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5 "Carbon nanofiber"
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[Korean]
Preparation of CoFe2O4 Nanoparticle Decorated on Electrospun Carbon Nanofiber Composite Electrodes for Supercapacitors
Hyewon Hwang, Seoyeon Yuk, Minsik Jung, Dongju Lee
J Korean Powder Metall Inst. 2021;28(6):470-477.   Published online December 1, 2021
DOI: https://doi.org/10.4150/KPMI.2021.28.6.470
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AbstractAbstract PDF

Energy storage systems should address issues such as power fluctuations and rapid charge-discharge; to meet this requirement, CoFe2O4 (CFO) spinel nanoparticles with a suitable electrical conductivity and various redox states are synthesized and used as electrode materials for supercapacitors. In particular, CFO electrodes combined with carbon nanofibers (CNFs) can provide long-term cycling stability by fabricating binder-free three-dimensional electrodes. In this study, CFO-decorated CNFs are prepared by electrospinning and a low-cost hydrothermal method. The effects of heat treatment, such as the activation of CNFs (ACNFs) and calcination of CFO-decorated CNFs (C-CFO/ACNFs), are investigated. The C-CFO/ACNF electrode exhibits a high specific capacitance of 142.9 F/g at a scan rate of 5 mV/s and superior rate capability of 77.6% capacitance retention at a high scan rate of 500 mV/s. This electrode also achieves the lowest charge transfer resistance of 0.0063 Ω and excellent cycling stability (93.5% retention after 5,000 cycles) because of the improved ion conductivity by pathway formation and structural stability. The results of our work are expected to open a new route for manufacturing hybrid capacitor electrodes containing the C-CFO/ACNF electrode that can be easily prepared with a low-cost and simple process with enhanced electrochemical performance.

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[Korean]
Synthesis of Nitrogen-doped Carbon Nanofibers for Oxygen Reduction Reaction
Geon-Hyoung An, Eun-Hwan Lee, Hyo-Jin Ahn
J Korean Powder Metall Inst. 2016;23(6):420-425.   Published online December 1, 2016
DOI: https://doi.org/10.4150/KPMI.2016.23.6.420
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AbstractAbstract PDF

N-doped carbon nanofibers as catalysts for oxygen-reduction reactions are synthesized using electrospinning and carbonization. Their morphologies, structures, chemical bonding states, and electrochemical performance are characterized. The optimized N-doped carbon nanofibers exhibit graphitization of carbon nanofibers and an increased nitrogen doping as well as a uniform network structure. In particular, the optimized N-doped carbon nanofibers show outstanding catalytic activity for oxygen-reduction reactions, such as a half-wave potential (E1/2) of 0.43 V, kinetic limiting current density of 6.2 mA cm-2, electron reduction pathways (n = 3.1), and excellent long-term stability after 2000 cycles, resulting in a lower E1/2 potential degradation of 13 mV. The improvement in the electrochemical performance results from the synergistic effect of the graphitization of carbon nanofibers and the increased amount of nitrogen doping.

Research Article
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[Korean]
Spindle-shaped Fe2O3 Nanoparticle Coated Carbon Nanofiber Composites for Low-cost Dye-sensitized Solar Cells
Dong-Hyeun Oh, HyeLan An, Bon-Ryul Koo, Hyo-Jin Ahn
J Korean Powder Metall Inst. 2016;23(2):95-101.   Published online April 1, 2016
DOI: https://doi.org/10.4150/KPMI.2016.23.2.95
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  • 1 Citations
AbstractAbstract PDF

Carbon nanofiber (CNF) composites coated with spindle-shaped Fe2O3 nanoparticles (NPs) are fabricated by a combination of an electrospinning method and a hydrothermal method, and their morphological, structural, and chemical properties are measured by field-emission scanning electron microscopy, transmission electron microscopy, Xray diffraction, and X-ray photoelectron spectroscopy. For comparison, CNFs and spindle-shaped Fe2O3 NPs are prepared by either an electrospinning method or a hydrothermal method, respectively. Dye-sensitized solar cells (DSSCs) fabricated with the composites exhibit enhanced open circuit voltage (0.70 V), short-circuit current density (12.82 mA/cm2), fill factor (61.30%), and power conversion efficiency (5.52%) compared to those of the CNFs (0.66 V, 11.61 mA/cm2, 51.96%, and 3.97%) and spindle-shaped Fe2O3 NPs (0.67 V, 11.45 mA/cm2, 50.17%, and 3.86%). This performance improvement can be attributed to a synergistic effect of a superb catalytic reaction of spindle-shaped Fe2O3 NPs and efficient charge transfer relative to the one-dimensional nanostructure of the CNFs. Therefore, spindle-shaped Fe2O3-NPcoated CNF composites may be proposed as a potential alternative material for low-cost counter electrodes in DSSCs.

