• Title/Summary/Keyword: Polymer electrolyte membrane

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Synthesis of Carbon Nanotubes Supported PtCo Electrocatalysts and Its Characterization for the Cathode Electrode of PEMFC (탄소나노튜브에 담지된 PtCo 촉매 제조 및 PEMFC Cathode 전극 특성)

  • Jung, Dong-Won;Park, Soon;Kang, Jung-Tak;Kim, Jun-Bom
    • Korean Journal of Materials Research
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    • v.19 no.5
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    • pp.233-239
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    • 2009
  • The electrocatalytic behavior of the PtCo catalyst supported on the multi-walled carbon nanotubes (MWNTs) has been evaluated and compared with commercial Pt/C catalyst in a polymer electrolyte membrane fuel cell(PEMFC). A PtCo/MWNTs electrocatalyst with a Pt:Co atomic ratio of 79:21 was synthesized and applied to a cathode of PEMFC. The structure and morphology of the synthesized PtCo/MWNTs electrocatalysts were characterized by X-ray diffraction and transmission electron microscopy. As a result of the X-ray studies, the crystal structure of a PtCo particle was determined to be a face-centered cubic(FCC) that was the same as the platinum structure. The particle size of PtCo in PtCo/MWNTs and Pt in Pt/C were 2.0 nm and 2.7 nm, respectively, which were calculated by Scherrer's formula from X-ray diffraction data. As a result we concluded that the specific surface activity of PtCo/MWNTs is superior to Pt/C's activity because of its smaller particle size. From the electrochemical impedance measurement, the membrane electrode assembly(MEA) fabricated with PtCo/MWNTs showed smaller anodic and cathodic activation losses than the MEA with Pt/C, although ohmic loss was the same as Pt/C. Finally, from the evaluation of cyclic voltammetry(CV), the unit cell using PtCo/MWNTs as the cathode electrocatalyst showed slightly higher fuel cell performance than the cell with a commercial Pt/C electrocatalyst.

HI concentration by EED for the HI decomposition in IS process (IS 프로세스의 HI 분해반응공정을 위한 전해 - 전기투석(EED) HI 농축)

  • Hong, Seong-Dae;Kim, Jeong-Geun;Lee, Sang-Ho;Choi, Sang-Il;Bae, Ki-Kwang;Hwang, Gab-Jin
    • Transactions of the Korean hydrogen and new energy society
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    • v.17 no.2
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    • pp.212-217
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    • 2006
  • An experimental study on Electro-electrodialysis (EED) for IS (Iodine-Sulfur) process which is well known as hydrogen production system was carried out for the HI concentration from HIx (HI: $H_2O$ : $I_2$ = 1 : 5 : 1) solution. The polymer electrolyte membrane and the activated carbon cloth were adopted as a cation exchange membrane and electrode, respectively. In order to evaluate the temperature effect about HI concentration in fixed molar ratio, three case of temperature were selected to $60^{\circ}C$, $90^{\circ}C$ and $120^{\circ}C$. The electro-osmosis coefficient and transport number of proton have been changed from 1.95 to 1.21 (mol/Faraday) and 0.91 to 0.76, respectively as temperature increase from $60^{\circ}C$ to $120^{\circ}C$. It can be realized that the HI mole fraction in final stage of EED experiments already over the quasi-azeotrope composition.

Analysis of the Effects of CO Poisoning and Air Bleeding on the Performance of a PEM Fuel Cell Stack using First-Order System Model (일차계 모델을 이용한 고분자전해질 연료전지 스택의 CO Poisoning 및 Air Bleeding 효과 분석)

  • Han, In-Su;Shin, Hyun Khil
    • Korean Chemical Engineering Research
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    • v.51 no.3
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    • pp.370-375
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    • 2013
  • We analyze the effects of CO poisoning and air bleeding on the performance of a PEM (polymer electrolyte membrane) fuel cell stack fabricated using commercial MEA (membrane electrode assembly). Dynamic response data from the experiments on the performance of a stack are identified by obtaining steady-state gains and time-constants of the first-order system model expressed as a first-order differential equation. It is found that the cell voltage of the stack decreases by 1.3-1.6 mV as the CO concentration rises by 1 ppm. The time elapsed to reach a new steady state after a change in the CO concentration is shortened as the magnitude of the change in the CO concentration increases. In general, the steady-state gain becomes bigger and the time-constant gets smaller with increasing the air concentration (air-bleeding level) in the reformate gas to restore the cell voltage. However, it is possible to recover 87%-96% of the original cell voltages, which are measured with free of CO, within 1-30 min by introducing the bleed air as much as 1% of the reformate gas into the stack.

