• Title, Summary, Keyword: Catalyst

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Practical Challenges Associated with Catalyst Development for the Commercialization of Li-air Batteries

  • Park, Myounggu;Kim, Ka Young;Seo, Hyeryun;Cheon, Young Eun;Koh, Jae Hyun;Sun, Heeyoung;Kim, Tae Jin
    • Journal of Electrochemical Science and Technology
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    • v.5 no.1
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    • pp.1-18
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    • 2014
  • Li-air cell is an exotic type of energy storage and conversion device considered to be half battery and half fuel cell. Its successful commercialization highly depends on the timely development of key components. Among these key components, the catalyst (i.e., the core portion of the air electrode) is of critical importance and of the upmost priority. Indeed, it is expected that these catalysts will have a direct and dramatic impact on the Li-air cell's performance by reducing overpotentials, as well as by enhancing the overall capacity and cycle life of Li-air cells. Unfortunately, the technological advancement related to catalysts is sluggish at present. Based on the insights gained from this review, this sluggishness is due to challenges in both the commercialization of the catalyst, and the fundamental studies pertaining to its development. Challenges in the commercialization of the catalyst can be summarized as 1) the identification of superior materials for Li-air cell catalysts, 2) the development of fundamental, material-based assessments for potential catalyst materials, 3) the achievement of a reduction in both cost and time concerning the design of the Li-air cell catalysts. As for the challenges concerning the fundamental studies of Li-air cell catalysts, they are 1) the development of experimental techniques for determining both the nano and micro structure of catalysts, 2) the attainment of both repeatable and verifiable experimental characteristics of catalyst degradation, 3) the development of the predictive capability pertaining to the performance of the catalyst using fundamental material properties. Therefore, under the current circumstances, it is going to be an extremely daunting task to develop appropriate catalysts for the commercialization of Li-air batteries; at least within the foreseeable future. Regardless, nano materials are expected to play a crucial role in this field.

Experimental Investigation of the Effect of Composition on the Performance and Characteristics of PEM Fuel Cell Catalyst Layers

  • Baik, Jung-Shik;Seong, Dong-Mug;Kim, Tae-Min
    • 한국신재생에너지학회:학술대회논문집
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    • pp.157-160
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    • 2007
  • The catalyst layer of a proton exchange membrane (PEM) fuel cell is a mixture of polymer, carbon, and platinum. The characteristics of the catalyst layer play critical role in determining the performance of the PEM fuel cell. This research investigates the role of catalyst layer composition using a Central Composite Design (CCD) experiment with two factors which are Nafion content and carbon loading while the platinum catalyst surface area is held constant. For each catalyst layer composition, polarization curves are measured to evaluate cell performance at common operating conditions, Electrochemical Impedance Spectroscopy (EIS), and Cyclic Voltammetry (CV) are then applied to investigate the cause of the observed variations in performance. The results show that both Nafion and carbon content significantly affect MEA performance. The ohmic resistance and active catalyst area of the cell do not correlate with catalyst layer composition, and observed variations in the cell resistance and active catalyst area produced changes in performance that were not significant relative to compositions of catalyst layers.

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A Study on the Thermal Aging and SOx Poisoning Characteristics on Alumina Supported Silver Catalyst under Diesel Engine Emission Condition (디젤엔진 배기가스조건하에서의 Pt 및 Ag 담지 알루미나 촉매의 열적 노화 특성과 SOx 피독 특성에 관한 연구)

  • 신병선
    • Journal of Korean Society for Atmospheric Environment
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    • v.16 no.2
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    • pp.199-208
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    • 2000
  • In this study we investigated on the possibility of platinum and silver catalysts as de-NOx catalyst for activity test of supported metal oxide catalysts. the study was performed with the change of amount of metal and support types. The catalyst was prepared the activity of alumina supported silver catalyst produced by dry and wet impregnation method respectively and the resistance of sulfur for optimum supported silver catalyst,. As a result the activity of alumina supported platinum catalyst was showed at low temperature region but the case of silver catalyst activated at high temperature region. So we finally chose alumina supported silver catalyst as de-NOx target catalyst because alumina supported catalyst showed higher activity than alumina supported platinum catalyst.

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A Study on Degradation Characteristic and Flow Behavior in De-NOx Catalyst (탈질촉매 내 열화특성과 유동상태에 관한 연구)

  • Hwang, Seung-Min
    • Journal of Environmental Science International
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    • v.19 no.9
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    • pp.1093-1101
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    • 2010
  • In this study, the indirect correlation of degradation characteristic and flow behavior in the de-NOx catalyst is investigated experimentally. The inner flow behavior in the de-NOx catalyst is varied from turbulent flow to laminar flow and the degradation of the de-NOx catalyst is remarkably affected by the inner flow. The degradation of the catalyst is increased in the upstream region near the inlet because injected turbulent flow enhances the adhesion of ash particle on the catalyst surface. The degradation of the catalyst near the inlet also governs the overall efficiency of the catalyst. The amount of adhered ash particles on the catalyst surface decreases as they progress downstream. This is due to the inner flow transition from turbulent flow to laminar flow.

