56362045
Ionic liquid-assisted synthesis of a NiO/CNTs composite and its electrochemical capacitance
A novel solid-state method has been developed for synthesizing nickel oxide (NiO)/carbon nanotubes (CNTs) composite using an ionic liquid (IL, 1-butyl-3-methylimidazolium chloride) as the reaction medium. Ultraviolet-visible (UV-vis) absorbance spectroscopy, infrared spectroscopy (IR), and scanning electron microscopy (SEM) were employed to investigate the structure, morphology, and formation mechanism of the synthesized sample. The results demonstrated that the IL is effective for dispersing CNTs, which allows the tethering of nickel (II) ions onto the surfaces of the CNTs and facilitates the subsequent chemical deposition of NiO to obtain the NiO/CNTs composite. The electrochemical properties of the composite were determined using cyclic voltammetry and galvanostatic charge/discharge measurements in 6M KOH. Because of its unique structure, the prepared NiO/CNTs electrode exhibited good capacitive behavior and cyclability. The high specific capacitance (521 F g-1) and good rate capability (91% capacity retention at 0.5Ag-1) of the NiO/CNTs composite enable its use as a practical supercapacitor electrode material.
30629671
Large-scale synthesis of reduced graphene oxides with uniformly coated polyaniline for supercapacitor applications.
We report an effective route for the preparation of layered reduced graphene oxide (rGO) with uniformly coated polyaniline (PANI) layers. These nanocomposites are synthesized by chemical oxidative polymerization of aniline monomer in the presence of layered rGO. SEM, TEM, X-ray photoelectron spectroscopy (XPS), FTIR, and Raman spectroscopy analysis results demonstrated that reduced graphene oxide-polyaniline (rGO-PANI) nanocomposites are successfully synthesized. Because of synergistic effects, rGO-PANI nanocomposites prepared by this approach exhibit excellent capacitive performance with a high specific capacitance of 286 F g(-1) and high cycle reversibility of 94 % after 2000 cycles.
37634546
Electric double-layer capacitors based on highly graphitized nanoporous carbons derived from ZIF-67.
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 sp(2) -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.
23996055
Direct growth of cobalt hydroxide rods on nickel foam and its application for energy storage.
The present work reports synthesis of cobalt hydroxide (Co(OH)2) rods on nickel foam and its supercapacitor application. Hierarchical Co(OH)2 rods with length of approximately 3.5 μm and diameter of approximately 400 nm were prepared by one-step, simple, and inexpensive chemical-bath-deposition method. The direct growth of Co(OH)2 rods on the Ni foam gave three dimensional (3D) structure for easy access of electrolyte throughout material surface. Also, well-adhered interface between Co(OH)2 rods and Ni-foam surface gave better conduction channels. Detailed electrochemical study was performed by using cyclic voltammetry and galvanostatic charge/discharge measurements. The results demonstrate that Co(OH)2 rods on Ni foam are efficient electrodes for supercapacitor application.
95496793
Sidewall Functionalization of Single-Walled Carbon Nanotubes with Nitrile Imines. Electron Transfer from the Substituent to the Carbon Nanotube
A new, versatile methodology for functionalization of single-walled carbon nanotubes (SWNTs), using 1,3-dipolar cycloaddition of nitrile imines to the sidewalls of SWNTs has been used to synthesize two soluble, photoactive single walled carbon nanotubes containing n-pentyl esters at the tips and 2,5-diarylpyrazoline units at the walls of the tubes. The success of the synthesis has been demonstrated by solution 1H and 19F NMR as well as UV−vis and FT-IR spectroscopy. These two compounds have been selected to have soluble single wall carbon nanotubes substituted either with an electron-poor 3,5-bis(trifluoromethyl)phenyl or electron-rich 4-(N,N-dimethylamino)phenyl on the C atom of the pyrazoline ring. Laser flash photolysis in dynamic flow of these carbon nanotubes in acetonitrile reveals the formation of several transient species decaying in the microsecond time scale. All the available data, including the photochemistry of model compounds, quenching experiments with electron donors and acceptors, and inf...
135590715
Nickel Oxide／Carbon Nanotubes Nanocomposite for Electrochemical Capacitance
A nanocomposite of nickel oxide/carbon nanotubes was prepared through a simple chemical precipitation followed by thermal annealing. The electrochemical capacitance of this electrode material was studied. When the mass fraction of CNTs (carbon nanotubes) in NiO/CNT composites increases, the electrical resistivity of nanocomposites decreases and becomes similar to that of pure CNTs when it reaches 30%. The specific surface area of composites increases with increasing CNT mass fraction and the specific capacitance reaches 160 F/g under 10 mA/g discharge current density at CNT mass fraction of 10%.
