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Abstract: The fabrication of carbon nanocapsules and carbon nanotubes (CNTs) using an acetylene flame method was investigated. Carbon nanocapsules, a graphitic structure of nanoparticles with a hollow core, were synthesized using catalyst-free acetylene flames while CNTs were formed with the presence of cobalt-based catalysts in addition to acetylene flames. When the synthesis of these materials was carried out, the results showed that a massive amount of high-purity carbon nanocapsules with a particle size in the range of 15–30nm can be produced with the acetylene flame method. The CNTs produced were multi-walled carbon nanotubes measuring a few micrometers in length and 20–30nm in diameter. The acetylene flame method holds great potential for the cost-effective production of CNTs as well as carbon nanocapsules. [Copyright &y& Elsevier]

Abstract: Platelet graphite nanofibers (PGNFs) were synthesized by thermal decomposition from a mixture containing polymer and catalyst. The hydrogen storage capacity of the material was measured using the volumetric method carried out at 298K at a pressure up to 4.83MPa. The results show that the PGNF possess a 3.3wt.% hydrogen storage capacity. The gaseous molecules were adsorbed between two graphene planes in the PGNFs and residual amounts of hydrogen were possession within PGNFs while pressure decreased to ambient conditions. X-ray diffraction was used to understand the PGNF structural modifications before and after hydrogen uptake. We found that the PGNF interlayer undergoes expansion and returns back to the initial value before and after hydrogen uptake. [Copyright &y& Elsevier]

[Display omitted] • The novel CNT-CoFe/NC and CNT-CoS 2 Fe/NC was fabricated by thermal treatments and vulcanization. • CNT-CoFe/NC shows a better ORR performance than Pt/C while CNT-CoS 2 Fe/NC shows a better OER performance than RuO 2. • The hybrid catalysts, CNT-CoFe/NC + CNT-CoS 2 Fe/NC, demonstrate a superior performance of rechargeable Zn-air battery. Catalysts with embedded and functionalized elements used for the effective control of oxygen-reduction (ORRs) and oxygen-evolution reactions (OERs) are the key to developing high-performance rechargeable Zn–air batteries (ZABs). Here, carbon nanotube-grafted, Co–Fe embedded, nitrogen-doped porous carbon nano-frameworks (CNT–Co–Fe/NC) were synthesized through the carbonization of Fe-doped zeolitic imidazolate frameworks and vulcanization of the CNT–Co–Fe/NC to form CNT–CoS 2 –Fe/NC. The CNT–CoS 2 –Fe/NC exhibited a superior OER performance with an overpotential of only 1.637 mV at a current density of 10 mA/cm2 and a Tafel slope of 197 mV/dec (which, for RuO 2 , is 112 mV/dec), whereas the CNT–Co–Fe/NC showed an excellent ORR performance with a Tafel slope of 71 mV/dec (which, for 20 wt% Pt/C, is 91 mV/dec). A ZAB was developed with a hybrid catalyst of 50 wt% CNT–Co–Fe/NC and 50 wt% CNT–CoS 2 –Fe/NC in the cathode, and it achieved an excellent specific discharge capacity of 814 mAh/g at 50 mA/cm2, high power density of 245 mW/cm2, and outstanding cycle stability of over 1800 cycles (300 h) at 10 mA/cm2 with a very high retention of 95% and small potential gap of 0.68 V, compared to the corresponding values of 803.7 mAh/g, 215.3 mW/cm2, 900 cycles: retention 92%, and potential gap 0.837 V for 150 h for the ZAB with a hybrid catalyst of Pt/C + RuO 2. It is hypothesized that the ZAB with the novel hybrid catalyst exhibits its excellent catalytic activity and durability as a result of the synergistic effect of the catalyst's embedded heteroatoms and nitrogen–metal/carbon framework that enhances the ORR/OER performance, porous carbon nano-framework that enables rapid diffusion and electrical conduction, and carbon nanotubes that complete the external electrical connection between the catalysts. [ABSTRACT FROM AUTHOR]

Abstract: The combination of porous carbon nanofiber (PCNF) and room-temperature ionic liquid (RTIL) provided a suitable microenvironment for heme-proteins to transfer electron directly. Hemoglobin, myoglobin, and cytochrome c incorporated in PCNF/RTIL films exhibited a pair of well-defined, quasi-reversible cyclic voltammetric peaks at about −0.28V vs. SCE in pH 7.0 buffers, respectively, characteristic of the protein heme Fe(III)/Fe(II) redox couples. The cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the modified electrode. The heme/PCNF/RTIL/CHIT films were also characterized by UV–vis spectroscopy, indicating that heme-proteins in the composite film could retain its native structure. Oxygen, hydrogen peroxide, and nitrite were catalytically reduced at the heme/PCNF/RTIL/CHIT film modified electrodes, showing the potential applicability of the films as the new type of biosensors or bioreactors based on direct electrochemistry of the redox proteins. [Copyright &y& Elsevier]

