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1.
Bo Gao 《Electrochimica acta》2010,55(11):3681-11258
Amorphous RuO2·xH2O was well coated on the benzenesulfonic functionalized multi-wall carbon nanotubes (f-MWCNTs) successfully via hydrothermal method. The decorated benzenesulfonic groups served as a bifunctional role both for solubilizing and dispersing MWCNTs into aqueous solution and for tethering Ru3+ precursor to facilitate the following uniform chemical deposition of RuO2·xH2O. The electrochemical performance of RuO2/f-MWCNTs and utilization of RuO2·xH2O were evidenced by cyclic voltammetry and galvanostatic charge/discharge tests. The specific capacitance of 1143 Fg−1 for RuO2·xH2O was obtained from RuO2/f-MWCNTs with 32 wt.% RuO2·xH2O, which was much higher than that of just 798 Fg−1 for the RuO2/p-MWCNTs. Even though the RuO2·xH2O loading increases to 45 wt.%, the utilization of RuO2·xH2O still possesses as high as 844.4 Fg−1, indicating a good energy capacity in the case of high loading. 相似文献
2.
Hydrous ruthenium dioxide (RuO2·xH2O) prepared in a modified sol-gel process was subjected to annealing in air and water at various temperatures for supercapacitor applications. The textural and pseudocapacitive characteristics of RuO2·xH2O annealed in air and water were systematically compared to show the benefits of annealing in water (denoted as hydrothermal annealing). An important concept that hydrothermal annealing effectively restricts condensation of hydroxyl groups within nanoparticles, inhibits crystal growth, and maintains high water content of RuO2·xH2O is demonstrated in this work. The unique textural characteristics of hydrothermally annealed RuO2·xH2O are attributable to the high-pressured, water-enriched surroundings which restrain coalescence of RuO2·xH2O nanocrystallites. The crystalline, hydrous nature of hydrothermally annealed RuO2·xH2O favors the utilization of active species in addition to a merit of minor dependence of specific capacitance on the scan rate of CV for pseudocapacitors. As a result, RuO2·xH2O with hydrothermal annealing at 225 °C for 24 h exhibits 16 wt.% water, an average particle size of about 7 nm, and specific capacitance of ca. 390 F g−1. 相似文献
3.
Co3O4 thin film is synthesized on ITO by a chemical bath deposition. The prepared Co3O4 thin film is characterized by X-ray diffraction, and scanning electron microscopy. Electrochemical capacitive behavior of synthesized Co3O4 thin film is investigated by cyclic voltammetry, constant current charge/discharge and electrochemical impedance spectroscopy. Scanning electron microscopy images show that Co3O4 thin film is composed of spherical-like coarse particles, together with some pores among particles. Electrochemical studies reveal that capacitive characteristic of Co3O4 thin film mainly results from pseudocapacitance. Co3O4 thin film exhibits a maximum specific capacitance of 227 F g−1 at the specific current of 0.2 A g−1. The specific capacitance reduces to 152 F g−1 when the specific current increases to 1.4 A g−1. The specific capacitance retention ratio is 67% at the specific current range from 0.2 to 1.4 A g−1. 相似文献
4.
X.M. Liu 《Electrochimica acta》2004,49(2):229-232
NiO/RuO2 composite materials were prepared for use in electrochemical capacitors (ECs) by co-precipitation method followed by heat treatment. X-ray diffraction (XRD) spectra indicated that no new structural materials were formed and ruthenium oxide particles were coated by NiO particles. RuO2 partly introduced into NiO-based electrode had improved its electrochemical performance and capacitive properties by using electrochemical measurements. A maximum specific capacitance of 210 F/g was obtained for NiO-based composite electrode with 10 wt.% RuO2 in the voltage range from −0.4 to 0.5 V in 1 mol/l KOH solution. By comparison of effect of modified modes on the specific capacitance, chemically modified composite electrodes had more stable cycling properties than those of physically modified electrodes. After 200 cycles, specific capacitance of NiO-based chemical composite electrode with 5 wt.% RuO2 kept 95% above, while that of physical electrode was only 79% of initial specific capacitance. 相似文献
5.