95684941
Template-free synthesis of ordered mesoporous NiO/poly(sodium-4-styrene sulfonate) functionalized carbon nanotubes composite for electrochemical capacitors
We report the first example of a practical and efficient template-free strategy for synthesizing ordered mesoporous NiO/poly(sodium-4-styrene sulfonate) (PSS) functionalized carbon nanotubes (FCNTs) composites by calcining a Ni(OH)2/FCNTs precursor prepared by refluxing an alkaline solution of Ni(NH3)x2+ and FCNTs at 97 °C for 1 h. The morphology and structure were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Thermal decomposition of the precursor results in the formation of ordered mesoporous NiO/FCNTs composite (ca. 48 wt% NiO) with large specific surface area. Due to its enhanced electronic conductivity and hierarchical (meso- and macro-) porosity, composite simultaneously meets the three requirements for energy storage in electrochemical capacitors at high rate, namely, good electron conductivity, highly accessibleelectrochemical surface areas owing to the existence of mesopores, and efficient mass transport from the macropores. Electrochemical data demonstrated that the ordered mesoporous NiO/FCNTs composite is capable of delivering a specific capacitance (SC) of 526 F/g at 1 A/g and a SC of 439 F/g even at 6 A/g, and show a degradation of only ca. 6% in SC after 2000 continuous charge/discharge cycles.
98050153
High dispersion and electrochemical capacitive performance of NiO on benzenesulfonic functionalized carbon nanotubes
Abstract This work describes an effective method to synthesize structurally uniform composite of nickel oxide/benzenesulfonic functionalized multiwalled carbon nanotubes composite (NiO/f-MWCNTs) using benzenesulfonic MWCNTs as the substrate. Benzenesulfonic group here is bifunctional both for solubilizing MWCNTs into aqueous solution and for tethering Ni 2+ precursor onto MWCNTs surfaces to facilitate the follow-up chemical deposition of NiO by supplying surface binding and anchoring groups. The composite has a uniform surface dispersion and large coverage of NiO onto f-MWCNTs, which is characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscope, cyclic voltammetry and galvanostatic charge/discharge measurements. The NiO/f-MWCNTs composite improved the utilization of electrochemical capacitive materials and delivered capacity of 384 F/g at the constant current of 0.20 A/g due to f-MWCNTs as substrate.
98599134
Synthesis, characterization, and electrochemical capacitance of amino-functionalized carbon nanotube/carbon paper electrodes
Abstract Amino-functionalization of carbon nanotubes (CNTs) attached to carbon paper (CP) has been achieved using one synthesis protocol: (i) chemical oxidation, (ii) acyl chlorination, and (iii) amidation. The amidation reaction of the carboxylic groups in oxidized the CNT/CP hybrids enables the formation of terminal amino groups on the CNT sidewalls. The functionalized CNTs were characterized by Raman spectroscopy, X-ray photoelectron spectroscopy, Fourier transformed infrared spectroscopy, thermal programmed desorption, and N2 adsorption. The cyclic voltammetry curves of an amino-modified CNT-based capacitor showed a continuum of double-layer and pseudocapacitive behavior. The presence of surface oxides and amides on CNTs imparts not only hydrophilic coverage for the formation of double-layer (double-layer capacitance) but also active sites for the redox reaction (pseudocapacitance). Based on the result of the charge/discharge cycling test, the N-modified CNT/CP capacitor exhibits an enhanced capacitance, high-rate capability, and capacitance stability with high coulombic efficiency.
95009653
An efficient route towards the covalent functionalization of single walled carbon nanotubes
Abstract A simple and efficient method of chemical functionalization of both single and multiwalled carbon nanotubes has been discussed to give enhanced water solubility by rapidly and efficiently generating an appreciable amount of hydrophilic functional groups using microwave radiation. Surface functionalization containing more than 30 wt% of oxygen has been achieved, resulting into solubility of 2–5 mg/mL. Further covalent functionalization of such soluble SWNTs provides a remarkable degree of aniline functionalization through amidation, where the formation of polyaniline has been avoided. Functionalization of SWNTs is confirmed by techniques like electron microscopy, Fourier transform infrared spectroscopy, thermogravimetry, Raman spectroscopy, cyclic voltammetry and impedance spectroscopy. Electrochemical analysis suggests an enhanced double layer capacitance (∼110 F/g) of nanotubes after microwave treatment. Aniline functionalization of SWNTs shows possible variations on the nanotube topography with concomitant formation of a dynamic polymer layer on the nanotube surface.
26104172
Functionalization of carbon nanotubes by an ionic-liquid polymer: dispersion of Pt and PtRu nanoparticles on carbon nanotubes and their electrocatalytic oxidation of methanol.
