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1.
Nitrogen‐doped porous carbon nanotubes@MnO2 (N‐CNTs@MnO2) nanocomposites are prepared through the in situ growth of MnO2 nanosheets on N‐CNTs derived from polypyrrole nanotubes (PNTs). Benefiting from the synergistic effects between N‐CNTs (high conductivity and N doping level) and MnO2 nanosheets (high theoretical capacity), the as‐prepared N‐CNTs@MnO2‐800 nanocomposites show a specific capacitance of 219 F g?1 at a current density of 1.0 A g?1, which is higher than that of pure MnO2 nanosheets (128 F g?1) and PNTs (42 F g?1) in 0.5 m Na2SO4 solution. Meanwhile, the capacitance retention of 86.8 % (after 1000 cycles at 10 A g?1) indicates an excellent electrochemical performance of N‐CNTs@MnO2 prepared in this work.  相似文献   

2.
Disha Soni  Rahul Pal 《Electroanalysis》2016,28(9):1951-1956
Phase pure nanocrystalline manganese iron oxide [(Mn0.37Fe0.63)2O3] was synthesized by combustion technique based on propellant chemistry principle employing citric acid as fuel. The synthesized powder was characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), BET, BJH analysis and electrochemical studies for possible application as a charge storage electrode. The average crystallite size was found to be 18.6 nm from XRD analysis. BET analysis yielded the surface area and specific pore volume of the powder to be 22.96 m2 g?1 and 0.0098 cm3 g?1 respectively. The specific capacitance from cyclic voltammetric studies at scan rate 5 mV s?1 was found to be about 30 F g?1 cm?2 while from charge discharge studies was found to be 27±1 F g?1 cm?2. In addition, the material showed appreciable stability during charge‐discharge cycling.  相似文献   

3.
For the first time, hierarchically porous carbon materials with a sandwich‐like structure are synthesized through a facile and efficient tri‐template approach. The hierarchically porous microstructures consist of abundant macropores and numerous micropores embedded into the crosslinked mesoporous walls. As a result, the obtained carbon material with a unique sandwich‐like structure has a relatively high specific surface (1235 m2 g?1), large pore volume (1.30 cm3 g?1), and appropriate pore size distribution. These merits lead to a comparably high specific capacitance of 274.8 F g?1 at 0.2 A g?1 and satisfying rate performance (87.7 % retention from 1 to 20 A g?1). More importantly, the symmetric supercapacitor with two identical as‐prepared carbon samples shows a superior energy density of 18.47 Wh kg?1 at a power density of 179.9 W kg?1. The asymmetric supercapacitor based on as‐obtained carbon sample and its composite with manganese dioxide (MnO2) can reach up to an energy density of 25.93 Wh kg?1 at a power density of 199.9 W kg?1. Therefore, these unique carbon material open a promising prospect for future development and utilization in the field of energy storage.  相似文献   

4.
The present work is about the preparation of silver (Ag)-doped manganese oxide (MnO2)/graphene oxide (GO) composite thin films are deposited by a facile and binder-free successive ionic layer adsorption and reaction (SILAR) method for the first time. The Brunauer-Emmett-Teller (BET) study revealed the nanosheets of MnO2–Ag3/GO exhibit high specific surface area of 192 m2 g?1. The tailored flower-like morphology and interconnected nanosheets of MnO2–Ag3/GO electrodes achieved high electrochemical performance. The maximum specific capacitance (Cs) of 877 F g?1 at the scan rate of 5 mV s?1 is obtained for MnO2–Ag3/GO electrode tested in 1 M sodium sulfate (Na2SO4) electrolyte with capacity retention of 94.57% after 5000 cycling stability. The MnO2–Ag3/GO composite-based flexible solid state symmetric supercapacitor (FSS-SSC) device delivered Cs as 164 F g?1 with specific energy of 57 Wh kg?1 at specific power of 1.6 kW kg?1 and capacitive retention of 94% after 10,000 cycles.  相似文献   