Abstract: Multiwalled carbon nanotubes (MWNTs) were synthesized using a chemical vapor deposition floating feed method in a vertical reactor. Effects of the preparation variables on the average diameter of carbon nanotubes were systematically examined using the fractional factorial design (FFD), path of the steepest ascent, and central composite design (CCD) coupled with the response surface methodology. From the FFD study, the main and interactive effects of reaction temperature, methane flow rate, and chamber pressure were concluded to be the key factors influencing the diameter of MWNTs. Two empirical models, representing the dependence of the diameter of carbon nanotubes at the vicinities around maximum (420nm) and minimum (15nm) on the reaction temperature and methane flow rate, were constructed in two independent CCD studies. These models, shown as contour diagrams, indicated that the diameter of carbon nanotubes generally increased with increasing reaction temperature and methane flow rate. Based on both models, the diameter of MWNTs from 15 to 420nm can be controlled precisely by using a continuous CVD fabrication method. [Copyright &y& Elsevier]

The aim of this study is to investigate the possibility of using a polymer material, polyvinyl alcohol (PVA), as an additional carbon source to fabricate carbon nanotubes using arc-discharge method. Experiments were carried out using a graphite anode filled with a mixture of PVA and iron group catalysts. The results indicated that PVA material not only can be used for the formation of carbon nanotubes but also for the formation of some novel carbonaceous structures such as spherical nanoparticles, beaded and sheet-like carbon nanostructures. Furthermore, we found that the catalyst content in the PVA filling mixture should be lower than 50 wt%. In addition, novel catalyst precursors, such as Fe2(SO4)3 · nH2O or Fe(NO3)3 · 9H2O, were employed to grow carbon nanotubes. The results showed that these catalyst precursors can be used to form carbon nanotubes if their filling content does not exceed 50 wt%. [Copyright &y& Elsevier]

• GQDs by ball-milling technique with a mixture of carbon nanocapsules and Na 2 CO 3. • The size of GQDs in the range of 1.04.0 nm. • The λ ex is in the range of 280–360 nm, the PL emission peaks are broad with the maximum intensity at the wavelength of 440 nm. Graphene quantum dots (GQDs) have a wide range of applications in energy, optoelectronics, and bio-nanotechnology. However, their high cost is a barrier for commercial application. Here, we report a cost-effective ball-milling method for producing GQDs using a mixture of carbon nanocapsules (20 nm) as the carbon source and sodium carbonate as the intercalation agent. The results show that the proposed exfoliation method produces GQDs with diameters of 1.0–4.0 nm and a very small amount of grafted functional groups that exhibit blue light emission under ultraviolet irradiation. The quantum yield is about 5%. The proposed method has great potential for the production of GQDs using low-cost raw materials. [ABSTRACT FROM AUTHOR]

In this study, carbon-nanotube (CNT)-grafted and nano Co 3 O 4 -doped porous carbon was prepared by the carbonization of a synthesized zeolitic imidazolate framework compound (ZIF-67/ZIF-8) followed by an oxidation treatment. The novel catalyst demonstrated excellent ORR and OER because of the Co 3 O 4 nanoparticles and nitrogen-doped in the carbon framework (NC). In addition, the carbon nanotube grafted on the framework provided a good electrical conductivity while the carbon framework matrix provided a porous skeleton which is beneficial for the mass transfer of electrolyte. In the ORR study, the novel catalyst, CNT-Co 3 O 4 /NC, showed a half-wave potential of −0.124 V at 0.1 M KOH (Pt/carbon: −0.152 V) while the limited current density is 4.84 mA/cm2 (Pt/carbon: 4.9 mA/cm2). In terms of OER performance, the potential is 0.819 V at current density of 10 mA/cm2 (Ir/carbon: 0.771 V). The CNT-Co 3 O 4 /NC catalyst shows a specific capacitance of 814 mAh/g (1.19 V at 50 mA/cm2), which is very close to the theoretical capacitance (820 mAh/g) and the maximum power density was 267 mW/cm2 (0.746 V at 385 mA/cm2) while 255 mW/cm2 (0.711 V at 360 mA/cm2) was obtained using Pt/carbon catalyst. We believe that the novel CNT-Co 3 O 4 /NC can be used as an excellent catalyst in the zinc-air battery. Image 1 • A 3D-network of Co 3 O 4 , NC and CNT show efficient activity in ORR/OER. • The CNT-Co 3 O 4 /NC is as a promising catalyst with specific capacitance of 814 mAh/g. • The ZABs revealed a high peak power density of 267 mW cm2 (0.746 V at 385 mA/cm2). • A better cycling performance of the ZAB using CNT-Co 3 O 4 /NC catalyst than Pt/Carbon. [ABSTRACT FROM AUTHOR]