Search

new porous cobalt hydroxide film has been successfully electrodeposited on nickel foam from 0.1 M cobalt nitrate electrolyte at −1.0 V vs. SCE without adding any surfactant. The microstructure and surface morphology of prepared cobalt hydroxide films were physically characterized by X-ray diffraction analysis and scanning electron microscopy. The results indicate that an interlaced network structure was obtained. The effects of electrodeposition time, deposition potential, and different substrates on the specific capacitance and microstructure of prepared porous α-Co(OH) thin film were systematically studied. The results indicate that the film deposited on nickel foam at −1.0 V has excellent electrochemical properties. A maximum specific capacitance of 1473 F g could be achieved at a current density of 2 A g. [ABSTRACT FROM AUTHOR]

In this work, Co0.56Ni0.44 oxide nanoflakes with a maximum specific capacitance of 1227 F/g (136 mAh/g) are successfully synthesized by a facile chemical coprecipitation method. To enhance energy density, an asymmetric supercapacitor with high energy and power density has been constructed with Co0.56Ni0.44 oxide nanoflakes as the positive electrode and activated carbon as the negative electrode. The performance of the asymmetric supercapacitor was characterized by cyclic voltammetry and chronopotentiometry technology. By using the nanoflakes Co0.56Ni0.44 oxides electrode, the asymmetric supercapacitor exhibits high energy density and stable power characteristics; the maximum specific capacitance of 97 F/g and specific energy of 34.5 W h/kg are demonstrated for a cell voltage between 0 and 1.6 V. [ABSTRACT FROM AUTHOR]

In this work, stabilized Al-substituted α-Ni(OH)2 materials were successfully synthesized by a chemical coprecipitation method. The experimental results showed that the 7.5% Al-substituted α-Ni(OH)2 materials exhibited high specific capacitance (2.08 × 103 F/g) and excellent rate capability due to the high stability of Al-substituted α-Ni(OH)2 structures in alkaline media, suggesting its potential application in electrode material for supercapacitors. To enhance energy density, an asymmetric type pseudo/electric double-layer capacitor was considered where α-Ni(OH)2 materials and activated carbon act as the positive and negative electrodes, respectively. Values for the maximum specific capacitance of 127 F/g and specific energy of 42 W·h/kg were demonstrated for a cell voltage between 0.4 and 1.6 V. By using the α-Ni(OH)2 electrode, the asymmetric supercapacitor exhibited high energy density and stable power characteristics. The hybrid supercapacitor also exhibited a good electrochemical stability with 82% of the initial capacitance over consecutive 1,000 cycle numbers. [ABSTRACT FROM AUTHOR]

Polypyrrole (PPy) film-coated stainless steel electrodes were prepared from aqueous solution containing 0.5 M p-toluene sulphonic acid and 0.1 M pyrrole using pulse galvanostatic method (PGM) and galvanostatic method (GM). The morphology was characterized by scanning electron microscopy. The electrochemical properties of PPy films were investigated with cyclic voltammetry, charge–discharge tests, and ac impedance spectroscopy. The results showed that the PGM-PPy films exhibited higher specific capacitance, better high-rate discharge ability and lower resistance, and were more promising for applications in supercapacitor than GM-PPy films. The specific capacitance (SC) of PGM-PPy films was 403 F g−1 in 1 M H2SO4 electrolyte and 281 F g−1 in 1 M NaNO3 electrolyte. [ABSTRACT FROM AUTHOR]

Cobalt hydroxide nanoflakes with a maximum specific capacitance of 735 F/g are successfully synthesized by a facile chemical precipitation method. To enhance energy density, an asymmetric-type pseudo/electric double-layer capacitor is considered where Co(OH)2 nanoflakes and activated carbon act as the positive and negative electrodes, respectively. The electrochemical properties of the two electrodes and the asymmetric supercapacitor are investigated in 2 M KOH aqueous electrolyte. Values for the maximum specific capacitance of 72.4 F/g and specific energy of 92.7 Wh/kg are demonstrated for a cell voltage between 0 and 1.6 V. By using the nanoflake Co(OH)2 electrode, the asymmetric supercapacitor exhibits high energy density and stable power characteristics. The hybrid supercapacitor also exhibited a good electrochemical stability with 93.2% of the initial capacitance over consecutive 1000 cycle numbers. [ABSTRACT FROM AUTHOR]

