• The Korean Journal of Ceramics
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• v.4 no.2
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• pp.136-140
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• 1998

This work demonstrates a method for modeling of electrical conductivity in high-temperature proton-conducting oxides. Total conductivity was calculated assuming that it comprises partial conductivities contributed by protons, oxygen ions and electron holes. From the polt $\sigma_{tot}$ vs. $po_2\;{1/4}$ in wet atmosphere, thermodynamic and kinetic parameters were obtained representing transport properties such as concentration and mobility of the charge-carrying defects. The formulas for the calculation of partial conduction were derived based on the defect structure of HTPCs. Illustrative calculation were made for $SrCe_{0.95}Yb_{0.05}O_{2.975}$ system.

• Macromolecular Research
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• v.14 no.4
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• pp.438-442
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• 2006

Novel sulfonated poly(aryl ether ketones) containing benzoxazole were directly synthesized by aromatic nucleophilic polycondensation using various ratios of 2,2'-bi[2-( 4-flurophenyl)benzoxazol-6-yl]hexafluoropropane to sodium 5,5'-carbonylbis(2-fluorobenzenesulfonate). The copolymers were soluble in polar aprotic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide at a relatively high solid composition (>15 wt%) and formed tough, flexible and transparent membranes. The membranes exhibited a degradation temperature of above $290^{\circ}C$. The exact dissolution times of these membranes at $80^{\circ}C$ in Fenton's reagent (3 wt% $H_2O_2$ containing 2 ppm $FeSO_4$) were undetectable, confirming their excellent chemical stability in fuel cell application. The membranes showed a moderate increase in water uptake with respect to increasing temperature. The proton conductivities of the membranes were dependent on the composition and ranged from $1.10{\times}10^{-2}$ to $5.50{\times}10^{-2}Scm^{-1}$ at $80^{\circ}C$ and 95% relative humidity (RH). At $120^{\circ}C$ without externally humidified conditions, the conductivities increased above $10^{-2}Scm^{-1}$ with respect to increasing benzoxazole content, which suggested that the benzoxazole moieties contributed to the proton conduction.

• Membrane Journal
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• v.23 no.4
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• pp.290-296
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• 2013

Poly(vinylidenefluoride-co-chlorotrifluoroethylene) P(VDF-co-CTFE) polymer was attached to methacrylic acid (MAA) in the presence of 1,8-diazabicyclo[5,4,0]undec-7-ene(DBU) catalyst to prepare P(VDF-co-CTFE)-MAA copolymer. The modified P(VDF-co-CTFE)-MAA was polymerized with 2-sulfoethyl methacrylate (SEMA) monomer in the presence of 4',4'-azobis(4-cyanovaleric acid(ACVA) initiator by free radical polymerization to form the proton conducting membrane. The ratio of the SEMA was increased in the membrane to increase the presence of the acidic group. The maximum IEC value that was observed at 50% SEMA was around 0.82 meq/g, which is consistent with the water uptake value. The highest proton conductivity achieved by P(VDF-co-CTFE)-MAA/SEMA membrane with 50% SEMA was approximately 0.041 S/cm. This indicates that the available ionic group for the proton conduction increases with the increase in the SEMA in the membrane.

• Membrane Journal
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• v.26 no.1
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• pp.1-13
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• 2016

Fuel cells are regarded as a representative energy source expected to replace fossil fuels particularly used in internal combustion engines. One of the most important components is polymer electrolyte membranes (PEMs) acting as a proton conducting barrier to prevent fuel gas crossover. Since water channels act as proton pathways through PEMs, many researchers have been focused on the 'good phase-separation of hydrophilic moiety' which ensures high water retention under low humidity enough to keep the water channel for good proton conduction. Here, we summarized the strategies which have been adopted to synthesize sulfonated PEMs having high proton conductivities even under low humidified conditions, and hope this review will be helpful to design high performance hydrocarbon PEMs.

• Macromolecular Research
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• v.15 no.5
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• pp.412-417
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• 2007

In the present study, crosslinked poly(vinyl alcohol) (PVA) membranes were prepared at different temperatures using poly(styrene sulfonic acid-co-maleic acid) (PSSA_MA) (PVA:PSSA_MA = 1:9). The hybrid mem-branes were prepared by varying the TEOS content between 5 and 30 wt%. The PSSA_MA was used both as a crosslinking agent and the hydrophilic group donor ($-SO_3H$ and/or-COOH). The proton conductivity increased with up to 20 wt% TEOS, but decreased above this level, although the water content decreased with increasing TEOS content. This result suggests that the silica doped into the membrane improved the formation of proton-conduction pathways due to the absorption of molecular water. The PVA/PSSA_MA/Silica containing TEOS 20% showed both high proton conductivity (0.026 S/cm at $90^{\circ}C$) and low methanol permeability ($5.55{\times}10^{-7}cm^2/s$).

