[Show abstract][Hide abstract] ABSTRACT: 3D NiχCo1−χ oxides with different morphologies for high-capacity supercapacitors were controllably synthesized via an electrodeposition method combined with a simple post annealing process. The synthesis involves the co-electrodeposition of the bimetallic (Ni, Co) hydroxide precursor on a nickel foam scaffold and subsequent thermal transformation to NiχCo1−χ oxides. The crystalline structure, morphology and electrochemical performance of the 3D NiχCo1−χ oxides can be readily manipulated by simply varying the Co/Ni molar ratio in the electrodeposition electrolyte. With the increase of the Co/Ni molar ratio, the characteristic peak intensities and the signal sites were gradually changed from a NiO crystal dominant structure to NiCo2O4 and finally to a Co3O4 dominant structure. Moreover, the morphology also can be controlled by adjusting the Co/Ni molar ratio in the electrodeposition electrolyte. In addition, the Ni0.61Co0.39 oxide electrode shows a large specific capacitance of 1523.0 F g−1 at 2 A g−1 and 95.30% of that can be retained, even at a high current density of 30 A g−1. The superior rate capability should be attributed to the unique 3D network-like architecture, which can enlarge the liquid–solid interfacial area, facilitate the electron and ion transport, and further increase the utilization of the active material. To demonstrate its practical application, an asymmetric supercapacitor based on the Ni0.61Co0.39 oxide electrode as a positive electrode and activated carbon as a negative electrode was fabricated. Owing to the outstanding capacitive behavior of the Ni0.61Co0.39 oxide electrode, the asymmetric device delivers a prominent energy density of 36.46 W h kg−1 at a power density of 142 W kg−1, and which holds great promise for potential applications in energy storage.
[Show abstract][Hide abstract] ABSTRACT: A novel MnO2/graphene (G)/nickel foam (NF) composite as supercapacitor electrode was fabricated by a facile electrochemical deposition approach for the first time. The approach includes electrophoretic deposition of G on NF (EPD-G/NF) and electrodeposition of MnO2 on EPD-G/NF (MnO2/EPD-G/NF). Compared with other methods for preparing MnO2/G composite, our green strategy avoids using harsh chemicals (e.g. hydrazine) or high temperature treatment for reducing graphene oxide. Owing to unique structure, specific capacitance (Cs) of the MnO2/EPD-G/NF electrode is as high as 476 F g− 1 at high current density of 1 A g− 1 in 0.5 M Na2SO4 solution, which is the highest Cs for MnO2/G composites to date, and the Cs is higher than that of MnO2/NF electrode. Furthermore, it also exhibits high rate capacity, such as 216 F g− 1 of Cs at 10 A g− 1. On the other hand, our strategy provides a versatile method for fabrication of other G-based composites with metal oxide/hydroxide or conducting polymer as supercapacitor electrode.
[Show abstract][Hide abstract] ABSTRACT: The effect of the electrodeposition temperature on the electrochemical performance of Ni(OH)2electrode was investigated in this report. Ni(OH)2 was electrodeposited directly on nickel foam at different temperatures. The crystalline structure, morphology and specific surface area of the prepared Ni(OH)2 were characterized by X-ray powder diffraction (XRD), field emission scanning electronic microscopy (FESEM) and Brunauer–Emmett–Teller (BET). Electrochemical techniques such as cyclic voltammetry (CV), chronopotentiometry, and electrochemical impedance spectra (EIS) were carried out to systematically study the electrochemical performance of various Ni(OH)2electrodes in 1 M KOH electrolyte. The results demonstrated that the electrodeposition temperature had obviously affected the properties of the Ni(OH)2. A pure α-Ni(OH)2 phase could be observed at low temperature. When the temperature increased to 65 °C, the β-Ni(OH)2 phase together with α-Ni(OH)2 phase were present. Moreover, the sample synthesized at 65 °C possessed a porous honeycomb-like microstructure and the corresponding specific capacitance was up to 3357 F g−1 at a charge–discharge current density of 4 A g−1, which suggested its potential application as an electrode material for supercapacitors.
[Show abstract][Hide abstract] ABSTRACT: Nanodiamond (ND)/poly (lactic acid) (PLA) nanocomposites with potential for biological and biomedical applications were prepared by using melting compound methods. By means of transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analyses (TGA), Dynamic mechanical analyses (DMA), Differential scanning calorimetry (DSC) and Tensile test, the ND/PLA nanocomposites were investigated, and thus the effect of ND on the structural, thermal and mechanical properties of polymer matrix was demonstrated for the first time. Experimental results showed that the mechanical properties and thermal stability of PLA matrix were significantly improved, as ND was incorporated into the PLA matrix. For example, the storage modulus (E′) of 3wt% ND/PLA nanocomposites was 0.7GPa at 130°C which was 75% higher than that of neat PLA, and the initial thermal decomposition was delayed 10.1°C for 1wt% ND/PLA nanocomposites compared with the neat PLA. These improvements could be ascribed to the outstanding physical properties of ND, homogeneous dispersion of ND nanoclusters, unique ND bridge morphology and good adhesion between PLA matrix and ND in the ND/PLA nanocomposites.