A Strategy for Homogeneous Current Distribution in Direct Methanol Fuel Cells through Spatial Variation of Catalyst Loading

  • Park, Sang-Min;Kim, Sang-Kyung;Peck, Dong-Hyun;Jung, Doo-Hwan
    • Journal of Electrochemical Science and Technology
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    • v.8 no.4
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    • pp.331-337
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    • 2017
  • A simple strategy is proposed herein for attaining uniform current distribution in direct methanol fuel cells by varying the catalyst loading over the electrode. In order to use the same total catalyst amount for a serpentine flow field, three spatial variation types of catalyst loading were selected: enhancing the cathode catalyst loading (i) near the cathode outlet, (ii) near the cathode inlet, and (iii) near the lateral areas. These variations in catalyst loading are shown to improve the homogeneity of the current distribution, particularly at lower currents and lower air-flow rates. Among these three variations, increased loading near the lateral areas was shown to contribute most to achieving a homogenous current distribution. The mechanism underlying each catalyst loading variation method is different; very high catalyst-loading is shown to decrease the homogeneity of the distribution, which may be caused by water management in the thick catalyst layer thereof.

NUMERICAL STUDY ON THE EROSION CHARACTERISTICS OF SCR CATALYST DUCT BY VARYING ITS GEOMETRICAL CONFIGURATION (SCR 촉매층 형상변화에 따른 침식특성에 관한 수치해석적 연구)

  • Park, Hun-Chae;Choi, Hang-Seok;Choi, Yeon-Seok
    • Journal of computational fluids engineering
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    • v.16 no.2
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    • pp.66-74
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    • 2011
  • The SCR catalyst in coal-fired power plant is eroded by the collision of fly ash on the catalyst surface. However the erosion of SCR catalyst by the collision of fly ash has not been fully studied, especially in terms of fluid dynamics. Hence, in the present study, we focus on the gas and solid flows inside the SCR catalyst duct and their consequent effect on the erosion characteristics. For this purpose, computational fluid dynamics is applied to investigate the two-phase flows and to evaluate the erosion rate for different flow and particle injection conditions. Also, the erosion rate and pressure drop of commonly used square shape are compared with equilateral triangle and hexagon shapes. The pressure drop of SCR catalyst is increased when SCR catalyst surface area per unit volume increases. The erosion rate of SCR catalyst is enhanced when the particle velocity, mass flow rate of particle, particle diameter and cell density of SCR catalyst are increased. From the results, the pressure drop and erosion rate at the catalyst surface can be minimized by reducing cell density of SCR catalyst to decrease particle velocity and number of particle impacts.

Effect of the Ni Catalyst Size and Shape on the Variation of the Geometries for the As-grown Carbon Coils

  • Jang, Chang-Young;Kim, Sung-Hoon
    • Journal of the Korean institute of surface engineering
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    • v.46 no.4
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    • pp.175-180
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    • 2013
  • Carbon nanofilaments (CNFs) could be synthesized using $C_2H_2/H_2$ as source gases and $SF_6$ as an incorporated additive gas under thermal chemical vapor deposition system. Ni powders were used as the catalyst for the formation of the CNFs. During the initial deposition stage, the initiation of the CNFs on the Ni catalyst was investigated. The geometries of the as-grown CNFs on Ni catalyst were strongly dependent on the size and/or the shape of Ni catalyst. Small size catalyst (<150 nm in diameter) gives rise to the unidirectional growth of the CNFs. On the other hand, large size catalyst (150~500 nm), the bidirectional growth of the CNFs could be observed. Particularly, the well faceted parallelogram-shaped Ni catalyst could give rise to the bidirectional growth of the CNFs having the symmetrically opposite direction. Eventually, these bidirectional growths of CNFs were understood to form the well-developed carbon microcoils (CMCs). Based on these results, the optimal shape and the size of the Ni catalyst to form the CMCs were discussed.