5.
A hierarchical hollow hybrid composite, namely, MnO2 nanosheets grown on nitrogen‐doped hollow carbon shells (NHCSs@MnO2), was synthesized by a facile in situ growth process followed by calcination. The composite has a high surface area (251 m2g?1) and mesopores (4.5 nm in diameter), which can efficiently facilitate transport during electrochemical cycling. Owing to the synergistic effect of NHCSs and MnO2, the composite shows a high specific capacitance of 306 F g?1, good rate capability, and an excellent cycling stability of 95.2 % after 5000 cycles at a high current density of 8 A g?1. More importantly, an asymmetric supercapacitor (ASC) assembled by using NHCSs@MnO2 and activated carbon as the positive and negative electrodes exhibits high specific capacitance (105.5 F g?1 at 0.5 A g?1 and 78.5 F g?1 at 10 A g?1) with excellent rate capability, achieves a maximum energy density of 43.9 Wh kg?1 at a power density of 408 W kg?1, and has high stability, whereby the ASC retains 81.4 % of its initial capacitance at a current density of 5 A g?1 after 4000 cycles. Therefore, the NHCSs@MnO2 electrode material is a promising candidate for future energy‐storage systems.  相似文献   

6.
通过在两种商品活性炭XC-72(比表面250m2·g-1)和YEC-8(比表面1726m·2g-1)电极表面涂刷Mn(NO3)2,并在200℃进行热分解得到表面担载氧化锰的复合材料电极.采用扫描电子显微镜(SEM)和X射线衍射(XRD)表征电极的形貌和氧化锰的晶体结构,采用循环伏安、恒流充放电和交流阻抗考察了不同电极的电化学电容性能.结果表明,Mn(NO3)2在200℃的热解产物是α-Mn2O3和α-Mn3O4的混合物.当C和MnOx的质量比为2∶1和9∶1时,XC-72/MnOx中氧化锰的比电容分别达到499和435F·g-1,YEC-8/MnOx中氧化锰的比电容分别达到554和606F·g-1,表明氧化锰的赝电容对电极比电容的贡献十分显著.  相似文献   

7.
The homogenous coating of poly (3,4-ethylenedioxythiophene) (PEDOT) on carbon nanotubes was realized by using functionalization of single-walled carbon nanotubes (SWNTs) in this study. Consequently, the PEDOT/functionalized SWNTs (PEDOT/F-SWNTs) composites, with size of around 100nm, which is much smaller than that of PEDOT, were prepared by the electrochemical method. Its small granule increased the active/nonactive mass ratio and reduced the ions diffusion length. Therefore, its specific capacitance of the composite was up to 200F g?1, which was remarkably greater than that of PEDOT. Furthermore, the PEDOT/F-SWNTs composites had very rapid charge/discharge ability with specific capacitance of 180F g?1 at scanning rate of 200mV s?1 and 170F g?1 at frequency of 1Hz, which is an important practical advantage. In addition, such composite had a good cycling performance and a wide potential window.  相似文献   

8.
The synthesis of nanoporous graphene by a convenient carbon nanofiber assisted self‐assembly approach is reported. Porous structures with large pore volumes, high surface areas, and well‐controlled pore sizes were achieved by employing spherical silica as hard templates with different diameters. Through a general wet‐immersion method, transition‐metal oxide (Fe3O4, Co3O4, NiO) nanocrystals can be easily loaded into nanoporous graphene papers to form three‐dimensional flexible nanoarchitectures. When directly applied as electrodes in lithium‐ion batteries and supercapacitors, the materials exhibited superior electrochemical performances, including an ultra‐high specific capacity, an extended long cycle life, and a high rate capability. In particular, nanoporous Fe3O4–graphene composites can deliver a reversible specific capacity of 1427.5 mAh g?1 at a high current density of 1000 mA g?1 as anode materials in lithium‐ion batteries. Furthermore, nanoporous Co3O4–graphene composites achieved a high supercapacitance of 424.2 F g?1. This work demonstrated that the as‐developed freestanding nanoporous graphene papers could have significant potential for energy storage and conversion applications.  相似文献   