Composites Part B Engineering 12/2010; 41(8):646-653. · 2.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To improve the performance of direct ethanol fuel cells (DEFCs), a three-dimensional (3D), hierarchically structured Pd electrode has been successfully fabricated by directly electrodepositing Pd nanoparticles on the nickel foam (referred as Pd/Nickel foam electrode hereinafter). The electrochemical properties of the as-prepared electrode for ethanol oxidation have been investigated by cyclic voltammetry (CV). The results show that the oxidation peak current density of the Pd/Nickel foam electrode is 107.7 mA cm−2, above 8 times than that of Pd film electrode at the same Pd loading (0.11 mg cm−2), and a 90 mV negative shift of the onset potential is found on the Pd/Nickel foam electrode compared with the Pd film electrode. Furthermore, the peak current density of the 500th cycle remains 98.1% of the maximum value for the Pd/Nickel foam electrode after a 500-cycle test, whereas it is only 14.2% for the Pd film. The improved electrocatalytic activity and excellent stability of the Pd/Nickel foam electrode make it a favorable platform for direct ethanol fuel cell applications.
Journal of Power Sources 10/2010; 195(19):6496-6499. · 5.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Silkworm silk/Poly(lactic acid) (silk/PLA) biocomposites with potential for environmental engineering applications were prepared by using melting compound methods. By means of Dynamic mechanical analysis (DMA), Differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA), Coefficient of thermal expansion test, Enzymatic degradation test and Scanning electron microscopy (SEM), the effect of silk fiber on the structural, thermal and dynamic mechanical properties and enzymatic degradation behavior of the PLA matrix was investigated. As silk fiber was incorporated into PLA matrix, the stiffness of the PLA matrix at higher temperature (70–160 °C) was remarkably enhanced and the dimension stability also was improved, but its thermal stability became poorer. Moreover, the presence of silk fibers also significantly enhanced the enzymatic degradation ability of the PLA matrix. The higher the silk fiber content, the more the weight loss.
Polymer Degradation and Stability 10/2010; · 2.63 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Two types of ordered mesoporous carbons (OMCs-FT and OMCs-F) with different hexagonal pore frameworks were synthesized via two soft template routes. Structural characterizations revealed that OMCs-FT possessed broader mesopore range, more enhanced mesoporosity and higher surface area, compared with the counterpart of OMCs-F. In order to systematically investigate the relationship between the pore characteristics and electrochemical performances, two catalysts of OMCs-FT/Pt and OMCs-F/Pt were achieved by ethylene glycol-assisted reduction procedure. X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements indicated that face-centered cubic Pt nanoparticles with an average size of 5.3nm were homogeneously deposited on OMCs-FT while the mean size of 5.5nm Pt nanoparticles had a relatively ransom dispersion on OMCs-F supports with some aggregations. The electrochemical results disclosed that OMCs-FT/Pt catalyst exhibited higher electrocatalytic activity and better stability than OMCs-F/Pt and commercially available E-TEK/Pt catalysts for methanol electro-oxidation. The broad mesopore range, enhanced mesoporosity and high surface area of OMCs-FT supports were considered to be the main reasons for its enhanced catalytic activity.
Journal of electroanalytical chemistry 08/2009; 633(1):1-6. · 2.87 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Functional sulfonic acid groups were covalently grafted onto the surface of multi-walled carbon nanotubes (MWNTS) via a facile route from sulfuric acid and acetic anhydride under mild conditions. The resulting sulfonated MWNTS (S-MWNTS) were further deposited with Pd nanoparticles (S-MWNTS/Pd) as catalysts for ethylene glycol electro-oxidation. Structural characterizations revealed that homogeneously dispersed Pd nanoparticles with an average size of 4.5nm were loaded on the S-MWNTS supports. It was found that S-MWNTS/Pd catalysts exhibited better electrocatalytic activity and long-term stability than the unsulfonated counterparts. In contrast to the common sulfonication approaches, our strategy could make the functionalization process more easily and effectively, in this way resulting in small size and uniform dispersion of Pd nanoparticles loaded onto the nanotube surfaces. All these demonstrate that it is a simple and efficient approach towards sulfonate-assisted surface functionalization.