Small beginnings: Metal nanoparticle/CNT nanohybrids are synthesized from carbon nanotubes (CNTs) functionalized with an ionic-liquid polymer. The Pt and PtRu nanoparticles with narrow size distribution (average diameter: (1.3+/-0.4) nm for PtRu, (1.9+/-0.5) nm for Pt) are dispersed uniformly on the CNTs (see images) and show good performance in methanol electrooxidation.
26301897
Ultralight multiwalled carbon nanotube aerogel.
Ultralight multiwalled carbon nanotube (MWCNT) aerogel is fabricated from a wet gel of well-dispersed pristine MWCNTs. On the basis of a theoretical prediction that increasing interaction potential between CNTs lowers their critical concentration to form an infinite percolation network, poly(3-(trimethoxysilyl) propyl methacrylate) (PTMSPMA) is used to disperse and functionalize MWCNTs where the subsequent hydrolysis and condensation of PTMSPMA introduces strong and permanent chemical bonding between MWCNTs. The interaction is both experimentally and theoretically proven to facilitate the formation of a MWCNT percolation network, which leads to the gelation of MWCNT dispersion at ultralow MWCNT concentration. After removing the liquid component from the MWCNT wet gel, the lightest ever free-standing MWCNT aerogel monolith with a density of 4 mg/cm(3) is obtained. The MWCNT aerogel has an ordered macroporous honeycomb structure with straight and parallel voids in 50-150 μm separated by less than 100 nm thick walls. The entangled MWCNTs generate mesoporous structures on the honeycomb walls, creating aerogels with a surface area of 580 m(2)/g which is much higher than that of pristine MWCNTs (241 m(2)/g). Despite the ultralow density, the MWCNT aerogels have an excellent compression recoverable property as demonstrated by the compression test. The aerogels have an electrical conductivity of 3.2 × 10(-2) S·cm(-1) that can be further increased to 0.67 S·cm(-1) by a high-current pulse method without degrading their structures. The excellent compression recoverable property, hierarchically porous structure with large surface area, and high conductivity grant the MWCNT aerogels exceptional pressure and chemical vapor sensing capabilities.
95168255
Syntheses, Structures, and Properties of a Series of Metal Ion-Containing Dialkylimidazolium Ionic Liquids
A series of metal ion-containing ionic liquids [Bmim]2[MCl4] (M = Sn, Cu, Ni, Mn, Fe, Co, Zn, and Pt; [Bmim] = 1-butyl-3-methylimidazolium) and [Bmim]2[ZrCl6] were synthesized and their single-crys...
19275712
A cost-effective supercapacitor material of ultrahigh specific capacitances: spinel nickel cobaltite aerogels from an epoxide-driven sol-gel process.
Adv. Mater. 2010, 22, 347–351 2010 WILEY-VCH Verlag Gm The ever worsening energy depletion and global warming issues call for not only urgent development of clean alternative energies and emission control of global warming gases, but also more advanced energy storage and management devices. Supercapacitors, offering transient but extremely high powers, are probably the most important next generation energy storage device. To boost the specific capacitance of supercapacitors, the specific surface area of the electrode materials needs to be as high as possible to promote the electric double-layer capacitances and to accommodate a large amount of superficial electroactive species to participate in faradaic redox reactions. In addition, suitable pore sizes, 2–5 nm, of the porous electrode materials are critical to ease the mass transfer of electrolytes within the pores for fast redox reactions and double-layer charging/discharging. Aerogels are a class of mesoporous materials possessing highly specific surface areas and porosities, from which promising applications in a wide range of areas have been investigated. They are composed of 3D networks of nanoparticles with an average pore size of several nanometers, adjustably falling within the optimal pore sizes of 2–5 nm. Consequently, aerogels are a promising candidate for supercapacitor applications. As to the electrode material, electroactive materials possessing multiple oxidation states/structures that enable rich redox reactions for pseudocapacitance generation are desirable for supercapacitors. Transition metal oxides are such a class of materials that have drawn extensive and intensive research attention in recent years. Among them, RuO2 is themost prominent one with a specific capacitance as high as 1580F g , probably the highest ever reported. The commercialization of RuO2 based supercapacitors, however, is not promising because of the high cost and rareness of Ru. Spinel nickel cobaltite (NiCo2O4) is a low-cost, environmentally friendly transition metal oxide, which has been employed in electrocatalytic water splitting (oxygen evolution) and lithium ion batteries. Its application in supercapacitors, however, received much less attention. Nickel cobaltite has been reported to possess a much better electronic conductivity, at least two orders of magnitude higher, and higher electrochemical activity than those of nickel oxides and cobalt oxides. It is expected to offer richer redox reactions, including contributions from both nickel and cobalt ions, than the two corresponding single component oxides and is a potential cost-effective alternative for RuO2. Based on the above considerations, one would expect nickel cobaltite aerogels, with