The electrochemical energy storage and delivery on the electrodes composed of hydrous ruthenium oxide (RuOx·nH2O) or activated carbon-hydrous ruthenium oxide (AC-RuOx) composites are found to strongly depend on the substrate employed. The contact resistance at the active material-graphite interface is much lower than that at the active material-stainless steel (SS) mesh interface. Thin films of gold plus RuOx·nH2O deposited on SS meshes (RuOx/Au/SS) are found to greatly improve the poor contact between SS meshes and electrode materials. The maximum specific capacitance (CS,RuOx) of RuOx·nH2O, 1580 F g−1 (measured at 1 mV s−1), very close to the theoretic value, was obtained from an AC-RuOx/RuOx/Au/SS electrode with 10 wt.% sol-gel-derived RuOx·nH2O annealed in air at 200 °C for 2 h. The highly electrochemical reversibility, high-power characteristics, good stability, and improved frequency response of this AC-RuOx/RuOx/Au/SS electrode demonstrate its promising application potential in supercapacitors. The ultrahigh specific capacitance of RuOx·nH2O probably results from the uniform size distribution of RuOx·nH2O nanoparticles, ranged from 1.5 to 3 nm which is clearly observed from the high-resolution transmission electron microscopy (HRTEM). 相似文献
6.
Suhua Ma Xiaodong Shen Xueping Gong Baiqian Zhong 《Cement and Concrete Research》2006,36(9):1784-1787
The influence of CuO on the formation and coexistence of 3CaO·SiO2 and 3CaO·3Al2O3·CaSO4 minerals in Portland cement containing 3CaO·3Al2O3·CaSO4 mineral is reported in this paper. The results show that a suitable amount of CuO can lower the clinkering temperature and improve the burn-ability of clinkers. It can also promote the formation of 3CaO·SiO2 and 3CaO·3Al2O3·CaSO4 minerals and facilitate the coexistence of the two minerals in the clinkers. But adding 1% CuO to the raw material can cause the decomposition of 3CaO·3Al2O3·CaSO4. 相似文献
7.
A facile and rapid microwave-assisted combustion method was developed to synthesize the nanocrystalline Co3O4. The study suggested that application of microwave heating to produce the homogeneous porous Co3O4 was achieved in a few minutes. The structure and morphology of the as-prepared nanocrystalline Co3O4 were investigated by means of X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), Raman spectra, UV-vis absorbance spectra and scanning electron microscopy (SEM). The XRD, FTIR and Raman spectra confirmed the formation of spinel structural Co3O4, and the SEM results indicated the porous surface characteristic of the products. Magnetic measurement was carried out using a vibrating sample magnetometer (VSM). The field dependence of the magnetization at room temperature showed a tiny hysteresis loop with a coercivity of 56.7 Oe. 相似文献
8.
2ZnO·3B2O3·3H2O is an industrially important zinc borate. Herein, 2ZnO·3B2O3·3H2O has been prepared via a rheological phase reaction method using zinc oxide and boric acid as starting materials. This route is facile and acceptable for green chemical synthesis, producing no pollution and giving a yield of near 100% of theoretical value. And in this method, the complete conversion of the starting materials can be achieved in the presence of only 0.04 mL water (one drop of water). The products have been characterized by X-ray powder diffraction (XRD), thermogravimetry (TG) and differential thermal analysis (DTA), scanning electron microscopy (SEM) and particle size distribution. The effects of experimental conditions on the products were investigated. The main factors that affect the formation of zinc borate are water volume, sealing state, reaction time and temperature. 相似文献
9.
Cathode active materials with a composition of LiNi0.9Co0.1O2 were synthesized by a solid-state reaction method at 850 °C using Li2CO3, NiO or NiCO3, and CoCO3 or Co3O4, as the sources of Li, Ni, and Co, respectively. Electrochemical properties, structure, and microstructure of the synthesized LiNi0.9Co0.1O2 samples were analyzed. The curves of voltage vs. x in LixNi0.9Co0.1O2 for the first charge–discharge and the intercalated and deintercalated Li quantity Δx were studied. The destruction of unstable 3b sites and phase transitions were discussed from the first and second charge–discharge curves of voltage vs. x in LixNi0.9Co0.1O2. The LiNi0.9Co0.1O2 sample synthesized from Li2CO3, NiO, and Co3O4 had the largest first discharge capacity (151 mA h/g), with a discharge capacity deterioration rate of −0.8 mA h/g/cycle (that is, a discharge capacity increasing 0.8 mA h/g per cycle). 相似文献
10.
In this study, single crystal V3O7·H2O nanobelts were successfully synthesized using a simple hydrothermal route, in which templates or catalysts were absent. The synthesized V3O7·H2O nanobelts are highly crystalline and have lengths up to several tens of micrometers. The width and thickness of the nanobelts are found to be about 30-50 and 30 nm, respectively. A lithium battery using V3O7·H2O nanobelts as the positive electrode exhibits a high initial discharge capacity of 409 mAh g−1, corresponding to the formation of LixV3O7·H2O (x = 4.32). Such a high degree of electrochemical performance is attributed to the intrinsic properties of the single-crystalline V3O7·H2O nanobelts. 相似文献
11.