Citations

Citations to this article as recorded by  
  • Ni Nanoparticles-Graphitic Carbon Nanofiber Composites for Pt-Free Counter Electrode in Dye-Sensitized Solar Cells
    Dong-Hyeun Oh, Bon-Ryul Koo, Yu-Jin Lee, HyeLan An, Hyo-Jin Ahn
    Korean Journal of Materials Research.2016; 26(11): 649.     CrossRef
Articles
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[Korean]
Synthesis of Perforated Polygonal Cobalt Oxides using a Carbon Nanofiber Template
Dong-Yo Sin, Geon-Hyoung An, Hyo-Jin Ahn
J Korean Powder Metall Inst. 2015;22(5):350-355.   Published online October 1, 2015
DOI: https://doi.org/10.4150/KPMI.2015.22.5.350
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  • 2 Citations
AbstractAbstract PDF

Perforated polygonal cobalt oxide (CO3O4) is synthesized using electrospinning and a hydrothermal method followed by the removal of a carbon nanofiber (CNF) template. To investigate their formation mechanism, thermogravimetric analysis, field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Xray photoelectron spectroscopy are examined. To obtain the optimum condition of perforated polygonal CO3O4, we prepare three different weight ratios of the Co precursor and the CNF template: sample A (Co precursor:CNF template- 10:1), sample B (Co precursor:CNF template-3.2:1), and sample C (Co precursor:CNF template-2:1). Among them, sample A exhibits the perforated polygonal CO3O4 with a thin carbon layer (5.7-6.2 nm) owing to the removal of CNF template. However, sample B and sample C synthesized perforated round CO3O4 and destroyed CO3O4 powders, respectively, due to a decreased amount of Co precursor. The increased amount of the CNF template prevents the formation of polygonal CO3O4. For sample A, the optimized weight ratio of the Co precursor and CNF template may be related to the successful formation of perforated polygonal CO3O4. Thus, perforated polygonal CO3O4 can be applied to electrode materials of energy storage devices such as lithium ion batteries, supercapacitors, and fuel cells.

Citations

Citations to this article as recorded by  
  • Synthesis of Nitrogen Doped Protein Based Carbon as Pt Catalysts Supports for Oxygen Reduction Reaction
    Young-geun Lee, Geon-hyeong An, Hyo-Jin Ahn
    Korean Journal of Materials Research.2018; 28(3): 182.     CrossRef
  • Electrochemical Behavior of Well-dispersed Catalysts on Ruthenium Oxide Nanofiber Supports
    Geon-Hyoung An, Hyo-Jin Ahn
    Journal of Korean Powder Metallurgy Institute.2017; 24(2): 96.     CrossRef
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[Korean]
Fabrication of WS2-W-WC Embedded Carbon Nanofiber Composites for Supercapacitors
Yu-Jin Lee, Hyo-Jin Ahn
J Korean Powder Metall Inst. 2015;22(2):116-121.   Published online April 1, 2015
DOI: https://doi.org/10.4150/KPMI.2015.22.2.116
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AbstractAbstract PDF

WS2-W-WC embedded carbon nanofiber composites were fabricated by using electrospinning method for use in high-performance supercapacitors. In order to obtain optimum electrochemical properties for supercapacitors, WS2 nanoparticles were used as precursors and the amounts of WS2 precursors were controlled to 4 wt% (sample A) and 8 wt% (sample B). The morphological, structural, and chemical properties of all samples were investigated by means of field emission photoelectron spectroscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. These results demonstrated that the embedded phases of samples A and B were changed from WS2 to WS2-W-WC through carbothermal reaction during carbonization process. In particular, sample B presented high specific capacitance (~119.7 F/g at 5 mV/s), good high-rate capacitance (~60.5%), and superb cycleability. The enhanced electrochemical properties of sample B were explained by the synergistic effect of the using 1-D structure supports, increase of specific surface area, and improved conductivity from formation of W and WC phases.

Citations

Citations to this article as recorded by  
  • WS2 Nanoparticles Embedded in Carbon Nanofibers for a Pseudocapacitor
    Ki-Wook Sung, Jung Soo Lee, Tae-Kum Lee, Hyo-Jin Ahn
    Korean Journal of Materials Research.2021; 31(8): 458.     CrossRef

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