• Title/Summary/Keyword: Charge Transfer Resistance

Search Result 155, Processing Time 0.029 seconds

Effect of Iodine-coated Bipolar Plates on the Performance of a Polymer Exchange Membrane (PEM) Fuel Cell (고분자 전해질 막 연료전지에서의 아이오딘이 코팅된 분리판의 성능 효과)

  • Kim, Taeeon;Juon, Some;Cho, Kwangyeon;Shul, Yonggun
    • Transactions of the Korean hydrogen and new energy society
    • /
    • v.24 no.1
    • /
    • pp.61-69
    • /
    • 2013
  • Polymer exchange membrane (PEM) fuel cells have multifunctional properties, and bipolar plates are one of the key components in these fuel cells. Generally, a bipolar plate has a gas flow path for hydrogen and oxygen liberated at the anode and cathode, respectively. In this study, the influence of iodine applied to a bipolar plate was investigated. Accordingly, we compared bipolar plates with and without iodine coating, and the performances of these plates were evaluated under operating conditions of $75^{\circ}C$ and 100% relative humidity. The membrane and platinum-carbon layer were affected by the iodine-coated bipolar plate. Bipolar plates coated with iodine and a membrane-electrode assembly (MEA) were investigated by electron probe microanalyzer (EPMA) and energy-dispersive x-ray spectroscopy (EDS) analysis. Polarization curves showed that the performance of a coated bipolar plate is approximately 19% higher than that of a plate without coating. Moreover, electrochemical impedance spectroscopy (EIS) analysis revealed that charge transfer resistance and membrane resistance decreased with the influence of the iodine charge transfer complex for fuel cells on the performance.

Preparations and Electrochemical Characteristics of Polypyrrole by Constant Potential Electroplymerization (정전위 전해 중합법에 의한 폴리피롤 제조 및 전기화학적 특성)

  • Cho, Seung-Koo;Sim, Chol-Ho
    • Journal of the Korean Electrochemical Society
    • /
    • v.8 no.2
    • /
    • pp.99-105
    • /
    • 2005
  • In this study, the $PPy/CLO_4$ and PPy/PVS composite electrodes were prepared at various polymerization potential by incorporating electrolyte anions of different anion size during constant potential polymerization. The reulting Polypyrrole surfaces were inspected by SEM, and their electrochemical Properties were investigated with CV and ac impedance method. The results of electrochemical analysis were suggested that anion for $PPy/CLO_4$ electrode and cation fir PPy/PVS electrode were transferred during redox reaction. As constant potential of polymerization was increased, the charge transfer resistance of $PPy/CLO_4$ and PPy/PVS was decreased and the electric double layer capacitances of $PPy/CLO_4$ was higher than that of PPy/PVS. The change of PPy/PVS surface was relatively smaller than that of $PPy/CLO_4$ according to electropolymerization potential.

Performance Test of Low Temperature Waste Heat Recovery Heat Exchanger Using Self-excited Oscillating Heat Pipe (자려 진동형 히트 파이프를 이용한 저온 폐열 회수 열교환기의 성능 실험)

  • 이욱현;이종현;김종수
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.12 no.9
    • /
    • pp.853-859
    • /
    • 2000
  • In this study, low temperature waste heat recovery heat exchanger was developed using a principle of self-excited oscillating heat pipe. The heat exchanger of serpentine type was composed of extruded flat aluminum tube with 6 channels (3 nm$\times$ 2.75nm) and louvered fin. The heat transfer area density of heat exchanger was $331.9 m^2/m^3$. Working fluid is R141b and charge ratio was 40% by volume. Heat transfer rate and the effectiveness of heat exchanger was primary concern of this study. As a result, the effectiveness of heat exchanger was about 0.4-0.67, and recovered waste heat rate was about 4.5 kW per one unit of heat exchanger.

  • PDF

New Polymer Electrolytes for Solid State Dye-Sensitized Solar Cells (고분자 전해질을 이용한 고체형 염료감응 태양전지)

  • Kang, Yong-Soo;Lee, Yong-Gun;Kang, Moon-Sung;Kim, Jong-Hak;Char, Kook-Chen
    • 한국신재생에너지학회:학술대회논문집
    • /
    • 2007.06a
    • /
    • pp.231-234
    • /
    • 2007
  • The solid state dye-sensitized saolrc cells (DSSCs) employing polymer electrolytes show high overall energy conversion efficiency as high as 4.5% at 1 sun conditions. The improved efficiency may be primarily due to the enlarged interfacial contact area between the electrolyte and dyes in addition to the increased ionic conductivity, which were done by utilizing liquid oligomers, followed by in situ self-solidification, to form the solid DSSCs "Oligomer Approach". The effect of the charge transfer resistance at the counter electrode side on the effciency has also been investigated.