• Journal of the Korean Ceramic Society
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• v.36 no.7
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• pp.679-684
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• 1999

Specimens of SrZr0.95Ga0.05O3-$\delta$, SrZr0.95Y0.05O3-$\delta$, BaZr0.95Ga0.05O3-$\delta$ and BaZr0.95Y0.05O3-$\delta$ were fabricated by a solid-state reaction method and subsequent sintering at 150$0^{\circ}C$ to 1$600^{\circ}C$ The microstructures and electrical characteristics of the specimens were studied. Only BaZr0.95Ga0.05O3-$\delta$ showed dense microstructure and had typical impedance spectra at various temperature. Its electrical conductivity by impedance analysis was 2.7$\times$10-3$\Omega$-1.cm-1 at 90$0^{\circ}C$ in air. The BaZr0.95Ga0.05O3-$\delta$ exhibited lower grain rsistance in wet atmosphere than in dry atmosphere and the reduction of resistance is due to the proton conduction.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.218-218
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• 2007

고체 전해질로서 $CsH_2PO_4$결정은 $230^{\circ}C$ 이상에서 전기전도도가 $10^{-2}\;{\Omega}^{-1}cm^{-1}$의 값에 도달하는 초양성자(Superprotonic) 상태로 상전이를 한다. 이러한 이유로 $CsH_2PO_4$ 결정은 $230^{\circ}C$ 부근에서 사용할 수 있는 연료전지로 개발되어왔다. 실용적인 면에서 단결정의 경우보다 다결정의 물성 및 응용 연구가 많았는데, 입자 크기에 따른 체계적인 연구는 잘 이루어지지 않았다. 본 발표에서는 $CsH_2PO_4$ 다결정을 합성하여 SEM 및 micro Raman spectra를 조사하였다. SEM의 결과 입자들의 평균 크기는 100 nm 이었으며, micro Raman spectra는 Bulk $CsH_2PO_4$의 spectra 와 큰 차이를 보이지 않았다. $PO_4$의 내부진동은 거의 같은 주파수대를 보여주나, $300\;cm^{-1}$이하의 저주파 수 영역에서는 광학적 포논의 픽이 잘 보이지 않았다. 그 원인이 micro Raman 장치의 측정 특성인지, 물리적 변화인지는 확실치 않다.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.2
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• pp.128-135
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• 2019

In this study, the mesoporous $SiO_2$ (5, 10, or 15 wt%) was incorporated into the polybenzimidazole matrix in order to improve the proton conduction as well as physiochemical properties of composite membrane. The chemical structure of mesoporous $SiO_2$ and crystallinity of as-prepared membranes were analyzed by Fourier-transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) analysis, respectively. The thermal stability of the pristine $X_1Y_9$ and composite membranes were evaluated by thermogravimetric analyzer (TGA). On other side, the physical and chemical properties of the pristine $X_1Y_9$ and composite membranes were also determined by acid uptake and oxidative stability tests, respectively. With the incorporation of 15 wt% $SiO_2$, the composite membrane exhibits the higher proton conductivity that may be applicable for non-humidified high temperature fuel cell applications.

• Advances in Energy Research
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• v.2 no.2
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• pp.73-84
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• 2014

Fuel cells of proton exchange membrane type (PEMFC) working with hydrogen in the anode and ambient air in the cathode ('air breathing') have been prepared and characterized. The cells have been studied with variable thickness of the cathode catalyst layer ($L_{CL}$), maintaining constant the platinum and ionomer loads. Polarization curves and electrochemical active area measurements have been carried out. The polarization curves are analyzed in terms of a model for a flooded passive air breathing cathode. The analysis shows that $L_{CL}$ affects to electrochemical kinetics and mass transport processes inside the electrode, as reflected by two parameters of the polarization curves: the Tafel slope and the internal resistance. The observed decrease in Tafel slope with decreasing $L_{CL}$ shows improvements in the oxygen reduction kinetics which we attribute to changes in the catalyst layer structure. A decrease in the internal resistance with $L_{CL}$ is attributed to lower protonic resistance of thinner catalyst layers, although the observed decrease is lower than expected probably because the electronic conduction starts to be hindered by more hydrophilic character and thicker ionomer film.

• Journal of the Korean Magnetic Resonance Society
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• v.18 no.1
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• pp.41-46
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• 2014

In order to obtain information on the structural geometry of $NH_4HSeO_4$ near the phase transition temperature, the spectrum and spin-lattice relaxation time in the rotating frame $T_{1{\rho}}$ for the ammonium and hydrogen-bond protons were investigated through $^1H$ MAS NMR. $T_{1{\rho}}$ for the hydrogen-bond protons abruptly decreased at high temperature and it is associated with the change in the structural geometry in $O-H{\cdots}O$ bonds. This mobility of the hydrogen-bond protons may be the main reason for the high conductivity.