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1.
Performance of templated mesoporous carbons in supercapacitors   总被引:1,自引:0,他引:1  
By analogy with other types of carbons, templated mesoporous carbons (TMCs) can be used as supercapacitors. Their contribution arises essentially from the double layer capacity formed on their surface, which corresponds to 0.14 F m−2 in aqueous electrolytes such as H2SO4 and KOH and 0.06 F m−2 for the aprotic medium (C2H5)4NBF4 in CH3CN. In the case of a series of 27 TMCs, it appears that the effective surface area determined by independent techniques can be as high as 1500-1600 m2 g−1, and therefore exceeds the value obtained for many activated carbons (typically 900-1300 m2 g−1). On the other hand, the relatively low amount of surface oxygen in the present TMCs, as opposed to activated carbons, reduces the contribution of pseudo-capacitance effects and limits the gravimetric capacitance to 200-220 F g−1 for aqueous electrolytes. In the case of non-aqueous electrolyte, it rarely exceeds 100 F g−1.It is also shown that the average mesopore diameter of these TMCs does not improve significantly the ionic mobility compared with typical activated carbons of pore-widths above 1.0-1.3 nm.This study suggests that activated carbons remain the more promising candidates for supercapacitors with high performances.  相似文献   

2.
This study shows that carbide-derived carbons (CDCs) with average pore size distributions around 0.9-1 nm and effective surface areas of 1300-1400 m2 g−1 provide electrochemical double-layer capacitors with high performances in both aqueous (2M H2SO4) and aprotic (1M (C2H5)4NBF4 in acetonitrile) electrolytes.In the acidic electrolytic solution, the gravimetric capacitance at low current density (1 mA cm−2) can exceed 200 F g−1, whereas the volumetric capacitance reaches 90 F cm−3. In the aprotic electrolyte they reach 150 F g−1 and 60 F cm−3.A detailed comparison of the capacitive behaviour of CDCs at high current density (up to 100 mA cm−2) with other microporous and mesoporous carbons indicates better rate capabilities for the present materials in both electrolytes. This is due to the high surface area, the accessible porosity and the relatively low oxygen content.It also appears that the surface-related capacitances of the present CDCs in the aprotic electrolyte are in line with other carbons and show no anomalous behaviour.  相似文献   

3.
A series of coal-based activated carbons representing a wide range of mesopore content, from 16.7 to 86.9%, were investigated as an electrode in electric double layer capacitors (EDLCs) in 1 mol l−1 H2SO4 and 6 mol l−1 KOH electrolytic solutions. The activated carbons (ACs) used in this study were produced from chemically modified lignite, subbituminous and bituminous coals by carbonization and subsequent activation with steam. The BET surface area of ACs studied ranged from 340 to 1270 m2 g−1. The performance of ACs as EDLC electrodes was characterized using voltammetry, galvanostatic charge/discharge and impedance spectroscopy measurements. For the carbons with surface area up to 1000 m2 g−1, the higher BET surface area the higher specific capacitance (F g−1) for both electrolytes. The surface capacitance (μF cm−2) increases also with the mesopore content. The optimum range of mesopore content in terms of the use of ACs studied for EDLCs was found to be between 20 and 50%. A maximum capacitance exceeding 160 F g−1 and a relatively high surface capacitance about 16 μF cm−2 measured in H2SO4 solution were achieved for the AC prepared from a sulfonated subbituminous coal. This study shows that the ACs produced from coals exhibit a better performance as an electrode material of EDLC in H2SO4 than in KOH electrolytic solutions. For KOH, the capacitance per unit mesopore surface is slightly lower than that referred to unit micropore surface (9.1 versus 10.1 μF cm−2). However, in the case of H2SO4 the former capacitance is double and even higher compared with the latter (23.1 versus 9.8 μF cm−2). On the other hand, the capacitance per micropore surface area is the same in both electrolytes used, about 10.0 μF cm−2.  相似文献   

4.
V. Ruiz 《Electrochimica acta》2010,55(25):7495-7500
Polyfurfuryl alcohol (PFA) derived activated carbons were prepared by the acid catalysed polymerization of furfuryl alcohol, followed by potassium hydroxide activation. Activated carbons with apparent BET surface areas ranging from 1070 to 2600 m2 g−1, and corresponding average micropore sizes between 0.6 and 1.6 nm were obtained. The porosity of these carbons can be carefully controlled during activation and their performance as electrode materials in electric double layer capacitors (EDLCs) in a non-aqueous electrolyte (1 M Et4NBF4/ACN) is investigated.Carbon materials with a low average pore size (<∼0.6 nm) exhibited electrolyte accessibility issues and an associated decrease in capacitance at high charging rates. PFA carbons with larger average pore sizes exhibited greatly improved performance, with specific electrode capacitances of 150 F g−1 at an operating voltage window of 0-2.5 V; which corresponds to 32 Wh kg−1 and 38 kW kg−1 on an active material basis. These carbons also displayed an outstanding performance at high current densities delivering up to 100 F g−1 at current densities as high as 250 A g−1. The exceptionally high capacitance and power of this electrode material is attributed to its good electronic conductivity and a highly effective combination of micro- and fine mesoporosity.  相似文献   