  • PDF

Corrosion Evaluation of Epoxy-Coated Bars by Electrochemical Impedance Spectroscopy

  • Choi, Oan-Chul;Park, Young-Su;Ryu, Hyung-Yun
    • International Journal of Concrete Structures and Materials
    • /
    • v.2 no.2
    • /
    • pp.99-105
    • /
    • 2008
  • Southern exposure test specimens were used to evaluate corrosion performance of epoxy-coated reinforcing bars in chloride contaminated concrete by electrochemical impedance spectroscopy method. The test specimens with conventional bars, epoxy-coated bars and corrosion inhibitors were subjected 48 weekly cycles of ponding with sodium chloride solution and drying. The polarization resistance obtained from the Nyquist plot was the key parameter to characterize the degree of reinforcement corrosion. The impedance spectra of specimens with epoxy-coated bars are mainly governed by the arc of the interfacial film and the resistance against the charge transfer through the coating is an order of magnitude higher than that of the reference steel bars. Test results show good performance of epoxy-coated bars, although the coatings had holes simulating partial damage, and the effectiveness of corrosion-inhibiting additives. The corrosion rate obtained from the impedance spectroscopy method is equivalent to those determined by the linear polarization method for estimating the rate of corrosion of reinforcing steel in concrete structures.

Enhancement of Electrolyte Properties for High Energy Density Supercapacitors by using Additive Materials

  • Kim, Cheong;Habazaki, Hiroki;Park, Soo Gil
    • Journal of Electrochemical Science and Technology
    • /
    • v.7 no.3
    • /
    • pp.214-217
    • /
    • 2016
  • In this study, we studied the enhancement of the energy densities of electrochemical capacitors by improving the working voltage range of the electrolyte. To prevent the decomposition of the electrolyte, stable SEI layers were formed by reductive degradation of additive materials such as fluoro-ethylene carbonate (FEC) and vinyl ethylene carbonate (VEC) before degradation of the base electrolyte. As a result, the solution resistance (Rs) of EC:DMC + SL 20 % + VEC 1 % electrolytes observed 1.47 Ω and the charge transfer resistance (Rct) was 2.64 Ω at the open circuit voltage. Additionally, a cycle retention of 94 % was observed for EC:DMC + SL 20 % + VEC 1 % after 500 cycles at 3.5 V.

Study on a Operating Characteristics of Loop Heat Pipe Using a Brass Sintered Metal Wick-Water (황동소결윅-물 LHP의 작동 특성에 관한 연구)

  • Lee, Wook-Hyun;Lee, Ki-Woo;Park, Ki-Ho;Lee, Kye-Jung;Noh, Seung-Young
    • Proceedings of the KSME Conference
    • /
    • 2004.04a
    • /
    • pp.1528-1533
    • /
    • 2004
  • In this study, we have manufactured the LHP(Loop Heat Pipe) with sintered metal wick and investigated the working characteristics of LHP experimentally.Water was used as a working fluid and fill charge rate was changed. LHP basically consist of the separated vapor/liquid channels, evaporator having sintered metal wick(effective pore diameter :$16{\sim}19{\mu}m$), and condenser cooled by water. The diameter of vapor/liquid line tube are 3.2mm/6.35mm, respectively. Heat transfer rate and thermal resistance was represented to study the basic characteristics of LHP at each conditions

  • PDF

Effect of electropolishing process time on electrochemical characteristics in seawater for austenitic stainless steel (오스테나이트 스테인리스강의 해수에서 전기화학적 특성에 미치는 전해연마시간의 영향)