9.
Here, carbon nanotube@N‐doped mesoporous carbon (CNT@N‐PC) composites were synthesized by using resorcinol‐formaldehyde resin as carbon source, ionic liquids (ILs) as template, and nitrogen sources and tetraethyl orthosilicate (TEOS) as assistant agent. The use of ILs‐modified CNT with nitrogen and TEOS facilitated the generation of a richer mesoporous structure. The obtained CNT@N‐PC was composed of a CNT core and mesoporous carbon particles around it. CNT@N‐PC showed a 3D network structure like “dewy cobwebs” and had a high surface area of 857 m2 g?1, uniform pore size distribution (3.0 nm), and suitable N content (4.9 at.%). When used as supercapacitor electrode, the CNT@N‐PC exhibited a high specific capacitance (244 F g?1 at 1 A g?1), good rate capability and favorable capacitance retention (92.5 % capacitive retention after 5000 cycles), demonstrating the potential for application in high‐performance supercapacitors.  相似文献   

10.
Ag-doped MnO2 pseudocapacitor electrodes with dendrite and foam-like structures were successfully produced for the first time using an electrodeposition method employing structure-directing agents, i.e., sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) acting through micelle formation at solid–liquid interfaces. Doping silver with MnO2 enhanced their electronic conductance. Controlling pseudocapacitor electrode morphologies with surfactants accelerated ion transport. The specific capacitance values of the Ag-doped MnO2 films produced with SDS and CTAB, measured in 0.5?M Na2SO4 at a scan rate of 5?mV?s?1 were 551 and 557?F?g?1, respectively. These values are about 2.7-fold higher than that of the pure MnO2 film and about 1.4-fold higher than that of the Ag-doped MnO2 film made without using surfactants.  相似文献   

11.
The reduced graphene oxide (RGO)/bisphenol A (BPA) composites were prepared by an adsorption‐reduction method. The composites are characterized by X‐ray diffraction (XRD), UV‐vis, thermogravimetric (TG) analysis, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM). The results confirm that BPA is adsorbed on the basal plane of RGO by π‐π stacking interaction. Furthermore, the electrochemical behaviors were evaluated by cyclic voltammetry, galvanostatic charge/discharge techniques and electrochemical impedance spectroscopy (EIS). The results show that the RGO/BPA nanocomposites exhibit ultrahigh specific capacitance of 466 F·g?1 at a current density of 1 A·g?1, excellent rate capability (more than 81% retention at 10 A·g?1 relative to 1 A·g?1) and superior cycling stability (90% capacitance decay after 4000 cycles). Consequently, the RGO/BPA nanocomposites can be regarded as promising electrode materials for supercapacitor applications.  相似文献   

12.
Hierarchical mesoporous carbon materials with large microporosity were prepared by direct tri-constituent co-assembly with the use of resols as the carbon precursor, tetraethyl orthosilicate as the inorganic precursor, and triblock copolymer F127 as the soft template. Bimodal pore size distributions in the range of 1.5–4 and 7.5–12 nm were obtained in the synthesized hierarchical mesoporous carbon materials after etching of silica by HF acid, showing a high surface area of 1,675 m2?g?1 with a large pore volume of 2.06 cm3?g?1. The electrochemical performance of the hierarchical mesoporous carbons was evaluated as an electrode material for electrochemical supercapacitor, showing a specific capacitance as high as 152 F?g?1 at a scan rate of 5 mV?s?1 in 6 M KOH aqueous solution and a good cycling stability with capacitance retention of 99 % over 500 cycles.  相似文献   

