cyclic voltammetry (CV) study reveals the Cr2O3–Co3O4 NC delivers a high specific capacitance of 619.4 F/g at 10 mV/s. The electrochemical impedance spectra (EIS) of Cr2O3–Co3O4 NC possess the solution resistance (Rs) and charge transfer resistance (Rct) of 0.68 Ω and 0.03 Ω respectively. The Galvanostatic charge-discharge (GCD) analysis demonstrated the prolonged charge-discharge time and good rate capability of the Cr2O3–Co3O4 NC. The cyclic stability of Cr2O3–Co3O4 NC delivers superior capacitive retention of 83% even after 2000 cycles. The asymmetric supercapacitor (ASC) device based on Cr2O3–Co3O4//AC yielded an energy density of 4.3 Wh/kg at the corresponding power density of 200 W/kg. Furthermore, the ASC delivers superior cyclic stability of 74.8% even after 1000 consecutive charge-discharge cycles.  相似文献   

4.
The development of smart structured cathode materials for supercapacitors (SCs) has sparked tremendous interest. However, the appropriate design to achieve high capacitance and energy density-based cathode materials remains a major problem for energy storage systems. This article describes the effective synthesis of self-supported 3D micro-flowers composed of ultrathin nanowires array of Co3O4 on Ni foam (NF) using hydrothermal conditions (Co3O4@NF). The mesoporous Co3O4@NF with a high surface area, providing a rich active state for the Faraday redox reaction and increasing the diffusion rate of the electrolyte ions. The optimized Co3O4@NF-16h electrode exhibited supreme electrochemical performance by delivering a high specific capacitance of 1878, (1127) and 1200 (720 C g−1) F g−1 at 1.0 and 20 A g−1, respectively. The Co3O4@NF electrode retained good capacitance stability of 91% over 10000 cycles at 20 A g−1 with excellent rate-performance of 67% at 20 folded high current values. The obtained results for the Co3O4@NF electrode are presented the enhanced pseudocapacitive performance, indicating the substantial potential for high-performance supercapacitor applications.  相似文献   

5.
In this study, a symmetric electrochemical capacitor was fabricated by adopting a lithium iron phosphate (LiFePO4)-activated carbon (AC) composite as the core electrode material in 1.0 M Na2SO3 and 1.0 M Li2SO4 aqueous electrolyte solutions. The composite electrodes were prepared via a facile mechanical mixing process. The structural properties of the nanocomposite electrodes were characterised by scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) analysis. The electrochemical performances of the prepared composite electrode were studied using cyclic voltammetry (CV), galvanostatic charge–discharge (CD) and electrochemical impedance spectroscopy (EIS). The experimental results reveal that a maximum specific capacitance of 112.41 F/g was obtained a 40 wt% LiFePO4 loading on an AC electrode compared with that of a pure AC electrode (76.24 F/g) in 1 M Na2SO3. The improvement in the capacitive performance of the 40 wt% LiFePO4–AC composite electrode is believed to be attributed to the contribution of the synergistic effect of the electric double layer capacitance (EDLC) of the AC electrode and pseudocapacitance via the intercalation/extraction of H+, OH, Na+ and SO32− and Li+ ions in LiFePO4 lattices. In contrast, it appears that the incorporation of LiFePO4 into AC electrodes does not increase the charge storage capability when Li2SO4 is used as the electrolyte. This behaviour can be explained by the fact that the electrolyte system containing SO42− only exhibits EDLC in the Fe-based electrodes. Additionally, Li+ ions that have lower conductivity and mobility may lead to poorer charge storage capability compared to Na+ ions. Overall, the results reveal that the AC composite electrodes with 40 wt% LiFePO4 loading on a Na2SO3 neutral electrolyte exhibit high cycling stability and reversibility and thus display great potential for electrochemical capacitor applications.  相似文献   

6.
A reduced graphene oxide/multiwalled carbon nanotube (RGO/MWCNT) hybrid sandwiched film with different MWCNTs content was prepared by vacuum-assisted self-assembly from a complex dispersion of graphene oxide (GO) and MWCNTs followed by heat-treating at 200 °C for 1 h in a vacuum oven to reduce the GO into RGO. The free-standing RGO/MWCNT hybrid sandwiched film before heat-treatment showed a layered structure with an entangled network of MWCNTs sandwiched between the GO sheets. This unique structure not merely contribute to remove the oxygen-containing groups in GO during the heat-treatment, but also decrease the defects for electron transfer between RGO layers, which enhances the electrochemical capacitive performances of graphene-based films. A specific capacitance up to 379 F/g was achieved based on RGO/MWCNT with 30 % MWCNTs mass fraction at 0.1 A/g in a 6 M KOH electrolyte. The excellent performance of RGO/MWCNT hybrid sandwiched film signifies the importance of controlling the surface chemistry and sandwiched nanostructure of graphene-based materials.  相似文献   

