Capacitance Of Co Research Articles

Cattail spike-like Co(OH)F@Co3O4 nanoarrays for high-performance supercapacitors

Cattail spike-like Co(OH)F@Co3O4 nanoporous arrays were successfully prepared on nickel foam by hydrothermal method and calcination treatment. The Co(OH)F@Co3O4 nanoarrays, combining the advantages of the Co(OH)F and the Co3O4, exhibit ultrahigh structural stability and excellent electrochemical performance. The specific capacitance of Co(OH)F@Co3O4 is 543F g−1 at the current density of 1A g−1 and could maintain 88.34 % specific capacitance after 5000 cycles at 10 A g−1. Moreover, a two-electrode system assembled by Co(OH)F@Co3O4 and reduced graphene oxide exhibits a peak energy density of 30.155 Wh kg−1 at the power density of 800 W kg−1 and possesses an excellent cycling retention of 84.88 % after 5000 cycles at 10A g−1. These results indicate that the prepared Co(OH)F@Co3O4 composite is a promising positive electrode material for supercapacitors.

Co(OH)F@CoP/CC core-shell nanoarrays for high-performance supercapacitors

The transition metal phosphides have drawn wide attention as positive material used in supercapacitors owing to the excellent conductivity and electrochemical activity. In this work, the novel composite Co(OH)F@CoP core-shell nanoarrays, used as electrode material for supercapacitors, was synthesized on conductive carbon cloth (CC) through the hydrothermal method and phosphating process. The specific capacitance of Co(OH)F@CoP/CC is 654mC cm−2 at 1 mA·cm−2, and maintains long-life cycling stability of 71.34 % retention after 10,000 cycles at 10 mA·cm−2 in a three electrode system. Furthermore, a two-electrode system assembled by Co(OH)F@CoP and reduced graphene oxide (RGO) exhibits performance with energy density of 17.933 Wh kg−1 at power density of 800 W kg−1. These results proved that the Co(OH)F@CoP composite is an advanced electrode material for the supercapacitors.

Investigations on structural, morphological and electrochemical properties of Co(OH)2 nanosheets embedded carbon nanotubes for supercapacitor applications

The nanostructured cobalt hydroxide [Co(OH)2] embedded carbon nanotubes (CNT) have been synthesised by a simple chemical reflux method. The crystallinity of cobalt hydroxide has been confirmed by using powder X-ray diffraction data. The presence of CNT in the synthesised nanocomposite is also examined. Fourier transform infrared spectroscopy reveals the OH and CoO vibrations in the Co(OH)2/fCNT nanocomposite. SEM and TEM images expose the surface morphology of Co(OH)2 sheet that is embedded over carbon nanotube. The electrochemical performance of the Co(OH)2 embedded fCNT has been examined by the cyclic voltammetry in 6 M potassium hydroxide (KOH) electrolyte in room temperature. Co(OH)2 embedded fCNT nanocomposite exhibits higher specific capacitance up to 1006.8 F/g at 0.5 mV s−1 scan rate. The specific capacitance of Co(OH)2 embedded fCNT nanocomposite is calculated from the charge-discharge curve. The synthesised hybrid nanocomposite is used as a cathode, and the functionalized CNT is used as an anode. These are used to fabricate an asymmetrical supercapacitor device. The device is delivered to a high power density of 7000 W kg−1 and energy density of 17 W h kg−1 in the potential window from 0 V to 1.4 V. The results of hybrid Co(OH)2/fCNT||fCNT asymmetrical supercapacitor exhibit better cycle stability up to 5000 cycles. The usefulness of Co(OH)2/fCNT||fCNT asymmetrical supercapacitor is analysed for energy storage devices.

Effective enhancement of electrochemical energy storage of cobalt-based nanocrystals by hybridization with nitrogen-doped carbon nanocages

Cobalt-based oxygenic compounds Co(OH)2, CoO and Co3O4 are attractive for electrochemical energy storage owing to their high theoretical capacities and pseudocapacitive properties. Despite the great efforts to their compositional and morphological regulations, the performances to date are still quite limited owing to the low active surface area and sluggish charge transfer kinetics. Herein, different Co-based nanocrystals (Co-NCs) were conveniently anchored on the hierarchical nitrogen-doped carbon nanocages (hNCNCs) with high specific surface area and coexisting micro-meso-macropores to decrease the size and facilitate the charge transfer. Accordingly, a high specific capacity of 1170 F g−1 is achieved at 2 A g−1 for the Co(OH)2/hNCNCs hybrid, in which the capacitance of Co(OH)2 (2214 $${\rm{F\;g}}_{\rm{Co({OH})_2}}^{ - 1}$$ ) is approaching to its theoretical maximum (2595 F g−1), demonstrating the high utilization of active materials by the hybridization with N-doped nanocarbons. This study also reveals that these Co-NCs store/release electrical energy via the same reversible redox reaction despite their different pristine compositions. This insight on the energy storage of Co-based nanomaterials suggests that the commonly-employed transformation of the Co-NCs from Co(OH)2 to CoO and Co3O4 on carbon supports is unnecessary and even could be harmful to the energy storage performance. The result is instructive to develop high-energy-density electrodes from transition metal compounds.