anticipated good electronic conductivity, low diffusion resistance to protons/cations, easy electrolyte penetration, and high electroactive areas to be a promising candidate for the construction of next-generation, ultrahighperformance supercapacitors. Traditionally, aerogels are prepared with sol–gel processes by taking corresponding alkoxides as the precursors. Alkoxides are generally expensive and sensitive to moisture and heat, requiring careful handling. Recently, to tackle these drawbacks, the epoxide synthetic route, enabling the use of low-cost and stable metal salts as the precursors, was successfully developed to prepare metal oxide aerogels. In this work, we reported the first successful preparation of nickel cobaltite aerogels with the epoxide-driven sol–gel process. The effects of the post-gel-drying calcination temperature on the critical properties of the product aerogels were investigated. At a starting Ni/Co ratio of 0.5 and a post-gel-drying calcination temperature of 200 8C, an optimal combination of composition, crystallinity, specific surface area, pore volume, and pore size was achieved to afford the nickel cobaltite aerogels that showed an extremely high-specific capacitance of 1400 F g 1 under a mass loading of 0.4 mg cm 2 at a sweep rate of 25mV s 1 within a potential window of 0.04 to 0.52V in a 1 M NaOH solution. The excellent reversibility and cycle stability of the product aerogels were also demonstrated. A stoichiometric mixture of nickel and cobalt chlorides was used as the precursor for the preparation of the nickel cobaltite aerogels. After the gel is dried in supercritical carbon dioxide, a post-gel-drying calcination is generally required to acquire preferred composition and/or better crystallinity of the products. The post-gel-drying calcination temperature is thus an important processing parameter to be studied. For referring convenience, we term the product aerogels as Ni–Co–O–T, with Tdenoting the calcination temperature. The T block is omitted for as-prepared samples. Also, for comparison purposes, NiO and Co3O4 aerogels were prepared, termed as Ni–O–T and Co–O–T, respectively. Figure 1a shows the X-ray diffraction (XRD) patterns of the as-prepared product aerogels and those samples calcined at 200 and 300 8C. Surprisingly, nickel cobaltite was formed even at the as-prepared condition. The diffraction peak located at the 2u value
97670488
A General and Efficient Route to Fabricate Carbon Nanotube‐Metal Nanoparticles and Carbon Nanotube‐Inorganic Oxides Hybrids
Novel pyrenyl-moieties-decorated hyperbranched polyglycidol (pHBP) is synthesized and utilized for the functionalization of carbon nanotubes (CNTs) via a non-covalent (non-destructive) process. Mediated by a pHBP layer on the CNT sidewall, Au, Ag and Pt nanoparticles and uniform SiO 2 , GeO 2 and TiO 2 coatings are generated in situ and deposited onto the as-prepared CNT/ pHBP hybrids, forming versatile homogeneous CNT-based nanohybrid sols. The coverage of metal nanoparticles and oxide coatings is controllable simply by changing the employed amount of precursors. This easy synthetic strategy provides a general and convenient route to efficiently assemble a wide range of metal nanoparticles and inorganic oxide components on the sidewalls of CNTs, and enables the construction of heterogeneous nanostructures with novel functionalities. As a means of demonstrating the versatility of the fabricated hybrid materials, the catalytic function of CNT/pHBP/Pt hybrids towards the reduction of 4-nitrophenol and the incorporation of dye molecules into the CNT/pHBP/SiO 2 matrix resulting in fluorescent nanofibers are investigated.
9522188
Carbon Nanotubes--the Route Toward Applications
Many potential applications have been proposed for carbon nanotubes, including conductive and high-strength composites; energy storage and energy conversion devices; sensors; field emission displays and radiation sources; hydrogen storage media; and nanometer-sized semiconductor devices, probes, and interconnects. Some of these applications are now realized in products. Others are demonstrated in early to advanced devices, and one, hydrogen storage, is clouded by controversy. Nanotube cost, polydispersity in nanotube type, and limitations in processing and assembly methods are important barriers for some applications of single-walled nanotubes.
12255375
A general strategy to layered transition-metal hydroxide nanocones: tuning the composition for high electrochemical performance.
A general and facile strategy for the synthesis of a large family of monometallic (Co, Ni) and bimetallic (Co-Ni, Co-Cu and Co-Zn) hydroxide nanocones (NCs) intercalated with DS ions is demonstrated. The basal spacing of the NCs can be varied by adjusting the intercalated DS amount. Especially, electrochemical characterizations reveal that bimetallic Co-Ni hydroxide NCs have a higher specific capacitance than their monometallic counterpart. These results suggest the importance of rational designing layered hydroxide NCs with tuned transition-metal composition for high-performance energy storage devices.
97919796
Preparation of silica aerogel using ionic liquids as solvents
Ionic liquids have been used as effective solvents to 
synthesize aerogels; a long aging time can be used to produce stable 
aerogel structures without the need for supercritical drying processes.