7.
A series of LiNi1/3Co1/3Mn1/3O2/LiFePO4 composite cathodes with the LiFePO4 mass content ranging from 10 to 30 wt% were prepared by ball milling in order to combine the merits of layered LiNi1/3Co1/3Mn1/3O2 and olivine LiFePO4. The structure and morphology of the samples were characterized by X-ray diffraction and scanning electron microscope. The composite cathodes exhibited improved electrochemical performance compared with pristine LiNi1/3Co1/3Mn1/3O2. Among all the composite cathodes, the one with 20 wt% of LiFePO4 showed the best electrochemical performance in terms of discharge capacity, cycle stability, and rate capability. Electrochemical impedance spectroscopy showed that mixing of LiFePO4 in LiNi1/3Co1/3Mn1/3O2 decreased the internal resistance of the electrode, retarded the formation of SEI film, and facilitated the charge transfer reaction. Differential scanning calorimetry showed that the composite cathode had better thermal stability than pristine LiNi1/3Co1/3Mn1/3O2.  相似文献   

8.
Commercial application of supercapacitors (SCs) requires high mass loading electrodes simultaneously with high energy density and long cycle life. Herein, we have reported a ternary multi-walled carbon nanotube (MWCNT)/MnO2/reduced graphene oxide (rGO) nanocomposite for SCs with commercial-level mass loadings. The ternary nanocomposite was synthesized using a facile ultrasound-assisted one-pot method. The symmetric SC fabricated with ternary MWCNT/MnO2/rGO nanocomposite demonstrated marked enhancement in capacitive performance as compared to those with binary nanocomposites (MnO2/rGO and MnO2/MWCNT). The synergistic effect from simultaneous growth of MnO2 on the graphene and MWCNTs under ultrasonic irradiation resulted in the formation of a porous ternary structure with efficient ion diffusion channels and high electrochemically active surface area. The symmetric SC with commercial-level mass loading electrodes (∼12 mg cm−2) offered a high specific capacitance (314.6 F g−1) and energy density (21.1 W h kg−1 at 150 W kg−1) at a wide operating voltage of 1.5 V. Moreover, the SC exhibits no loss of capacitance after 5000 charge−discharge cycles showcasing excellent cycle life.  相似文献   

9.
In this work, air-oxidized multi-walled carbon nanotube (MWCNT) electrodes have been prepared from catalytically grown MWCNTs of high purity and narrow diameter distribution. The experimental results show that air-oxidation modifies the intrinsic structure of individual MWCNTs and a little improves the dispersity of the MWCNTs. The specific capacitances of the electrodes in electric double layer capacitors (EDLCs) based on oxidized MWCNTs are obviously improved through air-oxidation. The specific capacitance of 50 F/g is obtained in the air-oxidized MWCNTs at 600 °C on a single cell device with 35 wt% H2SO4 as an electrolyte. This is probably increased BET specific surface area and mesopore volume of the oxidized MWCNT electrode materials of EDLCs. These properties are, therefore highly desirable for the development of electrochemical capacitors with high power and long cycle life.  相似文献   

10.
Nanoporous/cracked structures of cobalt oxide (Co3O4) electrodes were successfully fabricated by electroplating of zinc–cobalt onto previously formed TiO2 nanotubes by anodizing of titanium, leaching of zinc in a concentrated alkaline solution and followed by drying and annealing at 400 °C. The structure and morphology of the obtained Co3O4 electrodes were characterized by X-ray diffraction, EDX analysis and scanning electron microscopy. The results showed that the obtained Co3O4 electrodes were composed of the nanoporous/cracked structures with an average pore size of about 100 nm. The electrochemical capacitive behaviors of the nanoporous Co3O4 electrodes were investigated by cyclic voltammetry, galvanostatic charge–discharge studies and electrochemical impedance spectroscopy in 1 M NaOH solution. The electrochemical data demonstrated that the electrodes display good capacitive behavior with a specific capacitance of 430 F g?1 at a current density of 1.0 A g?1 and specific capacitance retention of ca. 80 % after 10 days of being used in electrochemical experiments, indicating to be promising electroactive materials for supercapacitors. Furthermore, in comparison with electrodes prepared by simple cathodic deposition of cobalt onto TiO2 nanotubes(without dealloying procedure), the impedance studies showed improved performances likely due to nanoporous/cracked structures of electrodes fabricated by dealloying of zinc, which provide fast ion and electron transfer routes and large reaction surface area with the ensued fast reaction kinetics.  相似文献   