Facial growth of Co(OH)2 nanoflakes on stainless steel for supercapacitors: effect of deposition potential

In this work, the nanoflakes of Co(OH)2 have been grown successfully on a stainless steel (SS) substrate at an ambient temperature. The novel architecture, binder free synthesis and considerable capacitance of Co(OH)2 nanoflakes render them as a potential candidate to be used as an electrode material for supercapacitor application. It is observed that the different cathodic potentials have a dramatic impact on the growth mechanism of Co(OH)2 nanoflakes. The prepared thin films were subjected for their structural and morphological study using X-ray diffraction, field emission scanning electron microscope, energy dispersive X-ray spectroscopy, etc. The supercapacitive properties of Co(OH)2 nanoflakes have been studied using cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy techniques. The Co(OH)2 nanoflakes evaluated a maximum specific capacitance of 275 F g−1 for 5 mV s−1 in 1 M KOH.

High area-specific capacitance of Co(OH)2/hierarchical nickel/nickel foam supercapacitors and its increase with cycling

Supercapacitors are important energy storage systems due to their high power densities compared to batteries, giving them unique applications.

A novel asymmetric supercapacitor with buds-like Co(OH)2 used as cathode materials and activated carbon as anode materials

In this work, Co(OH)2 buds direct growth on Ni foam (Co(OH)2 buds/Ni foam) is prepared via a hydrothermal method. Their structure and morphologies are characterized by using X-ray diffraction analysis, scanning electron microscopy and transmission electron microscopy. Result shows that the Co(OH)2 buds are assembled by several nanorods and uniformly covered on the surface of Ni foam. Due to its unique structure, the Co(OH)2 buds/Ni foam electrode shows high capacitive performance and long cycle life. The specific capacitance of Co(OH)2 buds/Ni foam is as high as 2041Fg−1 at a current density of 3mAcm−2 in 6M KOH electrolyte, and 811Fg−1 even at a high current density of 60mAcm−2. The capacitance of the Co(OH)2 buds/Ni foam electrode remained 72.4% after 1000 cycles at 18mAcm−2. An asymmetric supercapacitor was successfully assembled, in which Co(OH)2 buds/Ni foam and AC used as positive and negative electrode, respectively. The energy density of the AC//Co(OH)2 buds/Ni foam supercapacitor reaches to 20.3Whkg−1 at a power density of 90.6Wkg−1. Our result shows that the Co(OH)2 materials are promising candidate for electrochemical energy applications.

Supercapacitor performances of polyethylene glycol-intercalated Co(OH)2 nanoflakes by potentiodynamic deposition

Each Co(OH)2 and polyethylene glycol (PEG)-intercalated Co(OH)2 was potentiodynamically deposited from nitrate bath and their supercapacitor performances examined. The deposited hydroxides were characterized by X-ray diffraction, scanning electron microscopy and Fourier transformed infra-red spectroscopy. The supercapacitor behaviour of the hydroxides was examined by cyclic voltammetry and galvanostatic charge–discharge studies in 1 M KOH electrolyte. It was observed that the specific capacitance of Co(OH)2 could be tuned from 440 to 710 F g−1 at a current of 0.5 A g−1 by intercalating PEG into the interlayers of Co(OH)2. In addition, the 5 vol.% PEG-intercalated Co(OH)2 electrode exhibited highest specific capacitance and excellent cycle life with good retention of specific capacitance even up to 1000 charge–discharge cycles. The high specific capacitance and excellent cycle life of 5 vol.% PEG-intercalated Co(OH)2 were attributed to the better electrode/electrolyte interaction due to well-defined nano-flake morphology.

Tunable supercapacitor performance of potentiodynamically deposited urea-doped cobalt hydroxide

The influence of the basal length of Co(OH)2 on supercapacitor performance was examined in detail by adding simple urea molecules during deposition. It was observed that the specific capacitance of Co(OH)2 could be tuned from 700 to 1200 F g−1. This high specific capacitance was attributed to the better access of electrolyte.

Fabrication and Capacitance of Co3O4-Graphene Nanocomposites Electrode Prepared by Pulse Microwave-assisted Reduction Methods

Department of Chemistry, Inha University, Incheon 402-751, KoreaReceived August 9, 2012, Accepted September 19, 2012Key Words : Composite materials, Chemical synthesis, Electrochemical techniques, Electrochemical propertiesIn recent years, with an impending exhaustion of fossil fuelsand the rising global demand for an energy consumption, theeffort to maximize the utilization of present energy sourcesand a search for alternative energy storage devices has inten-sified dramatically.

Electrodeposition and characterization of ordered mesoporous cobalt hydroxide films on different substrates for supercapacitors

Novel ordered mesoporous cobalt hydroxide films have been successfully electrodeposited on different substrates, i.e., foamed nickel mesh and titanium plate, from cobalt nitrate dissolved in the aqueous domains of the hexagonal lyotropic liquid crystalline phase of Brij 56. Field emission scanning electron microscope (FESEM) and transmission electron microscopy (TEM) studies present that the as-deposited films have an interlaced nanosheet-like surface morphology and possess a regular nanostructure with hexagonal arrays of pores of nanometer dimension and extended periodicity. Various electrochemical test results show that the films on both substrates exhibit excellent electrochemical capacitive behavior due to the special ordered mesoporous nanostructure. Furthermore, it is obvious that the ordered mesoporous cobalt hydroxide film on foamed Ni mesh has much higher specific capacitance (maximum: 2646 F g −1) than that of the film on Ti plate (maximum: 1018 F g −1), which is mainly because that the foamed Ni mesh substrate with much larger surface area than Ti plate could enhance the utilization and the capacitance of Co(OH) 2 film greatly.