The growth kinetics of nanograins in Co3O4 nanofibers has been investigated. Individual fibers were made up of nanograins. The nanograins were observed to coalesce and grow at the expense of the smaller ones, similar to the phenomenon observed in the sintering process of bulk ceramics. The activation energy and the growth kinetics of nanograins were estimated, showing the dominant growth mechanism of nanograins to be likely related to a lattice diffusion process. 相似文献
12.
The influence of MgO on the formation of Ca3SiO5 and 3CaO·3Al2O3·CaSO4 minerals in alite-sulphoaluminate cement is reported in this paper. The results show that adding a suitable amount of MgO can lower the clinkering temperature, promote the formation of Ca3SiO5 and 3CaO·3Al2O3·CaSO4 minerals, and help in the coexistence of the two minerals in the clinker. MgO may obviously decrease the formation of Ca3Al2O6, and increase the SiO2 content incorporated into the interstitial phase. 相似文献
13.
Fernando Pico Teresa A. Centeno Rosa M. Rojas Jose M. Rojo 《Electrochimica acta》2006,51(22):4693-4700
RuO2·xH2O/NiO composites having RuO2 contents in the range 0-100 wt.% have been prepared by a co-precipitation method. Structural, microstructural and textural transformations after heating the as-prepared composites at 200 and 600 °C have been followed by X-ray diffraction, scanning electron microscopy (SEM) and nitrogen adsorption/desorption isotherms. At 200 °C the composites are made of micrometric particles in which nanometric crystallites of the two oxides are aggregated. The composites show microporosity (0.02-0.10 cm3/g), mesoporosity (0.07-0.12 cm3/g) and relatively high specific surface area (62-309 m2/g). At 600 °C the composites are fully dehydrated and RuO2 has crystallized and segregated. Microporosity and mesoporosity as well as specific surface area are strongly decreased. Specific capacitance and specific surface area of the composites heated at 200 and 600 °C have been measured and discussed on the basis of the RuO2 content. For comparison the specific capacitance and specific surface area of mixtures of NiO and RuO2·xH2O (or RuO2) have been taken as references. The higher specific capacitance of the 200 °C-heated composites compared to the 600 °C-heated ones is due to the higher specific surface area of the former and the higher pseudocapacitance of RuO2·xH2O compared to RuO2. The discussion reported in this work can be applied to other composites such as RuO2·xH2O/carbon and RuO2·xH2O/other oxides. 相似文献
14.
Ultrafine powders of LiCoO2, nonstoichiometric LiNiO2 and LiNi0.9Co0.1O2 were prepared under mild hydrothermal conditions. The influence of the molar ratio of Li/Co, Li/Ni and Li/(Ni + Co) was studied. The final products were investigated by XRD, TEM and EDS. To synthesize a stoichiometric LiNiO2 under mild hydrothermal conditions was found to be a big challenge. Transmission electron microscopies (TEM) revealed the formation of well-crystallized LiCoO2 and LiNi0.9Co0.1O2 with average size of 100 nm and 10 nm, respectively. 相似文献
15.
Yuanguang Zhang Youcun Chen Tao Wang Juhong Zhou Yinguo Zhao 《Microporous and mesoporous materials》2008,114(1-3):257-261
Nanoporous Co3O4 hierarchical nanoflowers have been prepared through sequential process of a hydrothermal reaction and heat treatment. These nanoflowers consisting of a great deal of Co3O4 nanofibers have bimodal pore structures and Brunauer–Emmett–Teller surface area of 34.61 m2/g. The temperature dependence curves of magnetization in zero-field-cooled and field-cooled exhibit main antiferromagnet and weak ferromagnet of Co3O4 nanoflowers at blocking temperature of 34 K, respectively. In addition, analysis of their optic properties obviously indicates red shift of absorption peaks, exhibiting quantum-confined effect and traits of semiconductor. 相似文献
16.
Wen Juan Xue Yu Fei Wang Peng Li Zhao-Tie Liu Zheng Ping Hao Chun Yan Ma 《Catalysis communications》2011,12(13):1265-1268
Au/Co3O4 catalysts with different morphologies (nanorods, nanopolyhedra and nanocubes) were successfully synthesized and evaluated for ethylene complete oxidation. We found that support morphology has a significant effect on catalytic activity, which is related to the exposed planes of different morphological Co3O4. HRTEM revealed the Co3O4-nanorods predominantly exposes {110} planes, while the dominant exposed planes of Co3O4-nanopolyhedra and -nanocubes are {011} and {001} planes, respectively. Compared with {011} and {001} planes, {110} planes exhibit the maximum amount of oxygen vacancies, which play a major role in ethylene oxidation. Therefore, Au/Co3O4-nanorods exhibits extraordinary catalytic activity, yielding 93.7% ethylene conversion at 0 °C. 相似文献
17.
