• Title/Summary/Keyword: metal catalyst

Search Result 119, Processing Time 0.102 seconds

Characteristic of Ni and Co metal-catalyst surface roughness in graphene (Ni와 Co 촉매금속의 표면 거칠기에 따른 그래핀 성장 특성)

  • Kim, Eun-Ho;An, Hyo-Sub;Jang, Hyon-Chul;Cho, Won-Ju;Lee, Wan-Kyu;Jung, Jong-Wan
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • /
    • pp.263-263
    • /
    • 2010
  • High temperature annealing is required to synthesize graphene using CVD. When thin metal catalyst is used for the synthesis, the high temperature pre-annealing makes the thin catalyst highly agglomerated. We investigated the agglomeration effect on the shape of the synthesized graphene. It is found that high temperature annealing makes randomly distributed many hole or blister on metal catalyst, and the synthesized graphene features floral pattern around the hole. The floral patterns of graphene turned out to be multi-layers and higher D peaks in raman spectrum.

  • PDF

Dependence of Molecular Recognition for a Specific Cation on the Change of the Oxidation State of the Metal Catalyst Component in the Hydrogel Network

  • Basavaraja, Chitragara;Park, Do-Young;Choe, Young-Min;Park, Hyun-Tae;Zhao, Yan Shuang;Yamaguchi, Tomohiko;Huh, Do-Sung
    • Bulletin of the Korean Chemical Society
    • /
    • v.28 no.5
    • /
    • pp.805-810
    • /
    • 2007
  • Molecular recognition for a specific cation depending on the change of the oxidation state of the metal catalyst component contained in the hydrogel network has been studied in a self-oscillating hydrogel. The selfoscillating hydrogels are synthesized by the copolymerization of N-isopropylacrylamide (NIPAAm), lead methacrylic acid (Pb(MAA)2), and Ru(bpy)3 2+ monomer as a metal catalyst component. The recognition for a specific cation (in this study, Ca2+ has been used) is characterized by the adsorbed amount of Ca2+ into the gel. The recognition of the gels for Ca2+ is higher at the temperature below the LCST, and also higher at the oxidized state than at reduced state of the metal catalyst component which corresponds to a more swollen state. Moreover, a propagating wave induced by a periodic change of the oxidation state with the diffusion phenomena in the oscillating hydrogel shows a possibility for temporal and site-specific molecular recognition due to the local swelling of the gel.

Recent Research Progress on the Atomic Layer Deposition of Noble Metal Catalysts for Polymer Electrolyte Membrane Fuel Cell (고분자 전해질 연료전지용 촉매 소재 개발을 위한 원자층증착법 연구 동향)

  • Han, Jeong Hwan
    • Journal of Korean Powder Metallurgy Institute
    • /
    • v.27 no.1
    • /
    • pp.63-71
    • /
    • 2020
  • It is necessary to fabricate uniformly dispersed nanoscale catalyst materials with high activity and long-term stability for polymer electrolyte membrane fuel cells with excellent electrochemical characteristics of the oxygen reduction reaction and hydrogen oxidation reaction. Platinum is known as the best noble metal catalyst for polymer electrolyte membrane fuel cells because of its excellent catalytic activity. However, given that Pt is expensive, considerable efforts have been made to reduce the amount of Pt loading for both anode and cathode catalysts. Meanwhile, the atomic layer deposition (ALD) method shows excellent uniformity and precise particle size controllability over the three-dimensional structure. The research progress on noble metal ALD, such as Pt, Ru, Pd, and various metal alloys, is presented in this review. ALD technology enables the development of polymer electrolyte membrane fuel cells with excellent reactivity and durability.

Etching Treatment of Vertically Aligned Carbon Nanotubes for the Application to Biosensor (바이오센서로의 응용을 위한 수직 배열된 탄소나노튜브의 식각처리)

  • Choi, Eun-Chang;Park, Yong-Seob;Choi, Won-Seok;Hong, Byung-You
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
    • /
    • v.21 no.7
    • /
    • pp.594-598
    • /
    • 2008
  • The metal catalyst particles which there is as impurities on a tip part of carbon nanotube (CNT) are not good to apply it to a nano-electronic device. It was very important the opening of CNT-tip to fix a target bio material and a material to accept in CNT in a biosensor, so we performed $HNO_3$ wet etching to remove the metal catalyst particle which there was on a tip part of CNT grown up in the study and observed the opened CNT-tip with etching time. We synthesized the CNTs using a HF-PECVD method and choses the CNT length of 700 nm for the application of nano-electronic device such as a biosensor etc.. We observed the opened CNT-tip with wet etching times of $HNO_3$ (10, 30, 60 min). From the results, we observed that the CNT-tip was opened with the increase of wet etching time lively. In case of CNTs etched during 60 min, we confirmed that there was not the ratio of Ni included in CNTsI as catalyst. Conclusively, in the case of CNT etched for 60 minutes, it is completely good for application of a biosensor and, in addition, the metal-free CNTs will contribute to the application of other nanoelectronic devices.

Growth of SiO2 Nanowire by Catalyst Evaporation Method (촉매의 휘발법에 의한 이산화규소 나노와이어의 성장)

  • Rho, Dae-Ho;Kim, Jae-Soo;Byun, Dong-Jin;Lee, Jae-Hoon;Yang, Jae-Woong;Kim, Na-Ri
    • Korean Journal of Materials Research
    • /
    • v.15 no.3
    • /
    • pp.189-194
    • /
    • 2005
  • [ $SiO_2$ ] nanowires were synthesized using the catalyst evaporation method. Grown nanowires had different shapes by kind of used metal catalyst. Mean diameters of grown $SiO_2$ nanowire were about 30 nm. The kind of catalysts affected microstructure of grown $SiO_2$ nanowire because of its typical growth reactions through the liquid state metal catalysts. Optical property were measured by photoluminescence spectroscopy. Relatively broad peak was obtained and mean peak positioned at 450 nm.

Density Functional Study on the C-H Bond Cleavage of Aldimine by a Rhodium(I) Catalyst

  • Yoo, Kyung-Hwa;Jun, Chul-Ho;Choi, Cheol-Ho;Sim, Eun-Ji
    • Bulletin of the Korean Chemical Society
    • /
    • v.29 no.10
    • /
    • pp.1920-1926
    • /
    • 2008
  • We investigated the C-H bond activation mechanism of aldimine by the [RhCl$(PPH_3)_3$] model catalyst using DFT B3LYP//SBKJC/6-31G*/6-31G on GAMESS. Due to their potential utility in organic synthesis, C-H bond activation is one of the most active research fields in organic and organometallic chemistry. C-H bond activation by a transition metal catalyst can be classified into two types of mechanisms: direct C-H bond cleavage by the metal catalyst or a multi-step mechanism via a tetrahedral transition state. There are three structural isomers of [RhCl$(PH_3)_2$] coordinated aldimine that differ in the position of chloride with respect to the molecular plane. By comparing activation energies of the overall reaction pathways that the three isomeric structures follow in each mechanism, we found that the C-H bond activation of aldimine by the [RhCl$(PH_3)_3$] catalyst occurs through the tetrahedral intermediate.