Electrochemical storage of hydrogen in activated carbon material has been investigated using different parameters of cathodic
polarization. It has been proven that application of short galvanostatic pulses could be efficient for hydrogen storage in
microporous carbon material. Charging current loads from 50 mA g−1 to 32 A g−1 have been used showing correlation between hydrogen capacity, time of charging and electrical efficiency. The anodic charge
equivalent to electrooxidation of 1.0 wt% of hydrogen can be already reached after 90 s of cathodic polarization. Temperature
effect has been also evaluated and a gradual increase of hydrogen capacity with a better pronounced oxidation plateau was
obtained at higher temperatures. Reversible electrosorption of hydrogen is a useful reaction in supercapacitor performance
and it might have a potential application for a negative electrode of supercapacitor as well as reversibly operating electrode
in the secondary cell.
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The paper discusses the efficiency of catalytic synthesis and structure of multi-wall carbon nanotubes obtained by acetylene decomposition over Mm (mischmetal)-based multi-component alloy of AB5 type. Different parameters of catalytic chemical vapor deposition process have an influence on the efficiency. Some of them were changed to obtain the highest amount of carbon material. The samples were purified by acid and were characterized by BET surface area measurements, scanning electron microscopy, and transmission electron microscopy analysis. However, both catalyst and parameters of process (such as the flow rate of acetylene) need further examination to make it cost effective. The capacitance properties of carbon nanotubes as electrode materials for electrochemical capacitors are discussed. It has been shown that carbon nanotubes show moderate values of capacitance. In the form of a network, the material provides good charge propagation and can be used as a support and additive for different composite electrode materials. 相似文献
Exceptional electrochemical behavior of carbon/iodide interface has been demonstrated and successfully used in supercapacitor application. This efficient charge storage is based on specific sorption of iodide ions as well as stable reversible redox reactions connected with various possible oxidation states of iodine from ?1 to +5. An intriguing effect of iodide ions has been observed for positive electrode operating in a narrow range of potential and giving extremely high capacitance values exceeding 1840 F/g. As opposed to typical pseudocapacitance effects, which are often characterized by some diffusion limitations and observed only at moderate regimes, our two-electrode system can be loaded until 50 A/g supplying still 125 F/g. Amazing capacitance of carbon/iodide interface has also been confirmed during long-term cycling (over 10 000 cycles). For the first time, such an innovative electrochemical system was successfully used for supercapacitor performance. The iodide ions play a useful dual role, i.e. electrolytic solution with a good ionic conductivity as well as a source of pseudo-capacitive effects. 相似文献
The activated carbon was modified by the wet method with a solution of ammonium persulfate at room temperature with different times. Kinetics studies showed that the modification took place mostly during the first 60 min of the process. The physicochemical properties of the obtained carbon were evaluated by thermogravimetric studies, Raman and FTIR spectroscopy, elementary and BET analyses. Furthermore, the fabricated material was applied in symmetric capacitors operated on the three aqueous electrolytes (1 M H2SO4, 6 M KOH and 1 M Na2SO4). Mild conditions of the modification process are optimal to obtain electroactive groups on the carbon surface, which make this material useful in a supercapacitor application. In our studies, we noticed that this type of functional groups mainly appears on the surface of the activated carbon, in the first oxidation stage. With prolonged oxidation, they may transform into undesirable groups. The results show that this kind of modification improves the capacity of all the tested supercapacitors. It was connected mainly with an increase of the carbon material’s wettability and in the case of capacitor operated in acid and base electrolytes due to a redox reaction of oxygen functional groups.
In the present study, a manganese oxide obtained by the acid treatment of LiMn2O4 spinel has been used as a positive electrode of supercapacitor. Removal of lithium from a spinel allowed to obtain MnO2 compound with the pores partly distributed in atomic scale, hence, an efficient use of its pseudocapacitive properties could
be reached. On the other hand, residual lithium remaining in the structure preserved layered framework of MnO2 with pathways for ions sorption. Physical properties, morphology, and specific surface area of electrode materials were studied
by scanning and transmission electron microscopy, and nitrogen sorption measurements. Voltammetry cycling, galvanostatic charge/discharge,
and impedance spectroscopy measurements performed in two- and three-electrode cells have been applied in order to measure
electrochemical parameters. Neutral Li2SO4 aqueous solution has been selected for electrolytic medium. Extension of operating voltage for supercapacitor has been realized
through asymmetric configuration with an activated carbon as a negative electrode. The asymmetric capacitor was operating
within a voltage range up to 2.5 V (limited to 2.0 V for cycling tests) and was able to deliver a specific capacitance of
60 Fg−1 per capacitor at 100 mA g−1 current density. High specific energy of 36 Wh kg−1 was reached but with a moderate power density. 相似文献
The direct borohydride fuel cell (DBFC) is a promising device that converts chemical energy into electricity by electrochemical reactions. This type of power source is technically more simple than traditional fuel cells, because it does not require any hydrogen container and noble metals. Hydrogen evolution during hydrolysis can be inhibited by modification of anode materials. Extensive studies are focused on various specific electrocatalysts and their impact on oxidation and hydrolysis of borohydride. The aim of the study is to determine the effect of anode material composition using borohydride as a fuel. In order to enhance the utilization of borohydride fuel, AB5-type alloy (LaMnNi3.55Al0.30Mn0.40Co0.75) was modified by adding Si or two kinds of carbon materials using the ball milling method. The most proper electrolyte was selected. The physical and electrochemical properties of anode materials were evaluated by scanning electron microscopy (SEM), cyclic voltammetry, chronopotentiometric measurements and electrochemical impedance spectroscopy. Studies showed that graphite was the best additive to anode material due to its density, compact structure and improvement of conductivity.
Journal of Solid State Electrochemistry - Combining the advantages of lithium-ion batteries and supercapacitors is an interesting solution to high-energy devices with the maintenance of high power... 相似文献
This paper presents a synthesis and characterizes highly amorphous lead dioxide and its use in hybrid electrochemical capacitor C/PbO2. Highly amorphous lead dioxide with a small amount of β-PbO2 was synthesized by galvanostatic deposition from acetate solution. The hybrid supercapacitor was constructed with PbO2 as the positive electrode whereas activated carbon as the negative electrode. The morphology of materials was examined by scanning electron microscopy and their structure was characterized by means of an X-ray diffraction technique. The electrochemical performance of hybrid electrochemical capacitor with synthesized PbO2 was studied by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. To indicate that the amorphous form of lead dioxide was predominant, results were compared to highly crystalline β-PbO2. The hybrid electrochemical capacitor with synthesized material exhibits a much greater specific capacitance, higher specific energy and power than the highly crystalline one. The specific capacitance values obtained for the supercapacitor rose more than twice in favour of amorphous PbO2. Also, long cycling did not influence any of the electrochemical properties of this hybrid electrochemical capacitor, which makes it an interesting energy storage device. 相似文献
Novel trigeminal tricationic ionic liquids (TTILs) have been successfully synthesized in high yields by means of Menschutkin quaternization via an S(N)1 mechanism. This reaction presents a new convenient method for transforming glycerol into multifunctional compounds. The physical properties of a series of TTILs were characterized by using a variety of techniques. The prepared salts were tested for antimicrobial activity. Electrochemical characterization of TTILs was also performed, which allowed the estimation of the conductivity of these new compounds, to establish their electrochemical stability window and capacitance properties over a wide range of temperatures. A good correlation of the physical properties of TTILs with capacitance values was observed. 相似文献