  • Hwang, Hyun-Kyu;Shin, Dong-Ho;Heo, Ho-Seong;Kim, Seong-Jong
    • Journal of the Korean institute of surface engineering
    • /
    • v.55 no.4
    • /
    • pp.236-246
    • /
    • 2022
  • Electropolishing is a surface finishing treatment that compensates for the disadvantages of the mechanical polishing process. It not only has a smooth surface, but also improves corrosion resistance. Therefore, the purpose of this investigation is to examine the corrosion resistance and electrochemical characteristics in seawater of UNS S31603 with electropolishing process time. The roughness improvement rate after electropolishing was improved by about 78% compared to before polishing, indicating that the electropolishing is effective. As a result of potential measuring of mechanical polishing and electropolishing, the potential of electropolishing was nobler than the mechanical polishing condition. As a result of calculating the corrosion current density after potentiodynamic polarization experiment with electropolishing conditions, the corrosion current density of mechanical polishing was about 6.4 times higher than that of electropolishing. After potentiodynamic polarization experiment with electropolishing conditions, the maximum damage depth of mechanical polishing was about 2.2 times higher than that of electropolishing(7 minutes). In addition, the charge transfer resistance of the specimen electropolished for 7 minutes was the highest, indicating improved corrosion resistance.

Photoelectrochamical characteristics of $WO_3$ on metal substrate for hydrogen production (텅스텐산화물/금속기판의 광전극 특성)

  • Go, GeunHo;Shinde, Pravin S.;Seo, SeonHee;Lee, Dongyoon;Lee, Wonjae
    • 한국신재생에너지학회:학술대회논문집
    • /
    • 2011.11a
    • /
    • pp.99.2-99.2
    • /
    • 2011
  • Transparent conducting oxides (TCOs) supported on glass are widely used as substrates in PEC studies for photovoltaic hydrogen generation applications However, high sheet resistane ($10{\sim}15{\Omega}/cm^2$) and fragileness of glass-supported TCO substrates are the obstacles to produce the large area PEC cells. Such internal sheet resistance is detrimental to efficient collection of photogenerated majority charge carriers at the photoactive material and electrolyte interface. Moreover, these TCO substrates are very expensive and consume about 40~60% cost of the devices. Hence, a low sheet resistance of the substrate is a key point in improving the performance of PEC devices. Metallic substrates coated with a photoactive material would be a good choice for efficient charge collection. Such metal substrates based photanodes are best candidate for large-scale phtoelectrochemical water splitting for hydrogen generation. In this study, we report the enhanced PEC performance of $WO_3$ film on metal(chemical etched, bare) substrate. It is proposed that interface between $WO_3$ and the metal substrate is responsible for efficient charge transfer and demonstrated significant improvement in the photoelectrochmical performance. X-ray diffration and FESEM suduies reveled that $WO_3$ films are monoclinic, porous, polycrystalline with average grain size of ~50nm. Photocurrent of $WO_3$ prepared on metal substrates was measured in 0.5M $H_2SO_4$ electroyte under simulated $100mW/cm^2$ illumination.

  • PDF

Degradation Mechanisms of a Li-S Cell using Commercial Activated Carbon

  • Norihiro Togasaki;Aiko Nakao;Akari Nakai;Fujio Maeda;Seiichi Kobayashi;Tetsuya Osaka
    • Journal of Electrochemical Science and Technology
    • /
    • v.14 no.4
    • /
    • pp.361-368
    • /
    • 2023
  • In lithium-sulfur (Li-S) batteries, encapsulation of sulfur in activated carbon (AC) materials is a promising strategy for preventing the dissolution of lithium polysulfide into electrolytes and enhancing cycle life, because instead of solid-liquid-solid reactions, quasi-solid-state (QSS) reactions occur in the AC micropores. While a high weight fraction of sulfur in S/AC composites is essential for achieving a high energy density of Li-S cells, the deterioration mechanisms under such conditions are still unclear. In this study, we report the deterioration mechanisms during charge-discharge cycling when the discharge products overflow from the AC. Analysis using scanning electron microscopy and energy-dispersive X-ray spectrometry confirms that the sulfur in the S/AC composites migrates outside the AC as cycling progresses, and it is barely present in the AC after 20 cycles, which corresponds to the capacity decay of the cell. Impedance analysis clearly shows that the electrical resistance of the S/AC composite and the charge-transfer resistance of QSS reactions significantly increase as a result of sulfur migration. On the other hand, the charge-discharge cycling performance under limited-capacity conditions, where the discharge products are encapsulated inside the AC, is extremely stable. These results reveal the degradation mechanism of a Li-S cell with micro-porous carbon and provide crucial insights into the design of a S/AC composite cathode and its operating conditions needed to achieve stable cycling performance.