Tubular Carbon Nanofibers Research Articles

Synthesis and Characterization of Potassium Metal/Graphitic Carbon Nanofiber Intercalates

Direct reaction of herringbone, platelet, or narrow, tubular herringbone graphitic carbon nanofibers (GCNFs) with molten potassium gives K/GCNF intercalates with stoichiometric control of potassium loading. Intercalate formation is confirmed by powder X-ray diffraction and micro-Raman spectroscopy. K/GCNF intercalates act as radical-anion alkene polymerization catalysts and reduce water with stoichiometric formation of hydrogen gas. Stage-1 K/narrow, tubular GCNF intercalate exhibits thermionic emission at 300 °C. Stage-1 K/herringbone GCNF intercalate is an excellent thermionic emitter having high thermal stability up to 1000 °C. K/GCNF intercalates have much reduced work functions of ca. 2.2 eV with localized emission showing a work function of 1.6 eV.

Synthesis and Application of Quantum Dot-Tagged Fluorescent Microbeads

Direct reaction of herringbone, platelet, or narrow, tubular herringbone graphitic carbon nanofibers (GCNFs) with molten potassium gives K/GCNF intercalates with stoichiometric control of potassium loading. Intercalate formation is confirmed by powder X-ray diffraction and micro-Raman spectroscopy. K/GCNF intercalates act as radical-anion alkene polymerization catalysts and reduce water with stoichiometric formation of hydrogen gas. Stage-1 K/narrow, tubular GCNF intercalate exhibits thermionic emission at 300 degrees C. Stage-1 K/herringbone GCNF intercalate is an excellent thermionic emitter having high thermal stability up to 1000 degrees C. K/GCNF intercalates have much reduced work functions of ca. 2.2 eV with localized emission showing a work function of 1.6 eV.

Effect of binder content on the cycle performance of nano-sized Fe 2O 3-loaded carbon for use as a lithium battery negative electrode

Nano-sized Fe 2O 3-loaded carbon material was prepared by loading Fe 2O 3 on carbon using various carbonaceous materials. Carbonaceous materials strongly affected the electrochemical behavior of nano-sized Fe 2O 3-loaded carbon. In addition, the binder content also significantly affected the cycle performance of nano-sized Fe 2O 3-loaded carbon. The content of binder depended on the type of carbon used. In the optimal condition for binder content, nano-carbons such as acetylene black (AB), tubular carbon nanofibers (CNF), and platelet CNF provided larger capacities than graphite, and tubular CNF showed the greatest capacity after long-term cycling.

Effect of carbonaceous materials on electrochemical properties of nano-sized Fe 2O 3-loaded carbon as a lithium battery negative electrode

Nano-sized Fe 2O 3-loaded carbon material was prepared by loading Fe 2O 3 on carbon using various carbonaceous materials. Carbonaceous materials strongly affected the electrochemical behavior of nano-sized Fe 2O 3-loaded carbon. Among the carbons used, nano-carbons such as acetylene black (AB), tubular carbon nanofibers (CNF), and platelet CNF provided larger capacities than other carbons. This may be due to the greater surface area of nano-carbon, which gives a greater distribution of nano-sized Fe 2O 3 particles than other carbons and delivers a greater capacity than other carbons. Investigation of the first-cycle materials by X-ray photoelectron spectroscopy (XPS) revealed that Fe 2O 3 was reduced to Fe metal in the charge process (reduction of Fe 2O 3), and, conversely, Fe metal was not completely oxidized to Fe 2O 3 during discharge (oxidation of Fe). This result may be due to the covering of non-conductive Li 2O formed during charging.

Investigation of Carbon Nanofibers as Catalyst Support for Fuel Cell Electrodes

Cathodes for fuel cells with platinum as catalyst supported on tubular carbon nanofibers (CNFs) were investigated for the oxygen reduction reaction. CNFs should find a promising application field in fuel cell technology, due to their electrical and structural properties. CNFs were plated with platinum particles by an electroless plating method. CNF-based electrodes were produced by a sedimentation method. Polarization curves were measured in half cell tests, and physical characterization was carried out by scanning electron microscopy. It was shown that the fibers are capable of providing the required porosity with low binder content and an excellent electrical conductivity, as well as a good performance with low catalyst loading. The fibers allowed a reduction of the binder content in the electrode to prevent covering of catalyst with binder. With an optimization of the thickness of the electrode, the catalyst is lowered by 40 % without a significant loss of performance.

The effect of additives on the electrochemical properties of Fe/C composite for Fe/air battery anode

K 2S and FeS were employed as additives for electrolyte and electrode, respectively, to suppress hydrogen evolution and improve the cycleability of the Fe/C composite air battery anode. The effects of these additives on the electrochemical properties of Fe/C composite electrodes were investigated using cyclic voltammetry (CV). The results showed that both K 2S and FeS significantly suppressed hydrogen evolution on the Fe/C electrode characteristics. Among the carbons used, nano-carbons such as tubular carbon nanofibers (CNF), platelet CNF, vapor-grown carbon fibers (VGCF) and acetylene black (AB) improved the discharge capacity of the Fe/C electrode with additive to electrolyte or electrode. The FeS additive showed a larger beneficial effect for the Fe/C composite electrode than K 2S in term of cycleability and capacity.

