• Title, Summary, Keyword: Proton conductivity

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Proton Conducting Behavior of a Novel Composite Based on Phosphosilicate/Poly(Vinyl Alcohol)

  • Huang, Sheng-Jian;Lee, Hoi-Kwan;Kang, Won-Ho
    • Journal of the Korean Ceramic Society
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    • v.42 no.2
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    • pp.77-80
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    • 2005
  • A series of proton conductive composite membranes based on poly(vinyl alcohol) and phosphosilicate gels powders were successfully prepared. The proton conductivity of these composite was attributed to the phosphosilicate gel, which derived from tetraethoxysilane and phosphoric acid by sol-gel process at a molar ratio of P/Si = 1.5. The proton conductivity increased with increasing both the content of phosphosilicate gel and relative humidity. Temperature dependence of conductivity showed a Vogel-Tamman-Fulcher type behavior, indicating that proton was transferred through a liquidlike phase formed in micropores of phosphosilicate gel. The high conductivity of 0.065 S/cm with a membrane containing 60 wt$\%$ of the gel was obtained at $60^{\circ}C$ at $90\%$ relative humidity.

Proton Conductivity Measurement Using A.C. Impedance Spectroscopy for Proton Exchange Membrane

  • Lee, Chang Hyun;Park, Ho Bum;Lee, Young Moo
    • Korean Membrane Journal
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    • v.6 no.1
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    • pp.1-9
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    • 2004
  • The impedance and the subsequent proton conductivity of Nafion$\^$/ membranes as standard samples were measured and compared via the two-probe method and the four-probe method using the prepared impedance measurement system. The different impedance behavior for the same membrane was observed at the fully hydrated state in the Nyquist impedance plot. The effect of the humidity and the temperature on the proton conduction through a membrane was investigated and compared with two different cell configurations.

Low-Temperature Characterization of Domain Wall Dynamics and Electrical Conduction in a Proton-Irradiated K(H0.21D0.79)2PO4 System

  • Lee, Cheol Eui;Oh, Byoung Hoo;Kim, Se-Hun
    • New Physics: Sae Mulli
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    • v.67 no.2
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    • pp.232-236
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    • 2017
  • We investigated the longitudinal electrical conductivity associated with the domain-wall dynamics in proton-irradiated $K(H_{0.21}D_{0.79})_2PO_4$ single crystals a temperatures below room temperature. Frequency-dependent longitudinal dielectric-loss measurements allowed us to investigate the changes in the domain-wall dynamics of the proton-irradiated crystal with a ferroelectric phase-transition temperature increase of 8 K. Using the Vogel-Fulcher function, we found that proton irradiation produced a slight increase in the activation energy of domain freezing. The temperature dependence of the power-law exponent n in frequency-dependent electrical conductivity in proton-conducting systems decreased at temperatures near the phase-transition temperature $T_{c2}$. In addition, the temperature dependence of the electrical conductivity shifted to higher temperatures because of the increased phase-transition temperature arising from the proton irradiation.

Cerium Pyrophosphate-based Proton-conducting Ceramic Electrolytes for Low Temperature Fuel Cells

  • Singh, Bhupendra;Kim, Ji-Hye;Im, Ha-Ni;Song, Sun-Ju
    • Journal of the Korean Ceramic Society
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    • v.51 no.4
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    • pp.248-259
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    • 2014
  • Acceptor-doped cerium pyrophosphates have shown significant proton conductivity of > $10^{-2}Scm^{-1}$ in the range of $100-300^{\circ}C$ and are considered promising candidates for use as electrolytes in proton-conducting, ceramic electrolyte fuel cells (PCFCs). But, cerium pyrophosphates themselves do not have structural protons, and protons incorporate into their material bulk only as impurities on exposure to a hydrogen-containing atmosphere. However, proton incorporation and proton conduction in these materials are expected to be affected by factors such as the nature (ionic size and charge) and concentration of the aliovalent dopant, processing history (synthesis route and microstructure), and the presence of residual phosphorous phosphate ($P_mO_n$) phases. An exact understanding of these aspects has not yet been achieved, leading to large differences in the magnitude of proton conductivity of cerium pyrophosphates reported in various studies. Herein, we systematically address some of these aspects, and present an overview of factors affecting proton conductivity inacceptor-doped $CeP_2O_7$.

Proton Conductivity of Niobium Phosphate Glass Thin Films

  • Kim, Dae Ho;Park, Sung Bum;Park, Yong-il
    • Korean Journal of Materials Research
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    • v.28 no.5
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    • pp.308-314
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    • 2018
  • Among the fuel cell electrolyte candidates in the intermediate temperature range, glass materials show stable physical properties and are also expected to have higher ion conductivity than crystalline materials. In particular, phosphate glass has a high mobility of protons since such a structure maintains a hydrogen bond network that leads to high proton conductivity. Recently, defects like volatilization of phosphorus and destruction of the bonding structure have remarkably improved with introduction of cations, such as Zr4+ and Nb5+, into phosphate. In particular, niobium has proton conductivity on the surface because of higher surface acidity. It can also retain phosphorus content during heat treatment and improve chemical stability by bonding with phosphorus. In this study, we fabricate niobium phosphate glass thin films through sol-gel processing, and we report the chemical stability and electrical properties. The existence of the hydroxyl group in the phosphate is confirmed and found to be preserved at the intermediate temperature region of $150-450^{\circ}C$.

