• Title/Summary/Keyword: electrocatalysts

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Fine Structure Effect of PdCo electrocatalyst for Oxygen Reduction Reaction Activity: Based on X-ray Absorption Spectroscopy Studies with Synchrotron Beam

  • Kim, Dae-Suk;Kim, Tae-Jun;Kim, Jun-Hyuk;Zeid, E. F. Abo;Kim, Yong-Tae
    • Journal of Electrochemical Science and Technology
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    • v.1 no.1
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    • pp.31-38
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    • 2010
  • In this study, we have demonstrated the fine structure effect of PdCo electrocatalyst on oxygen reduction reaction activity with different alloy composition and heat-treatment time. In order to identify the intrinsic factors for the electrocatalytic activity, various X-ray analyses were used, including inductively coupled plasma-atomic emission spectrometer, transmission electron microscopy, X-ray diffractometer, and X-ray Absorption Spectroscopy technique. In particular, extended X-ray absorption fine structure was employed to extract the structural parameters required for understanding the atomic distribution and alloying extent, and to identify the corresponding simulated structures by using FEFF8 code and IFEFFIT software. The electrocatalytic activity of PdCo alloy nanoparticles for the oxygen reduction reaction was evaluated by using rotating disk electrode technique and correlated to the change in structural parameters. We have found that Pd-rich surface was formed on the Co core with increasing heating time over 5 hours. Such core shell structure of PdCo/C showed that a superior oxygen reduction reaction activity than pure Pd/C or alloy phase of PdCo/C electrocatalysts, because the adsorption energy of adsorbates was apparently reduced by lowering the dband center of the Pd skin due to a combination of the compressive strain effect and ligand effect.

Biomimetic Copper Complex Containing Polymer Modified Electrode for Electrocatalytic Reduction of Oxygen

  • Saravanakumar, D.;Nagarale, Rajaram Krishna;Jirimali, Harish Chandra;Lee, Jong Myung;Song, Jieun;Lee, Junghyun;Shin, Woonsup
    • Journal of Electrochemical Science and Technology
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    • v.7 no.4
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    • pp.298-305
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    • 2016
  • The development of non-precious metal based electrocatalysts is highly desired for the oxygen reduction reaction (ORR) as alternates to noble metal based ORR electrocatalysts. Herein, we report mononulcear copper(II) complex $[CuLbpy]ClO_4$ (L=4-[(2-hydroxyphenylimino)methyl]benzoic acid) containing poly(allylamine.HCl) polymer (PAlACuLbpy) as an electrocatalyst for oxygen reduction reaction (ORR). PAlACuLbpy was mixed with poly(acrylic acid) and tetraethylortho silicate to prepare a composite and then deposited on the screen printed electrode surface. The modified electrode (PAlACuLbpy/PCE) is highly stable and showed a quasi-reversible redox behavior with $E_{1/2}=-0.2V$ vs. Ag/AgCl(3 M KCl) in 0.1 M phosphate buffer at pH 7 under argon atmosphere. PAlACuLbpy/PCE exhibited a remarkable ORR activity with an onset potential of -0.1 V vs Ag/AgCl in 0.1 M PB (pH 7) in the presence of oxygen. The kinetics for ORR was studied by rotating disk voltammetry in neutral aqueous medium and the results indicated that the number of electrons involving in the ORR is four and the conversion products are water and hydrogen peroxide.

Competitiveness of Formic Acid Fuel Cells: In Comparison with Methanol (포름산 연료전지의 경쟁력)

  • Uhm, Sunghyun;Seo, Minhye;Lee, Jaeyoung
    • Applied Chemistry for Engineering
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    • v.27 no.2
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    • pp.123-127
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    • 2016
  • Methanol fuel cells having advantages of relatively favorable reaction kinetics and higher energy density have attracted increasing interests as best alternative to hydrogen fuel cell because of H2 production, storage and distribution issues. While there have been extensive research works on developing key components such as electrocatalysts as well as their physicochemical properties in practical formic acid fuel cells, there have also been urgent requests for investigating which fuel sources will be more suitable for direct liquid fuel cells in future. In this mini-review, we highlight the overall interest and outlook of formic acid fuel cells in terms of electrocatalysts, fuel supply and crossover, water management, fuel cell efficiency and system integration in comparison with methanol fuel cells.