13.
Nanoporous carbons (NPCs) have large specific surface areas, good electrical and thermal conductivity, and both chemical and mechanical stability, which facilitate their use in energy storage device applications. In the present study, highly graphitized NPCs are synthesized by one‐step direct carbonization of cobalt‐containing zeolitic imidazolate framework‐67 (ZIF‐67). After chemical etching, the deposited Co content can be completely removed to prepare pure NPCs with high specific surface area, large pore volume, and intrinsic electrical conductivity (high content of sp2‐bonded carbons). A detailed electrochemical study is performed using cyclic voltammetry and galvanostatic charge–discharge measurements. Our NPC is very promising for efficient electrodes for high‐performance supercapacitor applications. A maximum specific capacitance of 238 F g?1 is observed at a scan rate of 20 mV s?1. This value is very high compared to previous works on carbon‐based electric double layer capacitors.  相似文献   

14.
Nickel oxide nanosheets have been successfully synthesized by a facile ethylene glycol mediated hydrothermal method. The morphology and crystal structure of the nickel oxide nanosheets were characterized by X‐ray diffraction, field‐emission SEM, and TEM. When applied as electrode materials for lithium‐ion batteries and supercapacitors, nickel oxide nanosheets exhibited a high, reversible lithium storage capacity of 1193 mA h g?1 at a current density of 500 mA g?1, an enhanced rate capability, and good cycling stability. Nickel oxide nanosheets also demonstrated a superior specific capacitance of 999 F g?1 at a current density of 20 A g?1 in supercapacitors.  相似文献   

15.
Crosslinked-polyaniline (CPA) nano-pillar arrays adsorbed on the surface of reduced graphene oxide (RGO) sheets were synthesized by in situ solution polymerization through two steps of reduction. The electrochemical analyses demonstrated that the befittingly reduced CPA/RGO composite exhibited high performance as electrode materials for supercapacitors. The CPA/RGO composite showed very high specific capacitance of 1532 F g?1 at a scan rate of 10 mV s?1 or 694 F g?1 at a current density of 2 A g?1 in 1 M H2SO4 electrolyte, as well as great energy density of 61.4 W h kg?1 at a current density of 2 A g?1. The electrode material also had decent power density of 4 kW kg?1 at a current density of 10 A g?1, and good cycling stability of 92.5 % capacitance retained after 500 cycles of cyclic voltammetry at 500 mV s?1. The neat microstructures and super electrochemical properties suggest the potential use of the composites in supercapacitors.  相似文献   

16.
Three‐dimensional hierarchical porous graphene/carbon composite was successfully synthesized from a solution of graphene oxide and a phenolic resin by using a facile and efficient method. The morphology, structure, and surface property of the composite were investigated intensively by a variety of means such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption, Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR). It is found that graphene serves as a scaffold to form a hierarchical pore texture in the composite, resulting in its superhigh surface area of 2034 m2g?1, thin macropore wall, and high conductivity (152 S m?1). As evidenced by electrochemical measurements in both EMImBF4 ionic liquid and KOH electrolyte, the composite exhibits ideal capacitive behavior, high capacitance, and excellent rate performance due to its unique structure. In EMImBF4, the composite has a high energy density of up to 50.1 Wh kg?1 and also possesses quite stable cycling stability at 100 °C, suggesting its promising application in high‐temperature supercapacitors. In KOH electrolyte, the specific capacitance of this composite can reach up to an unprecedented value of 186.5 F g?1, even at a very high current density of 50 A g?1, suggesting its prosperous application in high‐power applications.  相似文献   