Journal of Power Sources 06/2009; 191(2):366-370. · 5.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A novel supporting material containing benzenesulfonic acid (BSA) groups and ordered mesoporous carbons (OMCs) was first prepared by in situ radical polymerization of 4-styrenesulfonate and isoamyl nitrite under ambient conditions. Then, Pd nanoparticles were deposited on as-produced OMCs (f-OMCs) by the NaBH(4) reduction method. The structure and nature of the resulting composites were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and nitrogen adsorption-desorption. The results show that BSA groups are created and the texture and surface chemistry are altered, whereas the ordered porous structure is maintained. The electrocatalytic properties of the Pd/f-OMCs catalysts for formic acid oxidation (HCOOH) have been investigated by cyclic voltammetry and chronoamperometry methods, and excellent electrocatalytic activity can be observed.
Journal of Colloid and Interface Science 06/2009; 337(2):614-8. · 3.55 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 4-Aminobenzoic acid (4-ABA) was covalently grafted on to the surface of multiwalled carbon nanotubes (MWNTs) via a novel amine-cation induced radical reaction. Then, Pd nanoparticles were deposited on functional 4-ABA group-grafted MWNTs (F-MWNTs) by NaBH4 reduction method. The structure and nature of the resulting product were characterized by Fourier transform infrared (FT-IR) spectrometry, transmission electron microscopy (TEM), and X-ray diffraction (XRD) measurements. The electrocatalytic properties of the Pd/F-MWNTs catalyst for methanol oxidation have been investigated by cyclic voltammetry, linear sweep voltammetry and chronomperometry methods. In contrast to the unfunctionalized counterpart, the electrochemical results demonstrate that Pd/F-MWNTs exhibit better electrocatalytic activities and stability, mainly due to the uniform dispersion and small particle size of Pd nanoparticles on the F-MWNT supports. The results imply that the Pd/F-MWNTs catalyst shows the better electrocatalytic performances and has a promising application potential in fuel cells.
[Show abstract][Hide abstract] ABSTRACT: Polyaniline/multi-walled carbon nanotubes (MWNTs) composites were prepared by an in situ chemical oxidative polymerization method and were used as the cathode materials for rechargeable lithium batteries. The structure and morphology of the as-synthesized samples were investigated by X-ray diffraction (XRD) and transmission electron microscope (TEM). The charge/discharge property, coulombic efficiency, cyclic voltammetry and ac impedance spectroscopy of the as-prepared samples were also examined in detail. It was confirmed that MWNTs had an obvious effect on the electrochemical performance of polyaniline. The results could be attributed to the excellent electronic and electrochemical properties of MWNTs.
Materials Chemistry and Physics 03/2009; · 2.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A novel chemical method based on ultrasonic assisted polyol synthesis for the fabrication of highly dispersed Pt nanoparticles
on multi-walled carbon nanotubes (MWCNTs) was developed. The simple and green method took only about 10min at ambient temperature.
The structure and chemical nature of the resulting Pt/MWCNT composites were characterized by transmission electron microscopy
(TEM), X-ray diffraction (XRD), and energy dispersive X-ray spectrometry (EDS). The results showed that the prepared Pt nanoparticles
were uniformly dispersed on the MWCNT surface. The mean size of Pt nanoparticles was about 2.8nm. Electrochemical properties
of Pt/MWCNT electrode for methanol oxidation were examined by cyclic voltammetry (CV) and excellent electrocatalytic activities
could be observed. The possible formation mechanism of Pt/MWCNTs was also discussed.
Journal of Solid State Electrochemistry 02/2009; 13(3):371-376. · 2.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Novel ordered mesoporous cobalt hydroxide films have been successfully electrodeposited on different substrates, i.e., foamed nickel mesh and titanium plate, from cobalt nitrate dissolved in the aqueous domains of the hexagonal lyotropic liquid crystalline phase of Brij 56. Field emission scanning electron microscope (FESEM) and transmission electron microscopy (TEM) studies present that the as-deposited films have an interlaced nanosheet-like surface morphology and possess a regular nanostructure with hexagonal arrays of pores of nanometer dimension and extended periodicity. Various electrochemical test results show that the films on both substrates exhibit excellent electrochemical capacitive behavior due to the special ordered mesoporous nanostructure. Furthermore, it is obvious that the ordered mesoporous cobalt hydroxide film on foamed Ni mesh has much higher specific capacitance (maximum: 2646Fg−1) than that of the film on Ti plate (maximum: 1018Fg−1), which is mainly because that the foamed Ni mesh substrate with much larger surface area than Ti plate could enhance the utilization and the capacitance of Co(OH)2 film greatly.
Microporous and Mesoporous Materials 01/2009; 117(1):55-60. · 3.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Electrodeposited Ni(OH)(2) on nickel foam with porous and 3D nanostructures has ultrahigh capacitance in the potential range -0.05-0.45 V, and a maximum specific capacitance as high as 3152 F g(-1) can be achieved in 3% KOH solution at a charge/discharge current density of 4 A g(-1).