5.
Effect of mesoporosity on specific capacitance of carbons   总被引:2,自引:0,他引:2  
The study compares the structural and electrochemical properties of 12 porous carbons based on phenolic resins, using both aqueous (H2SO4) and aprotic ((C2H5)4NBF4 in acetonitrile) electrolytes. It appears that they fit into the general pattern observed for other carbons. The present carbons have micropore volumes varying between 0.29 and 0.66 cm3 g−1 and average pore widths Lo between 0.62 and 1.23 nm. Five samples are exclusively microporous, whereas seven also display a relatively important mesoporosity. This allows a direct comparison between pairs of carbons with similar micropore systems, with and without mesopores, in order to assess the role of mesoporosity in the electrochemical properties. It appears that mesopores have only a limited influence on the decrease in capacitance at high current density as opposed to earlier assumptions.  相似文献   

6.
The activated carbon beads (ACB) are prepared by a new preparation method, which is proposed by mixing the coal tar pitch and fumed silica powder at a certain weight ratio and activation by KOH at different weight ratios and different temperatures. The BET surface area, pore volume and average pore size are obtained based on the nitrogen adsorption isotherms at 77 K by using ASAP 2010 apparatus. The results show that our samples have much high specific surface area (SSA) of 3537 m2 g−1and high pore volume value of 3.05 cm3 g−1. The percentage of mesopore volume increases with the weight ratio of KOH/ACB ranging from 4% to 72%. The electrochemical double layer capacitors (EDLCs) are assembled with resultant carbon electrode and electrolyte of 1 mol L−1 Et4NBF4/PC. The specific capacitance of the ACB sample could be as high as 191.7 F g−1 by constant current charge/discharge technique, indicating that the ACB presents good characteristics prepared by the method proposed in this work. The investigation of influence of carbon porosity structure on capacitance indicates that the SSA plays an important role on the capacitance and all the pore sizes of less than 1 nm, from 1 to 2 nm and larger than 2 nm contribute to the capacitance. Mesopore structure is beneficial for the performance at high current density.  相似文献   

7.
Juan Hu  Hongliang Guo 《Carbon》2010,48(12):3599-152
Several kinds of porous carbons were easily prepared by using metal-organic framework as both template and carbon precursor. Nanocasting is chosen to adjust the textures and structures with phenolic resin or carbon tetrachloride and ethylenediamine as the additional carbon sources. The carbon materials were further activated by potassium hydroxide (KOH). The electrochemical capacitance behaviors of these carbon materials were investigated in both aqueous and organic electrolytes. Energy densities of 9.4 W h kg−1 in 6 M KOH and 31.2 W h kg−1 in 1.5 M tetraethylammonium tetrafluoroborate acetonitrile solution can be obtained for one of the prepared porous carbon materials (MAC-A) with the surface area of 2222 m2 g−1 and the total pore volume of 1.14 cm3 g−1. Due to its high packing density of 0.93 g cm−3, the related volumetric specific energy densities of 8.8 and 29.0 W h L−1 can be got.  相似文献   

8.
Alar Jänes  Heisi Kurig  Enn Lust 《Carbon》2007,45(6):1226-1233
Commercial nanoporous carbon RP-20 was activated with water vapor in the temperature range from 950 °C to 1150 °C. The XRD analysis was carried out on nanoporous carbon powder samples to investigate the structural changes (graphitisation) in modified carbon that occurred at activation temperatures T ? 1150 °C. The first-order Raman spectra showed the absorption peak at 1582 cm−1 and the disorder (D) peak at 1350 cm−1. The low-temperature N2 adsorption experiments were performed at −196 °C and a specific surface area up to 2240 m2g−1 for carbon activated at T = 1050 °C was measured. The cell capacitance for two electrode activated nanoporous carbon system advanced up to 60 F g−1 giving the specific capacitance ∼240 F g−1 to one electrode nanoporous carbon ∣1.2 M (C2H5)3CH3NBF4 + acetonitrile solution interface. A very wide region of ideal polarisability for two electrode system (∼3.2 V) was achieved. The low frequency limiting specific capacitance very weakly increases with the rise of specific area explained by the mass transfer limitations in the nanoporous carbon electrodes. The electrochemical characteristics obtained show that some of these materials under discussion can be used for compilation of high energy density and power density non-aqueous electrolyte supercapacitors with higher power densities than aqueous supercapacitors.  相似文献   