Amorphous hydrated iron (III) phosphate has been synthesized by a coordinate precipitation method from equimolecular Fe(NO3)3 and (NH4)2HPO4 solutions at an elevated temperature. Hydrated iron (III) phosphate samples and the corresponding LiFePO4/C products were characterized by XRD and SEM. The electrochemical behavior was studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The LiFePO4/C fabricated from as-synthesized FePO4 delivered discharge capacities of 162.5, 147.3, 133.0, 114.7, 97.2, 91.3 and 88.5 mAh g−1 at rates of 0.1C, 0.2C, 0.5C, 1C, 2C, 3C and 4C with satisfactory capacity retention, respectively. 相似文献
18.
Lianqi Zhang Xiaoqing Wang Masaki Yoshio Takayoshi Sasaki 《Electrochimica acta》2004,49(20):3305-3311
An attempt to understand the unusual electrochemical behaviors in (1−x)LiNiO2·xLi2TiO3 (0.05≤x≤0.5), an excess initial charge capacity exceeding the oxidation of transitional metal to +4 accompanying the appearance of an irreversible initial charge plateau when x reached 0.075, was performed. The decreased charge-discharge polarization after charging to 4.6 and 4.8 V and increased columbic reversibility after charging to 4.6 V typically for x=0.1 and 0.2, in contrast to charging to 4.4 V, suggested that the excess initial charge capacity possibly did not come mainly from electrolyte decomposition; while ex situ XRD results in the sample with x=0.2 confirmed that Li+ were really extracted at the stage of the charge plateau, ruling out the possibility that electrolyte decomposition mainly accounted for the unusual electrochemical behaviors. It was inferred that the species responsible for charge compensation for the excess charge capacity must be oxygen ions in these materials, considering that Ni4+ and Ti4+ are generally impossible to be oxidized to a higher valence. Various electrochemical cycling experiments demonstrated that the sample for x=0.05 with high resistant ability to high voltage and temperature is very promising cathode material in view of observed capacity and cycleability from a viewpoint of application. 相似文献
19.
Cobalt oxide-doped copper oxide composite nanofibers (CCNFs) were successfully achieved via electrospinning followed by thermal treatment processes and then exploited as active electrode material for direct enzyme-free fructose detection. The morphology and the structure of as-prepared samples were investigated by X-ray diffraction spectrum (XRD) and scanning electron microscopy (SEM). The electrocatalytic activity of CCNFs films towards fructose oxidation and sensing performances were evaluated by conventional electrochemical techniques. Cyclic voltammetry (CV) and chronoamperometry (I−t) revealed the distinctly enhanced sensing properties towards fructose compared to pure copper oxide nanofibers (CNFs), i.e., showing significantly lowered overpotential of 0.30 V, ultrafast (1 s) and ultrasensitive (18.988 μA mM−1) current response in a wide linear range of 1.0 × 10−5 M to 6.0 × 10−3 M with satisfied reproducibility and stability, which could be ascribed to the synergic catalytic effect of the binary CuO/Co3O4 composite nanofibers and the highly porous three-dimensional network films structure of the CCNFs. In addition, a good selectivity for fructose detection was achieved. Results in this work demonstrated that CCNFs is one of the promising catalytic electrode materials for enzymeless fructose sensor fabrication. 相似文献
20.
Cobalt oxide (Co3O4) nanotubes have been successfully synthesized by chemically depositing cobalt hydroxide in anodic aluminum oxide (AAO) templates and thermally annealing at 500 °C. The synthesized nanotubes have been characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). The electrochemical capacitance behavior of the Co3O4 nanotubes electrode was investigated by cyclic voltammetry, galvanostatic charge-discharge studies and electrochemical impedance spectroscopy in 6 mol L−1 KOH solution. The electrochemical data demonstrate that the Co3O4 nanotubes display good capacitive behavior with a specific capacitance of 574 F g−1 at a current density of 0.1 A g−1 and a good specific capacitance retention of ca. 95% after 1000 continuous charge-discharge cycles, indicating that the Co3O4 nanotubes can be promising electroactive materials for supercapacitor. 相似文献