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- Xie, Kunpeng, 1985, et al.
(författare)
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A reevaluation of the correlation between the synthesis parameters and structure and properties of nitrogen-doped carbon nanotubes
- 2015
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Ingår i: Journal of Energy Chemistry. - : Elsevier BV. - 2095-4956. ; 24:4, s. 407-415
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen-doped carbon nanotubes (NCNTs) were synthesized by chemical vapor deposition using cobalt-based oxides as catalyst and ethylenediamine (EDA) as carbon/nitrogen precursor. The influence of growth time, EDA concentration and growth temperature on the morphology, yield, composition, graphitization and oxidation resistance of the NCNTs was systematically investigated by using Raman spectroscopy, temperature-programmed oxidation and other techniques. The NCNT growth from ethylenediamine with a high N/C ratio involves several processes including mainly (1) catalytic growth of NCNTs, (2) homogeneous gas-phase decomposition of EDA, (3) non-catalytic deposition of pyrolytic carbon/nitrogen species and (4) surface etching of amorphous carbon or carbon at defect sites through gasification. At a later growth stage the etching process appears to be dominating, leading to the thinning of nanotubes and the decrease of yield. Moreover, the surface etching through carbon gasification strongly influences the structure and degree of graphitization of NCNTs.
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| 3. |
- Xie, Kunpeng, 1985, et al.
(författare)
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Co3O4–MnO2–CNT Hybrids Synthesized by HNO3 Vapor Oxidation of Catalytically Grown CNTs as OER Electrocatalysts
- 2015
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Ingår i: ChemCatChem. - : Wiley. - 1867-3899 .- 1867-3880. ; 7:18, s. 3027-3035
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Tidskriftsartikel (refereegranskat)abstract
- An efficient two-step gas-phase method was developed for the synthesis of Co3O4–MnO2–CNT hybrids used as electrocatalysts in the oxygen evolution reaction (OER). Spinel Co–Mn oxide was used for the catalytic growth of multiwalled carbon nanotubes (CNTs) and the amount of metal species remaining in the CNTs was adjusted by varying the growth time. Gas-phase treatment in HNO3 vapor at 200 °C was performed to 1) open the CNTs, 2) oxidize encapsulated Co nanoparticles to Co3O4 as well as MnO nanoparticles to MnO2, and 3) to create oxygen functional groups on carbon. The hybrid demonstrated excellent OER activity and stability up to 37.5 h under alkaline conditions, with longer exposure to HNO3 vapor up to 72 h beneficial for improved electrocatalytic properties. The excellent OER performance can be assigned to the high oxidation states of the oxide nanoparticles, the strong electrical coupling between these oxides and the CNTs as well as favorable surface properties rendering the hybrids a promising alternative to noble metal based OER catalysts.
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| 4. |
- Xie, Kunpeng, 1985, et al.
(författare)
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Promoting effect of nitrogen doping on carbon nanotube-supported RuO2 applied in the electrocatalytic oxygen evolution reaction
- 2016
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Ingår i: Journal of Energy Chemistry. - : Elsevier BV. - 2095-4956. ; 25:2, s. 282-288
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Tidskriftsartikel (refereegranskat)abstract
- RuO2 nanoparticles supported on multi-walled carbon nanotubes (CNTs) functionalized with oxygen (OCNTs) and nitrogen (NCNTs) were employed for the oxygen evolution reaction (OER) in 0.1 M KOH. The catalysts were synthesized by metal-organic chemical vapor deposition using ruthenium carbonyl (Ru3(CO)12) as Ru precursor. The obtained RuO2/OCNT and RuO2/NCNT composites were characterized using TEM, H2-TPR, XRD and XPS in order probe structure-activity correlations, particularly, the effect of the different surface functional groups on the electrochemical OER performance. The electrocatalytic activity and stability of the catalysts with mean RuO2 particle sizes of 13-14 nm was evaluated by linear sweep voltammetry, cyclic voltammetry, and chronopotentiometry, showing that the generation of nitrogen-containing functional groups on CNTs was beneficial for both OER activity and stability. In the presence of RuO2, carbon corrosion was found to be significantly less severe.
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