9.
Activated carbon fiber cloth (ACFC) electrodes with high double layer capacitance and good rate capability were prepared from polyacrylonitrile (PAN) fabrics by optimizing the carbonization temperature prior to CO2 activation. The carbonization temperature has a marked effect on both the pore structure and the electrochemical performances of the ACFCs. Moderate carbonization at 600 °C results in higher specific surface area and larger pore size, and hence higher capacitance and better rate capability. The specific capacitance of the ACFCs in 6 mol L−1 KOH aqueous solution can be as high as 208 F g−1. It remains 129 F g−1 as the current density increases to 10 000 mA g−1.  相似文献   

10.
Nanowire-structured MnO2 active materials were prepared by a chemical precipitation method and their supercapacitive properties for use in the electrodes of supercapacitors were investigated by means of cyclic voltammetry in an aqueous gel electrolytes consisting of 1 M Na2SO4 and fumed silica (SiO2). The MnO2 electrode showed a maximum specific capacitance of 151 F g−1 after 1000 cycles at 100 mV s−1 when using the gel electrolyte containing 3 wt.% of SiO2, which is higher than 121 F g−1 obtained when using the 1 M Na2SO4 liquid electrolyte alone.  相似文献   

11.
Porous carbons with high-volumetric capacitance in aqueous electric double layer capacitors (EDLCs) were simply prepared by poly(vinylidene chloride) (PVDC) carbonization at high temperature without activation or any other additional processes. The PVDC-derived carbon is microporous with Brunauer-Emmett-Teller (BET) surface area about 1200 m2 g−1. As it possesses not only high-gravimetric capacitance (262 F g−1) but also high-electrode density (0.815 g cm−3), the PVDC-derived carbon present an outstanding high-volumetric capacitance of 214 F cm−3, twice over of the commercial carbon Maxsorb-3 with a high-surface area of 3200 m2 g−1. The PVDC-derived carbon also exhibit good rate performance, indicating that it is a promising electrode material for EDLCs.  相似文献   

12.
Bin Xu  Lu Peng  Gaoping Cao 《Carbon》2010,48(8):2377-13830
Mesoporous carbon has been synthesized using nano-CaCO3 as a template and sucrose as carbon precursor. It is shown that the CaCO3/sucrose weight ratio has a marked effect on the porosity of the carbon. At a weight ratio of CaCO3/sucrose of 1:1, the surface area of the carbon reaches 892 m2 g−1 and the pore size is around 45 nm. The carbon shows a capacitance of 155 F/g with excellent rate capability in 6 mol L−1 KOH aqueous electrolytes.  相似文献   

13.
In order to optimize the performance of supercapacitors, the capacitance of the carbon materials used as electrodes was strictly related to their pores size and also to their redox properties. Well-sized carbons have been elaborated through a template technique using mesoporous silica. For a series of template carbons, a perfect linear dependence has been found for the capacitance values versus the micropore volume determined by CO2 adsorption. The redox properties of carbons were enhanced by substituting nitrogen for carbon up to ca. 7 wt.%. For carbons with similar nanotextural characteristics, the electrochemical measurements showed a proportional increase of the specific capacitance with the nitrogen content in acidic electrolyte. For an activated carbon from polyacrylonitrile with a specific surface area of only 800 m2 g−1, but with a nitrogen content of 7 wt.%, the capacitance reaches 160 F g−1, with very little fading during cycling.  相似文献   

14.
A morphological characterization of activated AR-resin was carried out. The time and temperature effect of the EDLC (electric double layer capacitor) properties of AR-resin were investigated. In order to clarify the relation between the electric double layer capacitance and the ion mobility in the organic solvent, a computer simulation was used to calculate the possible solvation size of Et4NBF4 in propylene carbonate. The sample (HTT 700) activated at a heat treatment temperature (HTT) of 700 °C for 2 h has a specific capacitance as high as 35.27 F g−1 (equivalent to 141.08 F g−1 for a single electrode), when it is charged to 2.5 V and discharged at 1 mA cm−2. The capacitance increase by using a longer activation time at each HTT was as follows: 2.3 times at HTT 600, 1.6 times at HTT 700, 1.3 times at HTT 800 and 1.2 times at HTT 900. This variation could be forecast from image analysis using a TEM photograph. Furthermore, a possible ion size of electrolyte (Et4NBF4) in a solvent was calculated and it is related to the mobility of charge carriers in a micropore.  相似文献   

15.
Nitrogen-containing microporous carbons have been synthesized by the carbonization of anionic surfactant-melamine/formaldehyde (MF) composites, which were themselves formed by an electrostatic organic-organic interaction. The carbons prepared from sodium dioctyl sulfosuccinate-MF and sodium dodecyl sulfate-MF mixtures have high surface area of 464 and 539 m2 g−1, respectively. The N/C molar ratios of the carbons are 0.11. The resultant carbons showed capacitances higher than 200 F g−1 in an acidic solution of 1 M H2SO4 at a scan rate of 1 mV s−1.  相似文献   