Metal Foam Flow Field Effect on PEMFC Performance (금속 폼 유로가 고분자전해질 연료전지 성능에 미치는 영향)

  • Kim, Junseob;Kim, Junbom
    • Applied Chemistry for Engineering
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    • v.32 no.4
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    • pp.442-448
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    • 2021
  • Flow field is an important parameter for polymer electrolyte membrane fuel cell (PEMFC) performance to have an effect on the reactant supply, heat and water diffusion, and contact resistance. In this study, PEMFC performance was investigated using Cu foam flow field at the cathode of 25 cm2 unit cell. Polarization curve and electrochemical impedance spectroscopy were performed at different pressure and relative humidity conditions. The Cu foam showed lower cell performance than that of serpentine type due to its high ohmic resistance, but lower activation and concentration loss due to the even reactant distribution of porous structure. Cu foam has the advantage of effective water transport because of its hydrophobicity. However, it showed low membrane hydration at low humidity condition. The metal foam flow field could improve fuel cell performance with a uniform pressure distribution and effective water management, so future research on the properties of metal foam should be conducted to reduce electrical resistance of bipolar plate.

Optimization Method for MEA Performance Considering the Non-Uniformity of Operating Condition in a Large-area Bipolar Plate (대면적 분리판의 운전 환경 불균일성을 고려한 MEA 성능최적화 방법)

  • Kim, Sungmin;Sohn, Young-Jun;Woo, Seunghee;Park, Seok-Hee;Jung, Namgee;Yim, Sung-Dae
    • New & Renewable Energy
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    • v.17 no.2
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    • pp.50-58
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    • 2021
  • We proposed an MEA development methodology that accurately measures intrinsic MEA performance while considering the uneven reaction environments formed inside a large-area BP. To facilitate measurement of the inherent MEA performance, we miniaturized the active area of the MEA to 3 cm2, and prepared two MEAs with different ionomer contents of 0.65 and 0.80 (I/C). By simulating the operating conditions of a 100 cm2 BP at the inlet (I), center (C), and outlet (O), the oxygen concentration and relative humidity were determined to be 20.7, 13.8, 11.7%, and 50, 66.1, and 70.1% respectively. We measured the performance and electrochemical analysis of the prepared MEAs under the three simulated conditions. Based on the results of statistical analysis of the evaluated MEA performance data, I/C 0.65 MEA had a higher average performance and lower performance deviation than I/C 0.80 MEA. Hence, it can be concluded that an I/C 0.65 MEA is a more effective MEA for large-area BP. Based on the above research process, we confirmed the effectiveness of the proposed MEA development methodology.

Self-pressurization Effect and PEMFC Performance Improvement Using Metal Foam Compression (금속 폼 압축에 의한 자가 가압 효과 및 PEMFC 성능 개선)

  • Kim, Hyeonwoo;Kim, Junbom
    • Applied Chemistry for Engineering
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    • v.33 no.6
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    • pp.618-623
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    • 2022
  • The bipolar plate is a key component of the polymer electrolyte membrane fuel cell (PEMFC) that transfers reactants and electrons, discharges water and heat as by-products, and serves as a mechanical support for the membrane electrode assembly (MEA). Therefore, the flow field structure of the bipolar plate plays an important role in improving fuel cell performance. In this study, PEMFC performance was investigated with copper foams with different compressibility ratios applied to cathode bipolar plates using a 25 cm2 unit cell. The total resistance decreased as the compressibility ratio of the metal foams increased, and, in particular, the charge transfer and mass transfer resistance were significantly improved compared to the serpentine flow field, lowering voltage loss in medium and high current density region. In the case of pressurized air reactant flow with serpentine structure, fuel cell performance was similar to that of a compressed metal foam flow field (S3) up to the medium current density region, but low performance appeared in the high current density region due to flow field structure limitations.

The Comparison of Activation Protocols for PEMFC MEA with PtCo/C Catalyst (PtCo/C 촉매를 사용한 PEMFC MEA의 활성화 프로토콜 비교)

  • GISEONG LEE;HYEON SEUNG JUNG;JINHO HYUN;CHANHO PAK
    • Transactions of the Korean hydrogen and new energy society
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    • v.34 no.2
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    • pp.178-186
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    • 2023
  • Three activation methods (constant voltage, current cycling, and hydrogen pumping) were applied to investigate the effects on the performance of the membrane electrode assembly (MEA) loaded with PtCo/C catalyst. The current cycling protocol took the shortest time to activate the MEA, while the performance after activation was the worst among the all activation methods. The constant voltage method took a moderate activation time and exhibited the best performance after activation. The hydrogen pumping protocol took the longest time to activate the MEA with moderate performance after activation. According to the distribution of relaxation time analysis, the improved performance after the activation mainly comes from the decrease of charge transfer resistance rather than the ionic resistance in the cathode catalyst layer, which suggests that the existence of water on the electrode is the key factor for activation.

