Nanofibers carbon

Kim et at deposited nano-thin PPy films on the vapor grown carbon fibers (VGCF) by using an in situ chemical oxidative polymerization of the monomer in the presence of FeCl oxidant by means of an ultrasonic 

Rakhi et al reported the conducting-polymers (polyaniline [PANI] and PPy)-coated carbon nanocoils (CNCs) as efficient binder-free electrode materials for supercapacitors for the first time, in which the CNCs acted as a perfect backbone for the uniform distribution of the conducting polymers in the composites [16]. Ihe SC and maximum storage energy per unit mass of the composites were found to be comparable to one of the best-reported values for polymer-coated MWNTs. Dumanli et al. prepared the chemically bonded carbon nanofibers (CNFs)-PPy composite via electro-polymerization of Py on CNFs [17]. It showed that the final capacitance values were highly dependent on the number of deposition cycles and deposition rates. The best result for the coiled CNF-PPy composite system was found to be 27.6 C/cm at six times cycling using 25 mV/s. 

Frackowiak s group coated PPy onto the multi-walled carbon nanotubes (MWNTs) via the chemical oxidative polymerization [18] or electropolymerization [19] to obtain the nanotubular composite materials for supercapacitors. Its SC reached 170 F/g in 1.0 mol/L H SO aqueous solution, about twice that given either by the nanotubes (80 F/g) or by the pure PPy (90 F/g). The author also claimed that a further treatment of the nanotubular materials, such as an oxidative treatment of the nanotubes or the deposition of PPy, was profitable for the enhancement of capacitance through pseudo-effects, however probably with a limited durability. However, in the cases the pseudo-capacitance by PPy was thought to be insufficiently utilized because of the thick and rigid structure and less entanglement of the MWNTs. 

Ryu et al. developed the mild and simple enzymatic catalysis of horseradish peroxidase (EC 1.11.1.7) in aqueous solutions (pH 4.0) to prepare 

Ham et al. prepared the PPy/SWNTs composites as an electrode in supercapadtor by the mini-emulsion polymerization of Py with sodium dodecylsulfate (SDS) as the surfactant [21]. Ihe CNT surfaces were partially enveloped with PPy. Ihe PPy/SWNTs composite electrode had larger SC as the weight fraction of SWNTs increased due to the more porous structure and the bare nanotube surfaces. 

With the increasing research interest in CNTs, carbon nanofibers were also investigated as anode material for LIBs. 

Various methods were adopted to fabricate carbon nanofibers with different performance for Li-ion insertion and extraction. High crystalline carbon nanofibers prepared by catal3 ic CVD presents high capacity (431 Relatively, crystalline carbon 

Electrospun polymers exhibit low levels of molecular defects, thus optimizing strength and creating order that leads to higher conductivity of 700 to 900 mS.cm 1 after carbonization at temperatures between 700 and 800°C [69]. The amorphous character of the CNFs allows effective functionalization and activation of fhe lowly graphitic form. Lowly graphitic PAN-based CNFs synfhesized by Kim et al. with steam activation (1100 m. g i) at 750°C showed 120 F.g i at 1 A.g i in KOH electrolyte [70]. They also showed that polyamic acid (PAA) fibers sfeam activated at 750°C (1400 m. g i), produced 160 F.g at 1 A.g i in KOH electrolyte [71]. 

Barranco et al. [69] electrospun CNF fibers by using a polymer blend containing a phenolic resin and a high density polyethylene (PE). The blend was carbonized at 800°C producing CNFs of 450 m2.g i (700 mS.cm ) and then KOH activated at 750°C to increase surface area to 1500 m2.g L The KOH activation reduced conductivity to 400 mS.cm but boosted capacitance to 180 F.g i (from 50 F.g i nof activafed) at 1 A.g (20 mA.cm in KOH electrolyte [69]. 

PANI nanoparticles uniformly coated the electrode and increased capacitance to 638 F.gr and maintained 90% capacitance after 1000 cycles [72]. 