Preparation and Electrochemical Performances Comparison of Carbon and Hydrogel Electrocatalysts for Seawater Battery (해수 전지용 탄소계 촉매와 Hydrogel 촉매의 제조 및 이들의 전기화학적 특성 비교)

  • Kim, Kyoungho;Na, Young Soo;Lee, Man Sung
    • Journal of the Korean Electrochemical Society
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    • v.21 no.4
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    • pp.61-67
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    • 2018
  • As emerging the new electric devices, the commercial lithium ion batteries have faced with various challenges. In this regard, many efforts to solve challenges have been tried. In order to solve the above problems in terms of development of a new secondary battery, we successfully demonstrated the two electrocatalysts, such as MCWB and PPY hydrogel, PPY hydrogel and MCWB showed typical H3-type BET isotherm, indicating that micro- and mesopores existed. Especially, in terms of voltage efficiency at the first cycle, PPY hydrogel was higher than that of MCWB, but lower than that of PtC. More interestingly, the PPY hygrogel based seawater battery exhibited charge-discharge reversibility during 20 cycles, and the voltage efficiencies ranged from 70.32 % to 77.35 % in cyclic performance test.

Electrochemical Oxidation of Ethanol at $RuO_2-Modified$ Nickel Electrode in Alkaline Media Studied by Electrochemical Impedance Spectroscopy

  • Kim Jae-Woo;Park Su-Moon
    • Journal of the Korean Electrochemical Society
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    • v.3 no.2
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    • pp.76-80
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    • 2000
  • Electrochemical oxidation of ethanol has been studied at nickel and $RuO_2-modified$ nickel electrodes in 1 M KOH using electrochemical impedance spectroscopy. Equivalent circuits have been worked out from simulation of impedance data to model oxidation of ethanol as well as the passivation of the electrode. The charge-transfer resistances for oxidation of these electrodes became smaller in the presence of ethanol than in its absence. The nickel substrate facilitated ethanol oxidation at $RuO_2-modified$ nickel electrodes. We also describe the Performance of nanosized electrocatalysts of the same composition in comparison to those of the bulk electrodes. The nanosized electrodes were obtained by electrode-positing the alloy from complexed form of these metal ions with fourth and fifth generation polyamidoamine dendrimers.

The fabrication of electrode and characterization of performance in the PEMFC (고분자 연료전지의 전극 제조 및 성능 평가)

  • Park In-Su;Cho Yonghun;Choi Baeckbeom;Jung Daesik;Cho Yoonhwan;Sung Yung-Eun
    • 한국신재생에너지학회:학술대회논문집
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    • 2005.06a
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    • pp.227-230
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    • 2005
  • There is a worldwide interest In the development and commercialization of PEMFCs for vehicular and stationary applications. The major problem in the practical use of PEMFCs is the deactivation of the Pt anode electrocatalyst by the adsorption of carbon monoxide. Therefore, intensive work has been devoted to finding electrocatalysts that are tolerant to CO in hydrogen at operating temperatures bellow $100^{\circ}C$. Also, DMFC is considered to be one of the most promising technologies for energy generation. But, the most important problem associated with the DMFC is the slow reaction rate of methanol oxidation and the second major problem is fuel crossover. So, the performance of a state-of-the-art DMFC is considerably lower than that of hydrogen-fuelled PEMFC. In this research, the preparation and characterization of electrode materials will be introduced. Also, some electrochemical techniques for the characterization of PEMFCs will be presented.

