• Title/Summary/Keyword: electroactivity

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Indirect Electrochemical Oxidation of Phenol by Ce4+, Controlling Surface Insulation of Au Electrode

  • Pyo, Myoung-Ho;Moon, Il-Shik
    • Bulletin of the Korean Chemical Society
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    • v.26 no.6
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    • pp.899-902
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    • 2005
  • Indirect electrochemical oxidation of phenol by $Ce^{4+}$ was investigated in sulfuric acid solutions. It was found that electrode fouling during oxidation of phenol can be controlled by adjusting the time interval (TI) of double potential steps (DPSs). While the electroactivity was greatly decreased after several DPSs of a relatively long TI, repeated DPSs with a short potential pulse showed substantial amounts of electroactivity after a few hundreds or thousands DPS, suggesting that the formation of an insulating layer can be controlled by adjusting a potential program. Effectiveness of the consecutive application of DPSs for phenol decomposition was confirmed by GC-MS.

Lithium Electroactivity of Cobalt Oxide Nanoparticles Synthesized Using Thermolysis Process (열분해 공정을 통해 합성된 산화 코발트 나노입자의 리튬 전기화학반응성)

  • Jin, Yun-Ho;Shim, Hyun-Woo;Kim, Dong-Wan
    • Journal of the Korean Ceramic Society
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    • v.48 no.6
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    • pp.636-640
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    • 2011
  • Nano-sized cobalt (II) oxide nanoparticles with a high crystallinity were synthesized using thermolysis of a $Co^{2+}$-oleate precursor at 310$^{\circ}C$. The phase and morphology of as-prepared cobalt oxide nanoparticles were characterized using X-ray diffraction, high-resolution transmission electron microscopy, and Brunauer-Emmett-Teller surface area measurements. The cobalt oxide nanoparticles were found to be spherical nanoclusters with an average diameter of approximately 200 nm, consisting of tiny nanocrystals (10-20 nm). Furthermore, the Li electroactivites of the cobalt oxide nanoparticles were investigated using cyclic voltammetry and galvanostatic cycling. The cobalt oxide nanoparticles could deliver high capacities over 420 mA h $g^{-1}$ at a C/5 current rate.

Preparation and Electroactivities of Carbon Nanotubes-supported Metal Catalyst Electrodes Prepared by a Potential Cycling

  • Kim, Seok;Jung, Yong-Ju;Park, Soo-Jin
    • Carbon letters
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    • v.10 no.3
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    • pp.213-216
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    • 2009
  • The electrochemical deposition of Pt nanoparticles on carbon nanotubes (CNTs) supports and their catalytic activities for methanol electro-oxidation were investigated. Pt catalysts of 4~12 nm average crystalline size were grown on supports by potential cycling methods. Electro-plating of 12 min time by potential cycling method was sufficient to obtain small crystalline size 4.5 nm particles, showing a good electrochemical activity. The catalysts' loading contents were enhanced by increasing the deposition time. The crystalline sizes and morphology of the Pt/support catalysts were evaluated using X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). The electrochemical behaviors of the Pt/support catalysts were investigated according to their characteristic current-potential curves in a methanol solution. In the result, the electrochemical activity increased with increased plating time, reaching the maximum at 12 min, and then decreased. The enhanced electroactivity for catalysts was correlated to the crystalline size and dispersion state of the catalysts.

Effect of Graphite Nanofibers Addition on the Electrochemical Behaviors of Platinum Nanoparticles Deposited on Activated Carbons (활성탄소에 담지된 백금나노입자의 전기화학적 거동에 대한 그라파이트 나노섬유 첨가효과)

  • Jo, Wonbin;Oh, Misoon;Kim, Juhyun;Kim, Seok
    • Korean Chemical Engineering Research
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    • v.48 no.6
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    • pp.673-678
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    • 2010
  • In the present study, mixed carbon-supported platinum(Pt) nanoparticles were prepared by a chemical reduction method of Pt precursor solution on two types of carbon materials such as activated carbons(ACs) and graphite nanofibers(GNFs). Average crystalline sizes and loading levels of Pt metal particles could be controlled by changing a content of GNFs. The highest electroactivity for methanol oxidation was obtained by preparing the carbon supports having 15 wt% GNFs. Furthermore, with an increase of GNFs content from 0% to 15%, an electrical conductivity was changed from $10^{-4}S/cm$ to $10^{-1}S/cm$. By an introduction of 10 wt% GNFs additive, the electroactivity of platinum particles was enhanced, but was saturated in the case of 15 wt% GNFs contents. This was related with the fact that the electroactivity change was dependent on the electrical conductivity of mixed carbon supports and Pt particle deposition content or deposition morphology.