11.
A new type of gas sensing material based on metal oxide modification multi wall carbon nanotube (MO/MWCNT) composites is presented since the interface between the composites enhance the carrier density so as to improve the gas sensitivity. Three kinds of MO/MWCNT composite materials, such as ZnO/MWCNT, SnO2/MWCNT and TiO2/MWCNT, have been acquired in situ growth using catalytic pyrolysis method. The MO nano particles have decorated on side of MWCNTs, whereas the introduction of SnO2 nano particles makes part of MWCNT showing two-dimensional form of carbon nano-wall structure. Among four kinds of cathode of ZnO/MWCNTs, SnO2/MWCNTs, TiO2/MWCNTs and pure MWCNT composite film, TiO2/MWCNTs composite has the lowest threshold electric field required to draw current of 12 μA has been found to be ∼1.2 V/μm, and also TiO2/MWCNTs composite has the highest sensitivity of 16% to ethanol. The TiO2/MWCNTs composite is superior to the others both in vacuum electron transportation and gas sensitivity.  相似文献   

12.
Abstract

High performance electrodes for supercapacitor usually are achieved by compositing conductive and redox materials, the former such as multi-walled carbon nanotubes (MWCNTs), graphene, etc., provide the electrical double-layer capacitances that far less than pseudo-capacitances of the later (metal oxide, polyaniline, and so on). Here, carbonaceous composite electrode of MWCNTs and the redox electrolyte are combined into an electrochemical system for high synergetic effect of capacitance. MWCNT is activated by acid treatment and its structures are characterized by scanning electron microscope, X-ray diffraction, and Infrared spectroscopy analyses. The electrochemical measurements of resultant electrodes showed an excellent synergetic effect. The acid-activated MWCNTs electrode exhibited the maximum specific capacitance of 682 F/g in 0.2 M KI redox electrolytes, which is about 2–20 times larger than MWCNTs and its composite electrode in universal electrolyte without KI.  相似文献   

13.
《Current Applied Physics》2018,18(11):1399-1402
Nanorod films of cobalt oxide (Co3O4) have been grown by a unique oblique angle deposition (OAD) technique in an e-beam evaporator for supercapacitor electrode applications. This technique offers a non-chemical route to achieve large aspect ratio nanorods. The fabricated electrodes at OAD 80° exhibited a specific capacitance of 2875 F/g. The electrochemically active surface area was 1397 cm−2, estimated from the non-Faradaic capacitive current region. Peak energy and power densities obtained for Co3O4 nanorods were 57.7 Wh/Kg and 9.5 kW/kg, respectively. The Co3O4 nanorod electrode showed a good endurance of 2000 charge-discharge cycles with 62% retention. The OAD approach for fabricating supercapacitor nanostructured electrodes can be exploited for the fabrication of a broad range of metal oxide materials.  相似文献   

14.
Uniform and adherent cobalt oxide thin films have been deposited on glass substrates from aqueous cobalt chloride solution, using the solution spray pyrolysis technique. Their structural, optical and electrical properties were investigated by means of X-ray diffraction (XRD), scanning electron micrograph (SEM), optical absorption and electrical resistivity measurements. Along with this, to propose Co3O4 for possible application in energy storage devices, its electrochemical supercapacitor properties have been studied in aqueous KOH electrolyte. The structural analysis from XRD pattern showed the oriented growth of Co3O4 of cubic structure. The surface morphological studies from scanning electron micrographs revealed the nanocrystalline grains alongwith some overgrown clusters of cobalt oxide. The optical studies showed direct and indirect band gaps of 2.10 and 1.60 eV, respectively. The electrical resistivity measurement of cobalt oxide films depicted a semiconducting behavior with the room temperature electrical resistivity of the order of 1.5 × 103 Ω cm. The supercapacitor properties depicted that spray-deposited Co3O4 film is capable of exhibiting specific capacitance of 74 F/g.  相似文献   

15.
Stable electrochemical capacitive properties of chemically grown cadmium oxide film electrode composed of micron-sized discrete crystals in 1 M Na2SO4 electrolyte with a specific capacitance of 1190 mF/g studied over 1000 cycles are reported. Structural and morphological characterizations of micron-sized discrete CdO crystals have been carried out using power X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. Electrochemical capacitive properties of micron-sized CdO discrete crystals on tin-doped indium oxide electrode have been investigated using cyclic voltammetry and chronopotentiometry.  相似文献   