16.
Graphene nanosheet (GNS)/Co3O4 composite has been rapidly synthesized by microwave-assisted method. Field emission scanning electron microscopy and transmission electron microscopy observation reveals the homogeneous distribution of Co3O4 nanoparticles (3-5 nm in size) on graphene sheets. Electrochemical properties are characterized by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. A maximum specific capacitance of 243.2 F g−1 has been obtained at a scan rate of 10 mV s−1 in 6 M KOH aqueous solution for GNS/Co3O4 composite. Furthermore, the composite exhibits excellent long cycle life along with ∼95.6% specific capacitance retained after 2000 cycle tests.  相似文献   

17.
Two kinds of functionalized graphene sheets were produced by thermal exfoliation of graphite oxide. The first kind of functionalized graphene sheets was obtained by thermal exfoliation of graphite oxide at low temperature in air. The second kind was prepared by carbonization of the first kind of functionalized graphene sheets at higher temperature in N2. Scanning electron microscopy images show that both two kinds of samples possess nanoporous structures. The results of N2 adsorption-desorption analysis indicate that both of two kinds of samples have high BET surface areas. Moreover, the second kind of functionalized graphene sheets has a relatively higher BET surface area. The results of electrochemical tests is as follows: the specific capacitance values of the first kind of functionalized graphene sheets in aqueous KOH electrolyte are about 230 F g−1; the specific capacitance values of the second kind of functionalized graphene sheets with higher BET surface areas are only about 100 F g−1; however, compared with the first kind of functionalized graphene sheets, the second kind has a higher capacitance retention at large current density because of its good conductive behaviors; furthermore, in non-aqueous EC/DEC electrolyte, the specific capacitance values of the first kind sample and the second kind sample are about 73 F g−1 and 36 F g−1, respectively.  相似文献   

18.
A hybrid supercapacitor based on manganese oxide, activated carbon and polymer electrolyte was developed and electrochemically investigated. The capacitive performance obtained from the polymer electrolyte based supercapacitor was similar to that of an aqueous electrolyte based supercapacitor, tested for comparison in the same operative conditions. A durability test carried out for 2500 cycles showed stable and slowly increasing performance. The specific capacitance of hybrid supercapacitor was 48 F g−1 (192 F g−1 as a mean one electrode capacitance), in which that of the positive electrode was 384 F g−1 of MnO2 and that of negative electrode 117 F g−1 of carbon. The impedance analysis evidenced that although the polymer electrolyte based hybrid supercapacitor showed higher resistance compared to that of the liquid electrolyte based supercapacitor, this drawback was counterbalanced by better ion transport features, which were evident at lower frequencies, where similar values of capacitances were obtained from the different supercapacitors.  相似文献   

19.
In this work we have explored the electrochemical properties of two lithiated iron oxide powders for supercapacitor purposes. These samples mainly consisted of α-LiFeO2 in nanosized or micrometric form. Electrolyte was an aqueous 0.5 M Li2SO4 solution and voltage range studied was between 0 and −0.7 V vs. a Ag/AgCl reference electrode. As expected, electrochemical performance was dependent on the particle size. When electrolyte was deaerated a stable capacitance of ≈50 F g−1 is provided by the nanosized sample for several hundred cycles. Other sulfate based salts (Na2SO4, K2SO4, Cs2SO4) were investigated as electrolytes but only Li2SO4 leads to a stable capacitance upon cycling, probably due to lithium intercalation. An hybrid cell consisting of this sample and MnO2 as negative and positive electrodes, respectively, delivered 0.3 F cm−2 (10 F g−1). Although these values are lower than reported for other aqueous hybrid cell, α-LiFeO2/MnO2 asymmetric capacitor is interesting from both, an economic and an environmental point of view.  相似文献   

20.
By modification of surfaces of multi-walled carbon nanotubes with ultra-thin monolayer-type films of phosphododecamolybdic acid, H3PMo12O40, an electrode material with improved capacitance properties is produced. It is apparent from three distinct test experiments (based on cyclic voltammetry, galavanostatic charging-discharging and AC impedance) that capacitors utilizing H3PMo12O40-modified carbon nanotubes are characterized by specific capacitances and energy densities on the levels of 40 F g−1 and 1.3 Wh kg−1, whereas the respective values for the systems built from bare carbon nanotubes are lower, 22 F g−1 and 0.7 Wh kg−1. It is reasonable to expect that fast and reversible multi-electron transfers of the Keggin-type H3PMo12O40 account for the pseudocapacitance effect and significantly contribute to the observed overall capacitance.  相似文献   

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