Aging Property Studies on Rubber Gasket for Polymer Electrolyte Membrane Fuel Cell Stack (고분자 전해질 연료전지 스택용 고무 개스킷의 노화특성 연구)

  • Kang, Dong-gug;Hur, Byung-ki;Lee, Dong-won;Seo, Kwan-ho
    • Applied Chemistry for Engineering
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    • v.22 no.2
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    • pp.149-154
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    • 2011
  • In order to explore properties of various rubber compounds after thermal aging under the condition similar to the operating environment of a fuel cell-stack, heat resistance and compression set of those compounds were investigated for a long term operation in $H_2SO_4$, $H_2O$, and LLC (ethylene glycol : $H_2O=50:50$) solution. It was assumed that aging Acrylonitrile butadiene rubber (NBR) and Elthylene Propylene diene rubber (EDPM) compound in the solution resulted in discoloration as time passed. It was also found that hydrolysis was developed on the Silicone rubber (VMQ) compound intentionally aged under acidic condition by means of TGA, SEM, and EDS analysis.

Preparation and Characterization of Proton Conducting Crosslinked Membranes Based On Poly(vinyl chloride) Graft Copolymer (Poly(vinyl chloride) 가지형 공중합체를 이용한 수소이온 전도성 가교형 전해질막의 제조와 분석)

  • Kim, Jong-Hak;Koh, Jong-Kwan;Choi, Jin-Kyu;Park, Jung-Tae;Koh, Joo-Hwan
    • Membrane Journal
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    • v.18 no.4
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    • pp.261-267
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    • 2008
  • A graft copolymer consisting of poly(vinyl chloride) (PVC) backbone and poly(hydroxyethyl acrylate) (PHEA) side chains was synthesized via atom transfer radical polymerization (ATRP). Direct initiation of the secondary chlorines of PVC facilitates grafting of hydrophilic PHEA monomer. This graft copolymer, i.e. PVC-g-PHEA was cross-linked with sulfosuccinic acid (SA) via the esterification reaction between -OH of the graft copolymer and -COOH of SA, as confirmed by FT-IR spectroscopy. Ion exchange capacity (IEC) continuously increased to 0.87meq/g with increasing concentrations of SA, due to the increasing portion of charged groups in the membrane. However, the water uptake increased up to 20.0wt% of SA concentration above which it decreased monotonically. The membrane also exhibited a maximum proton conductivity of 0.025 S/cm at 20.0 wt% of SA concentration, which is presumably due to competitive effect between the increase of ionic sites and the crosslinking reaction.

Stabilization of Covalently Cross-Linked SPEEK/Cs-Substituted HPA Composite Membranes for Water Electrolysis ($Cs^+$치환에 따른 수전해용 공유가교 SPEEK/HPA 복합막의 안정화)

  • Jee, Bong-Chul;Ha, Sung-In;Song, Min-Ah;Chung, Jang-Hoon;Moon, Sang-Bong;Kang, An-Soo
    • Transactions of the Korean hydrogen and new energy society
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    • v.22 no.1
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    • pp.1-12
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    • 2011
  • To improve the mechanical properties, such as durabilities and antioxidative characteristics, the covalently cross-linked (CL-) SPEEK (sulfonated polyether ether ketone)/Cs-substituted HPA (heteropoly acid) organic-inorganic composite membranes (CL-SPEEK/Cs-HPAs), have been intensively investigated. The composite membrane were prepared by blending cesium-substituted HPAs (Cs-HPAs), including tungstophosphoric acid (TPA), molybdophosphoric acid (MoPA), and tungstosilicic acid (TSiA) with cross-linking agent content of 0.01 mL. And composite electrolytes composed of Cs-HPAs, prepared by immersion (imm.) and titration (titr.) methods to increase the stability of HPAs in water, were applied to polymer electrolyte membrane electrolysis (PEME). As a result, the proton conductivity of Cs-substituted composite membranes increased rapidly over $60^{\circ}C$ but mechanical properties, such as tensile strength, decreased in accordance with added Cs content. The bleeding-out of Cs-TPA membranes by titration method (50 vol.% Cs) decreased steadily to 2.15%. In the oxidative stability test by Fenton solution, the durability of membranes with Cs-HPA significantly increased. In case of CL-SPEEK/ Cs-TPA membrane, duration time increased more than 1200 hours. It is expected that even though CL-SPEEK/Cs-MoPA membrane shows the high proton conductivity, electrocatalytic activity and cell voltage of 1.80 V for water electrolysis, the CL-SPEEK/Cs-TPA (imm.) is more suitable as an alternative membrane in real system with the satisfactory proton conductivity, mechanical properties, anti-oxidative stability and cell voltage of 1.89 V.