16.
High-density polyethylene (HDPE) composites reinforced with multiwalled carbon nanotubes (MWCNTs) and nano-silicon dioxide (SiO2) fillers were evaluated for flame retardancy and thermal properties for cable and wire applications. In this study, the filler percentages of MWCNT and nano-SiO2 have varied from 0 to 5 wt% in HDPE composite with polyethylene-grafted glycidyl methacrylate compatibilizer and 3-aminopropyl triethoxy silane coupling agent. Addition of MWCNT’s and nano-SiO2 to the HDPE composite is observed to enhance the limiting oxygen index and char formation. Cone calorimeter results also show a 53% reduction in the peak heat release rate of the HDPE composite with 5 wt% of MWCNT. The existence of synergism between the uniformly dispersed MWCNT and nano-SiO2 has been verified using Finite Element Method (FEM)-based thermal simulations.  相似文献   

17.
《Solid State Ionics》2006,177(35-36):3187-3191
The electrochemical properties of geometrically well-defined Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) microelectrodes have been investigated by impedance spectroscopy. The microelectrodes of 20–100 μm diameter and 100 nm thickness were prepared by pulsed laser deposition (PLD), photolithography and argon ion beam etching. The oxygen reduction reaction at these model electrodes is limited by interfacial processes, i.e. by the oxygen surface exchange and/or by the transfer of oxide ions across the electrode/electrolyte boundary, whereas the resistance associated with the transport of oxide ions through the bulk of the thin film electrode is negligible. The experiments revealed an extremely low absolute value of the electrochemical surface exchange resistance of only 0.09 (± 0.03) Ω cm2 at 750 °C in air, which is more than a factor of 50 lower than the corresponding value measured for La0.6Sr0.4Co0.8Fe0.2O3−δ (LSCF) microelectrodes of the same geometry. The dependence of this and other electrochemical quantities such as the chemical bulk capacitance or the BSCF/YSZ interfacial resistance on temperature has been studied between 500 and 750 °C.  相似文献   

18.
In this work, two different types of Co3O4 nano-crystals were synthesized by (i) conventional direct solid state thermolysis of cobalt terephthalate metal-organic framework (MOF-71) and (ii) new indirect solid state thermolysis of Co(OH)2 derived by alkaline aqueous treatment of MOF-71. The products were then characterized by X-ray diffraction technique (XRD), Fourier transforms infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Reflection electron energy loss spectroscopy (REELS), Brunauer, Emmett, and Teller (BET), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) techniques. By REELS analysis the energy band gap of MOF-71 was determined to be 3.7 eV. Further, electrochemical performance of each Co3O4 nanostructure was studied by the cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) in a three-electrode system in KOH electrolyte. An asymmetric supercapacitor was fabricated using indirect Co3O4 nanoparticles as cathode and electrochemically reduced graphene oxide as anode, and the electrochemical properties were studied and showed a high energy density of 13.51 Wh kg−1 along with a power density of 9775 W kg−1 and good cycling stability with capacitance retention rate of 85% after 2000 cycles.  相似文献   

19.
Effect of micron-sized MgO particles dispersion on poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF–HFP) based magnesium-ion (Mg2+) conducting gel polymer electrolyte has been studied using various electrical and electrochemical techniques. The composite gel films are free-standing and flexible with enough mechanical strength. The optimized composition with 10 wt% MgO particles offers a maximum electrical conductivity of ∼6×10−3 S cm−1 at room temperature (∼25°C). The Mg2+ ion conduction in gel film is confirmed from cyclic voltammetry, impedance spectroscopy and transport number measurements. The applicability of the composite gel electrolyte to a rechargeable battery system has been examined by fabricating a prototype cell consisting of Mg (or Mg–MWCNT composite) and V2O5 as negative and positive electrodes, respectively. The rechargeability of the cell has been improved, when Mg metal was substituted by Mg–MWCNT composite as negative electrode.  相似文献   

20.
The main challenge of low infrared emissivity coatings based on aluminum flake lies in finding an efficient method to synthesize the composite pigment with low infrared emissivity and low lightness simultaneously. In this work, we overcome this constraint to some extent, synthesizing a novel Al/Co3O4 magnetic composite pigments with low infrared emissivity and low lightness by thermal cracking and hot flowing method. The results show that the covering area of Co3O4 on the aluminum flake can be tuned by the amount of CoCO3 adding in precursor and the reaction temperature of hot flowing, both of which pay a key factor on the VIS and IR spectral reflectance and magnetic properties. The magnetic Al/Co3O4 composite pigments with low lightness and low infrared emissivity can be obtained at 130 °C for 24 h in hot flowing liquid. The lightness L1 can be decreased to 69.2, however the infrared emissivity (8–14 μm) is also low to 0.45. Compared with the single Al flakes, Al/Co3O4 magnetic composite pigments present stronger magnetic properties. Therefore, the Al/Co3O4 magnetic composite pigments have offered new choice for the pigments of low infrared emissivity coatings.  相似文献   

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