Chemical Communications 01/2009; · 6.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this work, we report a concise method to self-assemble Pd nanoparticles onto the surface of MWNTs. Highly dispersed palladium nanoparticles are loaded on the MWNTs functionalized with mercaptobenzene moieties. The structure of the resulting Pd–fMWNT composite were characterized by transmission electron microscopy (TEM), the results show that the chemically synthesized Pd nanoparticles were homogeneously dispersed and well-separated from one another on the functional MWNT surfaces. Cyclic voltammogram (CV) showed that Pd–fMWNT composite materials perform excellent electrocatalytic activity and long-term stability toward formaldehyde oxidation. Electrochemical impedance spectroscopy (EIS) revealed the strong interaction between fMWNTs and Pd facilitates the effective degree of electron dolocalization, and thus enhances the conductivity of the composite. The results imply that the self-organized Pd–fMWNT composite as a promising support material shows the excellent electrocatalytic activity and has a promising application potential in fuel cells and biosensors.
Journal of Power Sources 01/2009; 186(2):339-343. · 5.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Functionalized benzenesulfonic groups were grafted onto the surface of multi-walled carbon nanotubes (MWCNTs) supported Pd catalysts in direct methanol fuel cells by a new and simple in situ radical polymerization of 4-styrenesulfonate and isoamyl nitrite. The resultant sulfonated MWCNTs-supported Pd catalysts (S-MWCNTs/Pd) were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectrometry measurements. Electrochemical characterizations of S-MWCNTs/Pd catalysts for methanol electro-oxidation in alkaline solution were investigated by cyclic voltammetry techniques. These results showed that S-MWCNTs/Pd exhibited higher electrocatalytic activity, enhanced CO tolerance and better stable life than did that with the unsulfonated counterparts, mainly due to the easier access with methanol and well dispersed distribution of the S-MWCNTs/Pd catalysts in water. In addition, compared with traditional sulfonation of MWCNTs, this new approach is more advantageous to make small and uniform dispersion of Pd particles loaded onto the surfaces of sulfonated MWCNTs, indicating it is a simple, rapid, and efficient method to functionalize MWCNTs.
Journal of Power Sources 12/2008; · 5.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A novel conjunct template method for fabricating mesoporous Pt nanowire array through direct current (DC) electrodeposition of Pt into the pores of anodic aluminum oxide (AAO) template on Ti/Si substrate from hexagonal structured lyotropic liquid crystalline phase is demonstrated in this paper. The morphology and structure of as-prepared Pt nanowire array are characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The electrocatalytic properties of Pt nanowire array for methanol are also investigated in detail. The results indicate that Pt nanowire array has the unique mesoporous structure of approximate 40–50nm in diameter, which resulted in the high surface area and greatly improved electrocatalytic activity for methanol. The mesoporous Pt nanowire array synthesized by the new conjunct template method has a very promising application in portable fuel cell power sources.
[Show abstract][Hide abstract] ABSTRACT: Polystyrene–acrylonitrile mixed with different carbon nanotube (CNT) fractions has been successfully prepared by means of in situ polymerization method. The tribological behaviors of the nanocomposites are investigated by friction and wear tester under dry conditions. Compared with the polystyrene–acrylonitrile, polystyrene–acrylonitrile–CNTs shows not only the lower friction coefficient but also the higher wear resistance, which reveals that CNT could reduce the friction and improve the wear resistance behaviors of the nanocomposites dramatically. According to the results of the microhardness measurements, CNT is found to be able to improve the microhardness of the nanocomposites effectively. The mechanism of the reinforced tribological properties and microhardness for the polystyrene–acrylonitrile–CNTs nanocomposites is also discussed in detail.
[Show abstract][Hide abstract] ABSTRACT: Novel ordered mesoporous cobalt hydroxide film (designated HI-e Co(OH)2) has been successfully electrodeposited from cobalt nitrate dissolved in the aqueous domains of the hexagonal lyotropic liquid crystalline phase of Brij 56. Experimental electrodeposition parameters such as deposition potentials and deposition temperatures are varied to analyze their influences on the electrochemical capacitor behavior. The films are physically characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to determine the effects of deposition potentials and temperatures on the surface morphology and nanostructure. Electrochemical techniques such as cyclic voltammetry (CV) and chronopotentiometry are applied to systematically investigate the effects of deposition potentials and temperatures on the capacitance of the films. The results demonstrated that the capacitive performance of the HI-e Co(OH)2 film achieved the highest value when it is electrodeposited at −0.75V under the deposition temperature of 50°C.