The electrochemical properties of Fe 2O 3-loaded carbon electrodes for iron–air battery anodes

The redox efficiency of iron has been improved by increasing the distribution of iron on the carbon surface with Fe 2O 3-loaded carbon materials. The Fe 2O 3-loaded carbon material was prepared by loading Fe 2O 3 on carbon by a chemical method. Fe(NO 3) 3 was impregnated on carbon with different weight ratios of iron-to-carbon in an aqueous solution, and the mixture was dried and then calcined for 1 h at 400 °C in flowing Ar. The effect of various carbons on the physical and electrochemical properties of Fe 2O 3-loaded carbon electrodes was investigated with the use of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) along with X-ray energy-dispersive spectroscopy (EDS), cyclic voltammetry (CV) and galvanostatic cycling performance. Transmission electron microscopy coupled with X-ray diffraction measurements revealed that small Fe 2O 3 particles were distributed on the carbon surface. Natural graphite and several nano-carbon materials such as acetylene black and tubular carbon nanofibers (tubular CNF) exhibited improved characteristics, such as enhanced capacity and higher redox currents for the Fe 2O 3-loaded carbon electrode. SEM and EDS results suggest that Fe 2O 3-loaded nano-carbon electrodes, due to the large surface area of the nano-carbon, have more Fe 2O 3 dispersed than on Fe 2O 3-coated graphite electrodes.

The effect of carbon species on the properties of Fe/C composite for metal–air battery anode

For the purpose of finding an adequate carbon additive for a Fe/C composite air battery anode, effects of various carbons on the electrochemical properties of Fe/C composite electrodes were investigated using cyclic voltammetry (CV) and scanning electron microscopy (SEM), together with X-ray energy-dispersive spectroscopy (EDS). Acetylene black, tubular carbon nanofiber (CNF) and platelet CNF exhibited good results, including improved conductivity and higher redox currents of the Fe/C electrode. EDS revealed that on the Fe/nano-carbon surface, especially on the Fe/tubular CNF surface, iron was more dispersed than on Fe/graphite after cycling. Such a high dispersion of iron on nano-carbon surfaces may improve the electrochemical behavior of the Fe redox species.

High yield preparation of tubular carbon nanofibers over supported Co?Mo catalysts

In the search for high yield synthesis of carbon nanotubes (CNTs) at lower temperatures, Co–Mo catalysts on carbon black were investigated with ethylene and CO as carbon sources in catalytic gas-phase pyrolysis in comparison to that on TiO 2 . The carbon black support was expected to be advantageous because of the feasibility of a CNT/carbon black composite possibly fabricated for several applications without removal of the support. Depending on the catalyst support, the catalytic activity toward CO and ethylene showed great differences. Co–Mo (9:1) catalysts on titania or carbon black provided a high carbon yield from CO and ethylene at the rather low temperatures of 450–530 °C.

High yield preparation of tubular carbon nanofibers over supported Co–Mo catalysts

In the search for high yield synthesis of carbon nanotubes (CNTs) at lower temperatures, Co–Mo catalysts on carbon black were investigated with ethylene and CO as carbon sources in catalytic gas-phase pyrolysis in comparison to that on TiO 2. The carbon black support was expected to be advantageous because of the feasibility of a CNT/carbon black composite possibly fabricated for several applications without removal of the support. Depending on the catalyst support, the catalytic activity toward CO and ethylene showed great differences. Co–Mo (9:1) catalysts on titania or carbon black provided a high carbon yield from CO and ethylene at the rather low temperatures of 450–530 °C.

Pt−Ru/Carbon Fiber Nanocomposites: Synthesis, Characterization, and Performance as Anode Catalysts of Direct Methanol Fuel Cells. A Search for Exceptional Performance

Six Pt−Ru/carbon fiber nanocomposites have been prepared by using a bimetallic precursor as a source of metal. Carbon fiber supports include singled-walled nanotubes, multiwalled nanotubes, or graphitic carbon nanofibers having either platelet, wide herringbone, or narrow tubular herringbone atomic structures. Preparative procedures have been optimized to enhance the performance of these nanocomposites as anode electrocatalysts in direct methanol fuel cells. Pt−Ru nanoparticles are the major metal-containing component of these nanocomposites along with variable amounts of Ru metal. A range of direct methanol fuel cell performance is observed with a Pt−Ru/narrow tubular herringbone graphitic carbon nanofiber nanocomposite showing the highest performance. This performance is equivalent to that recorded for an unsupported Pt−Ru colloid at an anode catalyst loading of 2.7 mg total metal/cm2, but 64% greater than that of the unsupported Pt−Ru colloid at a lower catalyst loading of 1.5 mg/cm2.