A novel composite of Ni(OH)2/ultra-stable Y zeolite materials was synthesized by an improved chemical precipitation method, which used the ultra-stable Y zeolite as the template. The Ni(OH)2/ultra-stable Y zeolite composite and its microstructure were characterized by X-ray diffraction measurements and transmission electron microscopy. Electrochemical studies were carried out using cyclic voltammetry, chronopotentiometry technology and ac impedance spectroscopy, respectively. The result shows that the loose-packed whisker Ni(OH)2 phase has profound impacts on electrode performance at very high power output. A maximum discharge capacity of 185.6 mA-h/g (1670 F/g), or 371 mA-h/g (3340 F/g) after correcting for weight percent of nickel hydroxide phase at the current density of 625 mA/g could be achieved in a half-cell setup configuration for the Ni(OH)2/ultra-stable Y zeolite electrode, suggesting its potential application in electrode material for secondary batteries and electrochemical capacitors. Furthermore, the effect of NH4Cl concentration on the electrochemical properties characteristics has also been systemically explored. [ABSTRACT FROM AUTHOR]

Abstract  Loose-packed nickel hydroxides were successfully synthesized by a facile chemical precipitation method. Structure characterizations indicate that a nanoflake structure with low crystallinity for the nickel hydroxide samples was obtained. Electrochemical studies were carried out using cyclic voltammetry, chronopotentiometry technology, and alternating current impedance spectroscopy, respectively. A maximum specific capacitance of 2,055F/g could be achieved in 2M aqueous KOH with the potential range of 0 to 0.4V (vs. the saturated calomel electrode) in a half-cell setup configuration for the nanoflake Ni(OH)2 electrode, suggesting its potential application in the electrode material for electrochemical capacitors. Furthermore, the effect of annealing temperatures on the electrochemical capacitance characteristics has also been systemically explored. [ABSTRACT FROM AUTHOR]

Multi-walled carbon nanotubes (MWNTs)/polyaniline (PANI) composite materials were prepared by in-situ chemical oxidative polymerization of an aniline solution containing well-dispersed MWNTs. The supercapacitive behaviors of these composite materials were investigated with cyclic voltammetry (CV), charge–discharge tests, and ac impedance spectroscopy, respectively. The composites based on the charge-transfer complex between well-dispersed MWNTs and PANI matrixes show much higher specific capacitance, better thermal stability, lower resistance, and were more promising for applications in supercapacitors than a pure PANI electrode. The highest specific capacitance value of 224 Fg−1 was obtained for the MWNTs/PANI composite materials containing MWNTs of 0.8 wt%. The improvement mechanisms of the capacitance of the composite materials were also discussed in detail. [ABSTRACT FROM AUTHOR]

The electron emission characteristics of the Spindt-type Mo FEA device fabricated in this research are compared with numerical results. The authors propose an area model of the chip used for the analysis of the model based on the device structure. Further, by defining the factor ψ in a broad sense to enhance the numerical accuracy, adequate numerical results are obtained. Various characteristics are simulated by the Fowler–Nordheim equation based on the experimental data. The results computed in accordance with the model agree well with the experimental results based on SEM observation of the device. Hence, the tip radius of a device with fine sharpness can be estimated. © 2001 Scripta Technica, Electron Comm Jpn Pt 2, 84(3): 53–60, 2001 [ABSTRACT FROM AUTHOR]

The adsorption of H2 on two kinds of Mg3N2(110) crystal surface is studied by first principles. Adsorption sites, adsorption energy, and the electronic structure of the Mg3N2 (110)/H2 systems are calculated separately. It is found that H2 is mainly adsorbed as chemical adsorption, on these sites the H2 molecules are dissociated and the H atoms tend to the top of two N, respectively, forming two NH, or the H atoms tend to the same N forming one NH2. There are also some physical adsorption sites. One of the bridge sites of Mg3N2(110) surface is more favorable than the other sites. On this site, H atoms tend to the top of two N, forming two NH. This process belongs to strong chemical adsorption. The interaction between H2 molecule and Mg3N2(110) surface is mainly due to the overlap-hybridization among H 1s, N 2s, and N 2p states, covalent bonds are formed between the N and H atoms. [ABSTRACT FROM AUTHOR]

The adsorption of H2 molecule on LaFeO3(110) surface was studied by first-principle calculations. Based on the adsorption sites, adsorption energies, and electronic structures, it can be found that one H atom can be adsorbed on O atom and form -OH with the O atom, which is the most stable structure. One H atom can be adsorbed on one Fe atom, which makes Fe3+ turn to Fe2+. Two H atoms can form H2O molecule with O atom, which makes it possible to form oxygen vacancy on the surface. [ABSTRACT FROM AUTHOR]