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Surface Oxidation of Carbon Nanofibers Prior to Functionalization... 

Effect of oxidative treatments on catalytic property of carbon nanofiber composite... 

Dehydrogenation of ethylbenzene with carbon nanofiber supported iron oxide... 

Fig. 1(b) represents the selectivity to styrene as a ftmcfion of time fijr the above catal ts. It is observed that the selectivity to styrene is more than 95% over carbon nauofiber supported iron oxide catalyst compared with about 90% for the oxidized carbon nanofiber. It can be observed that there is an increase in selectivity to styrene and a decrease in selectivity to benzene with time on stream until 40 min. In particrdar, when the carbon nanofiber which has been treated in 4M HCl solution for three days is directly us as support to deposit the iron-precursor, the resulting catalyst shows a significantly lows selectivity to styrene, about 70%, in contrast to more than 95% on the similar catalyst using oxidized carbon nanofiber. The doping of the alkali or alkali metal on Fe/CNF did not improve the steady-state selectivity to styrene, but shortened the time to reach the steady-state selectivity. 

Oxidative dehydrogenation of propane over carbon nanofibers... 

A novel catalyst for PTA manufacture Carbon nanofiber supported palladium... 

Sonoelectrochemistry has also been used for the efficient employment of porous electrodes, such as carbon nanofiber-ceramic composites electrodes in the reduction of colloidal hydrous iron oxide [59], In this kind of systems, the electrode reactions proceed with slow rate or require several collisions between reactant and electrode surface. Mass transport to and into the porous electrode is enhanced and extremely fast at only modest ultrasound intensity. This same approach was checked in the hydrogen peroxide sonoelectrosynthesis using RVC three-dimensional electrodes [58]. 

Takenaka, S. et al., Methane decomposition into hydrogen and carbon nanofibers over supported Pd-Ni catalysts,. Catal., 220, 468,2003. 

Therefore, carbon nanofibers (CNFs) as well as carbon nanotubes (CNTs) were synthesized,18,19 functionalized (with the catalytic active metal Co), and finally... 

The multiwalled nanotubes as well as the herringbone type carbon nanofibers were synthesized in-house in a quartz glass fluidized bed reactor via chemical vapor deposition (CVD). The method is described in detail elsewhere.19 The platelet nanofibers, in contrast, were purchased from the company FutureCarbon GmbH (Bayreuth, Germany). 

FIGURE 2.1 Cobalt functionalized (a) platelet type carbon nanofibers, (b) herringbone type carbon nanofibers, and (c) carbon multiwalled nanotubes. 

Bezemer, G. L., Bitter, J. H., Kuipers, H. P. C. E., Oosterbeek, H., Holewijn, J. E., Xu, X. D., Kapteijn, F., van Dillen, A. J., and de Jong, K. P. 2006. Cobalt particle size effects in the Fischer-Tropsch reaction studied with carbon nanofiber supported catalysts. Journal of the American Chemical Society 128 3956-64. 

Yu, Z., Borg, 0., Chen, D., Enger, B. C., Frpseth, V., Rytter, E., Wigum, H., and Holmen, A. 2006. Carbon nanofiber supported cobalt catalysts for Fischer-Tropsch synthesis with high activity and selectivity. Catalysis Letters 109 43 -7. 

It has been observed that cobalt may undergo large-scale reconstruction under a synthesis gas environment.27 Reconstruction is a thermodynamically driven process that results in the stabilization of less reactive surfaces. Recent molecular modeling calculations have shown that atomic carbon can induce the clock reconstruction of an fee cobalt (100) surface.28 It has also been postulated and shown with in situ x-ray adsorption spectroscopy (XAS) on cobalt supported on carbon nanofibers that small particles (<6 nm) undergo a reconstruction during FTS that can result in decreased activity.29... 

Steigerwalt, S.E. et al., A Pt-Ru/graphitic carbon nanofiber nanocomposite exhibiting high relative performance as a direct-methanol fuel cell anode catalyst, J. Phys. Chem. B., 105, 8097, 2001. 

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