Synthesis and Li Electroactivity of MnS/Carbon Nanotube Composites (MnS / 카본나노튜브 복합체의 합성과 리튬 전기화학적 거동)

  • Lee, Gwang-Hee;Min, Kyung-Mi;Kim, Dong-Wan
    • Journal of the Korean Ceramic Society
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    • v.50 no.6
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    • pp.539-544
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    • 2013
  • A simple synthetic process is demonstrated for the preparation of MnS/carbon nanotube (CNT) composites for Li ion battery electrodes. CNTs were initially treated using a strong acid solution to generate carboxylate ions ($-COO^-$) on their surfaces. The MnS/CNT composites were synthesized by a polyvinyl-pyrrolidone-assisted hydrothermal method in the presence of as-functionalized CNTs. The phase and morphology of the MnS/CNT composites and pure MnS microspheres were characterized using X-ray diffraction and high-resolution transmission electron microscopy. Furthermore, the Li electroactivity levels of the MnS/CNT composites and MnS microspheres were investigated using cyclic voltammetry and galvanostatic cycling. The MnS/CNT composite electrodes showed higher specific capacities exceeding 365 $mA\;h\;g^{-1}$ at a C/10 current rate and enhanced cyclic performance compared to pure MnS microspheres.

Synthesis of Electroactive Polythiophene Derivatives and Its Application for Biointerface (I) (전기적 활성을 갖는 폴리티오펜 유도체들의 합성과 생체계면에의 응용 (I))

  • 정선형;배진영;김지흥;정동준
    • Polymer(Korea)
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    • v.26 no.1
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    • pp.28-36
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    • 2002
  • In this study, we synthesized novel thiophene derivatives by the protection of the carboxyl group of 3-thiophene acetic acid with differently substituted benzyl groups. While 3-thiophene acetic acid is not electro-polymerizable, the modified monomers can be easily electro-oxidized to form stable electroactive polymers. The protecting groups can be easily removed in the solid state and the desired reactive carboxyl group can be introduced on the polymer surface. SEM observations show that obtained polymer films show a very good film surface and homogeneous morphology on the Pt electrode. After introduction of macromonomer, FT-IR spectrum shows new absorption bands at 1650 and $1550 cm^{-1}$, which is consistent with the formation of an amide bond. Electroactivity measurements were examined by cyclic voltammogram(CV). These polymers showed the characteristic electrochemical behavior of poly(3-alkylthiophene)s with reversible redox transition in the range of 0.7-0.9 V.

Study on urea precursor effect on the electroactivities of nitrogen-doped graphene nanosheets electrodes for lithium cells

  • Kim, Ki-Yong;Jung, Yongju;Kim, Seok
    • Carbon letters
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    • v.19
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    • pp.40-46
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    • 2016
  • Nitrogen-atom doped graphene oxide was considered to prevent the dissolution of polysulfide and to guarantee the enhanced redox reaction of sulfur for good cycle performance of lithium sulfur cells. In this study, we used urea as a nitrogen source due to its low cost and easy preparation. To find the optimum urea content, we tested three different ratios of urea to graphene oxide. The morphology of the composites was examined by field emission scanning electron microscope. Functional groups and bonding characterization were measured by X-ray photoelectron spectroscopy. Electrochemical properties were characterized by cyclic voltammetry in an organic electrolyte solution. Compared with thermally reduced graphene/sulfur (S) composite, nitrogen-doped graphene/S composites showed higher electroactivity and more stable capacity retention.

