Papers by Keyword: Intermediate Temperature

Abstract: The (ZrO₂-1.6P₂O₅)-PTFE composite electrolytes have been prepared by mixing PTFE powders with different particle sizes and the shell-core-type ZrO₂-1.6P₂O₅ electrolyte, synthesized by solid state reaction with diammonium hydrogen phosphate, to improve the mechanical strength of the electrolyte. The H₂ gas permeability decreased and the cell performances improved with decreasing PTFE-particle size. The aging at 0.4 V above 443 K enhanced the ITFC performance owing to the penetration of the electrolyte to the carbon paper. The maximum output power enhanced by 63% after 15 h of aging at 573 K.

Abstract: Proton conducting ZrO2－yP2O5 (y = 1.0, 1.2, 1.4. 1.6, 1.8) electrolytes based on a shell-core structure were synthesized with diammonium hydrogen phosphate by a solid state reaction, and their conductivities were investigated by ac-impedance spectroscopy. Among the ZrO2-yP2O5 compositions, ZrO2－1.6P2O5 showed the highest proton conductivity of 0.13 Scm-1 at 250°C. The conductivity increased with increasing P2O5 molar ratio and were significantly influenced by heat-treatments in the preparation process. Polytetraflouroethylene (PTFE) was also mixed into these electrolytes in order to improve the mechanical strength and long term durability.

Abstract: The ternary oxide compositions xZrO2-(0.5–x/2)Al2O3-yP2O5(x=0.8, 0.9, 0.95, 1.0; y=1.0, 1.2, 1.4) and 0.9ZrO2-0.05In2O3-1.4P2O5, xSiO2-(0.5–x/2)Al2O3-1.4P2O5(x=0.9, 1.0) were synthesized by sol-gel methods, and their conductivities were investigated by ac-impedance spectroscopy. The conductivity increased with increasing P2O5 content and with decreasing heat-treatment temperature. The maximum conductivities reached over 10-2 Scm-1 at 150°C for 0.9ZrO2-0.05Al2O3-1.4P2O5 and at 225°C for 0.9SiO2-0.05Al2O3-1.4P2O5.

Abstract: For intermediate temperature operation, we chose an anode-supported, planar type SOFC (Solid Oxide Fuel Cell) design considering mass production with use ferritic stainless steels as cost-effective interconnects. Anode-supported single cells with thin electrolyte layer of YSZ(Yttria-Stabilized Zirconia) were fabricated and short stacks were built and evaluated. We also developed diesel and methane autothermal reforming(ATR) reactors in order to provide fuels to SOFC stacks. Influences of the H2O/C(steam to carbon ratio), O2/C(oxygen to carbon ratio) and GHSV(Gas Hourly Space Velocity) on performances of stacks have been investigated. Performance of the stack operated with a diesel reformer was lower than with using hydrogen as a fuel due to lower Nernst voltage and carbon formation at anode side. The stack operated with a natural gas reformer showed similar performances as with using hydrogen. Effects of various reformer parameters such as H2O/C and O2/C were carefully investigated. We found O2/C is a sensitive parameter to control stack performance.