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Water Oxidation Mechanism for 3d Transition Metal Oxide Catalysts under Neutral Condition

  • Seo, Hongmin;Cho, Kang Hee;Ha, Heonjin;Park, Sunghak;Hong, Jung Sug;Jin, Kyoungsuk;Nam, Ki Tae
    • Journal of the Korean Ceramic Society
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    • v.54 no.1
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    • pp.1-8
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    • 2017
  • Electrochemical water splitting to produce hydrogen energy is regarded as a promising energy conversion process for its environmentally friendly nature. To improve cell efficiency, the development of efficient water oxidation catalysts is essentially demanded. For several decades, 3d transition metal oxides have been intensively investigated for their high activity, good durability and low-cost. This review covers i) recent progress on 3d transition metal oxide electrocatalysts and ii) the reaction mechanism of oxygen evolving catalysis, specifically focused on the proposed pathways for the O-O bond formation step.

Solar-hydrogen Production by a Monolithic Photovoltaic-electrolytic Cell

  • Jeon, Hyo Sang;Min, Byoung Koun
    • Journal of Electrochemical Science and Technology
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    • v.3 no.4
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    • pp.149-153
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    • 2012
  • Among the various solar-hydrogen production techniques a combination of a photovoltaic (PV) and an electrolytic cell into one single system, a monolithic PV-electrolytic cell, has been suggested as a promising one in terms of efficiency and stability. In this mini-review, we describe our recent efforts on the fabrication of the monolithic PV-electrolytic cell. Particularly, we focus on the electrocatalysts for water oxidation and its fabrication method suitable for a monolithic PV-electrolytic cell. We also introduce proto-type devices with a dye-sensitized solar cell module and an InGaP/GaAs photoelectrodes.

Irreversibly Adsorbed Tri-metallic PtBiPd/C Electrocatalyst for the Efficient Formic Acid Oxidation Reaction

  • Sui, Lijun;An, Wei;Rhee, Choong Kyun;Hur, Seung Hyun
    • Journal of Electrochemical Science and Technology
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    • v.11 no.1
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    • pp.84-91
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    • 2020
  • The PtBi/C and PtBiPd/C electrocatalysts were synthesized via the irreversible adsorption of Pd and Bi ions precursors on commercial Pt/C catalysts. XRD and XPS revealed the formation of an alloy structure among Pt, Bi, and Pd atoms. The current of direct formic acid oxidation (Id) increased ~ 8 and 16 times for the PtBi/C and PtBiPd/C catalysts, respectively, than that of commercial Pt/C because of the electronic, geometric, and third body effects. In addition, the increased ratio between the current of direct formic acid oxidation (Id) and the current of indirect formic acid oxidation (Iind) for the PtBi/C and PtBiPd/C catalysts suggest that the dehydrogenation pathway is dominant with less CO formation on these catalysts.

Electro-catalytic Performance of PtRu Catalysts Supported on Urea-treated MWNTs for Methanol Oxidation

  • Park, Jeong-Min;Park, Soo-Jin
    • 한국신재생에너지학회:학술대회논문집
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    • 2009.11a
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    • pp.159-159
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    • 2009
  • In this work, nitrogen and oxygen functionalities was introduced to the graphite nanofibers (GNFs) and their effect on electrocatalytic performance of the GNF supports for direct methanol fuel cells (DMFCs) was invesigated. The nitrogen and oxygen groups were introduced through the urea treatments and acid treatment, respectively. And, PtRu catalysts deposited on modified GNFs were prepared by a chemical reduction method. The catalysts were characterized by means of elemental analysis, nitrogen adsorption, and X-ray photoelectron spetroscopy (XPS). The structure and morphological characteristics of the catalysts were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). As a result, the Pt-Ru nanoparticles were impregnated on GNFs with good formation in 3-5 nm. And, the cyclic voltammograms for methanol oxidation revealed that the methanol oxidation peak varied depending on changes of surface functional groups. It was thus considered that the PtRu deposition was related to the reduction of PtRu and surface characteristics of the carbon supports. The changes of surface functional groups were related to PtRu reduction, significantly affect the methanol oxidation activity of anode electrocatalysts in DMFCs.

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