Synthesis and Characterization of Conductive Polyaniline-Modified Polymers via Nitroxide Mediated Radical Polymerization (NMRP 중합법을 이용한 전도성 폴리아닐린-수식 고분자의 제조와 특성)

  • Jaymand, Mehdi
    • Polymer(Korea)
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    • v.34 no.6
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    • pp.553-559
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    • 2010
  • The paper describes the preparation and characterization of conductive polyaniline-modified polymers by growing of aniline onto functionalized poly(styrene-co-p-methylstyrene) [P(St-co-MSt)]. For this purpose, P(St-co-MSt) was synthesized via nitroxide mediated radical polymerization (NMRP) and then N-boromosuccinimide was used for introduction of bromine to the benzylic positions of copolymer. Afterwards, 1,4-phenylenediamine was linked to the brominated P(St-co-MSt) and functionalized copolymer $[P(St-co-MSt)-NH_2]$ was prepared. The graft copolymerization of aniline monomers onto functionalized P(St-co-MSt) was initiated by oxidized phenylamine groups after addition of ammonium peroxydisulfate (APS), and p-toluenesulfonic acid-doped PANI was chemically grafted onto P(St-co-MSt) via oxidation polymerization. The obtained terpolymer was studied by FTIR and UV-Vis spectroscopy and its thermal behaviour were examined by DSC and TGA analyses. The conductivity of terpolymer was measured by four-point probe method and electroactivity was measured by cyclic voltammetry (CV). The solubility of P(St-co-MSt)-g-PANI was examined in common organic solvents.

The Preparation of Poly(N-methylpyrrole) Bilayers with Entrapped Anthraquinone-2-sulfonate

  • 표명호;김현수
    • Bulletin of the Korean Chemical Society
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    • v.18 no.11
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    • pp.1195-1199
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    • 1997
  • Anthraquinone-2-sulfonate (AQS) release from poly(N-methylpyrrole anthraquinone-2-sulfonate) (PNMP-AQS) was investigated at open circuit and compared with electrochemically stimulated release during potential cycling. It was found that the fast AQS release from PNMP-AQS single layers is substantially retarded and the amounts of spontaneously and electrochemically releasable AQS can be reduced by constructing bilayers, consisting of PNMP-AQS inner layers and PNMP outer layers. PNMP-Cl outer layers exhibited higher effectiveness for entrapping AQS within inner layers than PNMP/poly(styrene slfonate). The effects of outer layer thicknesses on AQS release were also examined with PNMP-AQS:PMP-Cl. The electroactivity enhancement of PNMP-AQS:PNMP-Cl bilayers due to entrapped AQS was confirmed by chronocoulometry.

Methanol oxidation behaviors of PtRu nanoparticles deposited onto binary carbon supports for direct methanol fuel cells

  • Park, Soo-Jin;Park, Jeong-Min;Lee, Seul-Yi
    • Carbon letters
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    • v.14 no.2
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    • pp.121-125
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    • 2013
  • In this study, PtRu nanoparticles deposited on binary carbon supports were developed for use in direct methanol fuel cells using carbon blacks (CBs) and multi-walled carbon nanotubes (MWCNTs). The particle sizes and morphological structures of the catalysts were analyzed using X-ray diffraction and transmission electron microscopy, and the PtRu loading content was determined using an inductively coupled plasma-mass spectrometer. The electrocatalytic characteristics for methanol oxidation were evaluated by means of cyclic voltammetry with 1 M $CH_3OH$ in a 0.5 M $H_2SO_4$ solution as the electrolyte. The PtRu particle sizes and the loading level were found to be dependent on the mixing ratio of the two carbon materials. The electroactivity of the catalysts increased with an increasing MWCNT content, reaching a maximum at 30% MWCNTs, and subsequently decreased. This was attributed to the introduction of MWCNTs as a secondary support, which provided a highly accessible surface area and caused morphological changes in the carbon supports. Consequently, the PtRu nanoparticles deposited on the binary support exhibited better performance than those deposited on the single support, and the best performance was obtained when the mass ratio of CBs to MWCNTs was 70:30.