Synthesis and Characterization of Sulfonated Poly(phthalazinone ether sulfone)(sPPES)/Silica Membrane for Proton Exchange Membrane Materials

  • Kim, Dae Sik;Park, Ho Bum;Nam, Sang Young;Rhim, Ji Won;Lee, Young Moo
    • Korean Membrane Journal
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    • v.6 no.1
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    • pp.44-54
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    • 2004
  • Organic-inorganic composite membranes based on sulfonated poly(phthalazinone ether sulfone) (sPPES)/silica hybrid were prepared using the sol-gel process under acidic conditions. The sulfonation of PPES with concentrated sulfuric acid as sulfonation agent was carried out to prepare proton exchange membrane material. The behaviors of the proton conductivity and methanol permeability are depended on the sulfonation time (5-100 hr). The hybrid membranes composed of highly sulfonated PPES (IEC value: 1.42 meq./g) and silica were fabricated from different silica content (5-20 wt%) in order to achieve desirable proton conductivity and methanol permeability demanded for fuel cell applications. The silica particles within membranes were used for the purpose of blocking excessive methanol cross-over and for forming the path way to transport of the proton due to absorbing water molecules with ≡SiOH on silica. The presence of silica particles in the organic polymer matrix results in hybrid membranes with reduced methanol permeability and improved proton conductivity.

Characterization of Polymer Blends of Poly(ether sulfone)/Sulfonated Poly(ether ether ketone) for DMFC (직접메탄올 연료전지용 Poly(ether sulfone)/Sulfonated Poly(ether ether ketone) 블렌드 막의 특성 연구)

  • Cheon, Hun Sang;Lee, Choong Gon;Hong, Seong Uk
    • Applied Chemistry for Engineering
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    • v.16 no.1
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    • pp.144-149
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    • 2005
  • Sulfonated poly(ether ether ketone) (SPEEK) was blended with poly(ether sulfone) (PES) at various compositions. To investigate the possibility of using the blend membranes as polymer electrolyte membranes for direct methanol fuel cell, the blend membranes were characterized in terms of methanol permeability, proton conductivity, ion exchange capacity, and water content. Both proton conductivity and methanol permeability of SPEEK were relatively high. As the amount of PES increased, methanol permeability decreased more rapidly compared to proton conductivity. The experimental results indicated that the blend membrane with 40 wt% PES was the best choice in terms of the ratio of proton conductivity to methanol permeability.

Effects of Water on the Electrical Conductivity of Magnesium Metaphosphate Glasses (MgO.$P_2O_5$ 유리의 전기전도도에 미치는 수분의 영향)

  • 강은태;박용완
    • Journal of the Korean Ceramic Society
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    • v.23 no.4
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    • pp.85-89
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    • 1986
  • Electrical conductivity have been measured as function of temperature in MgO.$P_2O_5$ glasses containing small amounts of water. Conduction was due to the contribution of $H^+$ and the mobility of protons in the glass increased linearly with increasing its concentration. The conductivity was pro-portional to the square of the proton concentration and the activation energy decreased linerly with increasing logarithm of the proton concentration, And $$\sigma$_0$ and $A_0$ was independent of the proton concentration but not on glass compositions.

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Molecular Structure of Poly(phenylene oxide-g-styrenesulfonic acid) and the Conductivity and Methanol Permeability of the Membrane

  • Cho, Chang-Gi;You, Young-Gyu;Jang, Hye-Young
    • Proceedings of the Polymer Society of Korea Conference
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    • pp.269-269
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    • 2006
  • The molecular structure of poly(2,6-dimethyl-4,4' -phenylene oxide)-g-poly (styrenesulfonic acid) (PPO-g-PSSA) graft copolymer was designed, and synthesized via living radical polymerization. Obtained graft copolymers were transformed into proton exchange membranes for direct methanol fuel cell (DMFC) application. The performance of the membranes was measured in terms of water uptake, proton conductivity, methanol permeability, and thermal stability. Very low methanol permeability and good proton conductivity were observed by adjusting grafting frequency and PSSA block content.

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SPAES/Silicate Hybrid Membranes for High-Temperature and Low-Humidity Proton Exchange Membrane Fuel Cells (고온-저습용 연료전지를 위한 SPAES/Silicate 복합막)

  • So, Soon Yong;Kim, Tae Ho;Kim, Sung Chul;Hong, Young Taik
    • 한국신재생에너지학회:학술대회논문집
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    • pp.147-147
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    • 2010
  • An electrolyte membranes for high temperature/low humidity is a demand for the proton exchange membrane fuel cells (PEMFCs). In this work, we prepared hybrid membranes, which have novel glass content in the hydrophilic and hydrophobic part of sulfonated poly(arylene ether sulfone) (SPAES) by in-situ sol-gel synthesis of various functional silane. The effect of silicate from functional silane content on the proton conductivity, water uptake of the hybrid membranes under high temperature and low humidity was quantitatively identified. The silicate content contributed to the enhancement of not only proton conductivity, but also water retention ability for PEMFCs operation.

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