Nitrogen doped graphene/cobalt-based catalyst layers of a PEM fuel cell: Performance evaluation and multi-objective optimization

  • Kazeminasab, Bagher;Rowshanzamir, Soosan;Ghadamian, Hossein
    • Korean Journal of Chemical Engineering
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    • v.34 no.11
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    • pp.2978-2983
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    • 2017
  • The proton exchange membrane fuel cell could be made more commercially viable by substituting the expensive platinic catalyst without loss of performance. This should be done simultaneously through optimization and use of a non-precious metal catalyst. In this study, multi-objective optimization of the catalyst layer was done on nonprecious metal catalysts. Nitrogen-doped graphene (NG)-based cobalt was synthesized as a non-precious metal catalyst. Differential equations were solved at the modeling stage by the shooting method, and objective functions were solved at the optimization stage using sequential quadratic programming. NG-based cobalt was evaluated in a cell and then compared with the platinum catalyst. Results present the synthesized non-precious catalyst as an appropriate replacement for existing precious metal catalyst. Also, the polarization curve demonstrates that the current modeling is in good agreement with NG-based cobalt catalyst. Finally, the Pareto curve at the voltage of 0.6 V (and $300A/m^2$ current density in the base case) indicated that the best tradeoff between cost and performance of the catalyst layer was achieved when the current density was increased in the range of 5% to 15%.

Charateristics of Hydrogen Iodide Decomposition using Ni-Pt Bimetallic Catalyst in Sulfur-Iodine Process (황-요오드 열화학 수소 생산 공정에서 니켈-백금 이원금속 촉매를 이용한 요오드화수소 분해 특성)

  • Kim, Soo-Young;Go, Yoon-Ki;Park, Chu-Sik;Bae, Ki-Kwang;Kim, Young-Ho
    • Transactions of the Korean hydrogen and new energy society
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    • v.23 no.1
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    • pp.1-7
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    • 2012
  • This study was performed to develop a low Pt content catalyst as a catalyst for HI decomposition in S-I process. Bimetallic catalysts added various amounts of Pt on a silica supported Ni catalyst were prepared by impregnation method. HI decomposition was carried out using a fixed bed reactor. As a result, Ni-Pt bimetallic catalyst showed enhanced catalytic activity compared with each monometallic catalyst. Deactivation of Ni-Pt catalyst was not observed while deactivation of Ni monometallic catalyst was rapidly occurred in HI decomposition. The HI conversion of Ni-Pt bimetallic catalyst was increased similar to Pt catalyst with increase of the reaction temperature over a temperature range 573K to 773K. From the TG analysis, it was shown that $NiI_2$ remained on the Ni(5.0)-Pt(0.5)/$SiO_2$ catalyst after the HI decomposition reaction was decomposed below 700K. It seems that small amount of Pt in bimetallic catalyst increase the decomposition of $NiI_2$ generated after the decomposition of HI. Consequently, it was considered that the activity of Ni-Pt bimetallic catalyst was kept during the HI decomposition reaction.

A Study on the Possibility of Using of Spent RHDS Catalyst as a SCR Catalyst wash-coated on the metal corrugated substrate (폐 RHDS 촉매재생 후 메탈 코로게이트 지지체상에서 워시코팅에 의한 NOx 저감 SCR 촉매에 관한 연구)

  • Na, Woo-jin;Cha, Eunji;Kang, Dae-hwan;Go, Young-ju;Cho, Ye-ji;Choi, Eun-young;Park, Hea-Kyung
    • Journal of the Korean Applied Science and Technology
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    • v.37 no.4
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    • pp.723-732
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    • 2020
  • The spent RHDS (Residue HydroDeSulfurization) catalyst is deactivated mainly by deposition of various contaminants such as coke, sulfur and vanadium on the surface of catalyst. To eliminate those contaminants, the following remanufacturing process was conducted. The first, heavy oil on the surface of the spent RHDS catalyst was removed by kerosene and dehydrated. The second, the high temperature incineration was carried out to eliminate coke and sulfur components deposited on the surface of spent RHDS catalyst. The third, the excessive quantity of Vanadium deposited on the surface of catalyst was removed by leaching process as follows: ultrasonic agitation was carried out at 50℃, for 10 seconds with 0.5% and 1% oxalic acid solution. The purpose of this process is to find out regenerated RHDS catalyst can be used as SCR catalyst for NOx reduction by controlling the vanadium residual content of the regenerated RHDS catalyst through leaching process. The composition of regenerated RHDS catalyst was analyzed by XRF and the NOx reduction efficiency was also measured by continuous catalytic fixed bed reactor. As the result, regenerated catalyst, with 0.5% oxalic acid, ultrasonic agitation in 10 seconds, showed the most stable NOx reduction efficiency. Also, in comparison with commercial SCR catalyst, the NOx reduction performance of regenerated catalyst was similar to that of commercial SCR catalyst at the temperature 375℃ and higher whereas was lower than commercial SCR catalyst at the temperature range between 200~250℃. Therefore, it was confirmed that the regenerated catalyst as powder form wash coated on the surface of metal corrugated substrate can be used for commercial SCR catalyst.