17.
Mesoporous manganese oxides (MnO2) were synthesized via a facile chemical deposition strategy. Three kinds of basic precipitants including sodium carbonate (Na2CO3), sodium bicarbonate (NaHCO3), and sodium hydroxide (NaOH) were employed to adjust the microstructures and surface morphologies of MnO2 materials. The obtained MnO2 materials display different microstructures. Great differences are observed in their specific surface area and porosity properties. The microstructures and surface morphologies characteristics of MnO2 materials largely determine their pseudocapacitive behavior for supercapacitors. The MnO2 prepared with Na2CO3 precipitant exhibits the optimal microstructures and surface morphologies compared with the other two samples, contributing to their best electrochemical performances for supercapacitors when conducted either in the single electrode tests or in the capacitor measurements. The optimal MnO2 electrode exhibits a high specific capacitance (173 F g–1 at 0.25 A g?1), high-rate capability (123 F g?1 at 4 A g?1), and excellent cyclic stability (no capacitance loss after 5,000 cycles at 1 A g?1). The optimal activated carbon//MnO2 hybrid capacitor exhibits a wide working voltage (1.8 V), high-power and high-energy densities (1,734 W kg?1 and 20.9 Wh kg?1), and excellent cycling behavior (93.8 % capacitance retention after 10,000 cycles at 1 A g?1), indicating the promising applications of the easily fabricated mesoporous MnO2 for supercapacitors.  相似文献   

18.
The development of high‐surface‐area carbon electrodes with a defined pore size distribution and the incorporation of pseudo‐active materials to optimize the overall capacitance and conductivity without destroying the stability are at present important research areas. Composite electrodes of carbon nano‐onions (CNOs) and polypyrrole (Ppy) were fabricated to improve the specific capacitance of a supercapacitor. The carbon nanostructures were uniformly coated with Ppy by chemical polymerization or by electrochemical potentiostatic deposition to form homogenous composites or bilayers. The materials were characterized by transmission‐ and scanning electron microscopy, differential thermogravimetric analyses, FTIR spectroscopy, piezoelectric microgravimetry, and cyclic voltammetry. The composites show higher mechanical and electrochemical stabilities, with high specific capacitances of up to about 800 F g?1 for the CNOs/SDS/Ppy composites (chemical synthesis) and about 1300 F g?1 for the CNOs/Ppy bilayer (electrochemical deposition).  相似文献   

19.
Porous nitrogen‐doped carbon nanotubes (PNCNTs) with a high specific surface area (1765 m2 g?1) and a large pore volume (1.28 cm3 g?1) have been synthesized from a tubular polypyrrole (T‐PPY). The inner diameter and wall thickness of the PNCNTs are about 55 nm and 22 nm, respectively. This material shows extremely promising properties for both supercapacitors and for encapsulating sulfur as a superior cathode material for high‐performance lithium–sulfur (Li‐S) batteries. At a current density of 0.5 A g?1, PNCNT presents a high specific capacitance of 210 F g?1, as well as excellent cycling stability at a current density of 2 A g?1. When the S/PNCNT composite was tested as the cathode material for Li‐S batteries, the initial discharge capacity was 1341 mAh g?1 at a current rate of 1 C and, even after 50 cycles at the same rate, the high reversible capacity was retained at 933 mAh g?1. The promising electrochemical energy‐storage performance of the PNCNTs can be attributed to their excellent conductivity, large surface area, nitrogen doping, and unique pore‐size distribution.  相似文献   

20.
A series of microporous carbons were prepared by simple carbonization and activation of phenol–melamine–formaldehyde resin. The morphology, surface area, and elemental composition of the samples were investigated by scanning electron microscope, Brunauer–Emmett–Teller measurement, Raman spectra, and elemental analysis, respectively. Electrochemical characteristics were evaluated by cyclic voltammograms, galvanostatic charge/discharge, and electrochemical impedance spectroscopy measurements in 6.0?mol?L?1 KOH. The microporous carbon activated by KOH presented a high specific capacitance of 202?F?g?1 at a scan rate of 2?mV?s?1. Furthermore, the KOH-activated microporous carbon electrode exhibited durable operation, the total loss of capacitance after 20,000 cycles is 2% at a current density of 500?mA?g?1. The good electrochemical performance of the activated carbon was ascribed to well-developed micropores, high surface area, larger pore volume as well as oxygen groups.  相似文献   

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