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The adsorptive abilities of Ni1-xCox-YSZ and Ni1-xCox-CeO2 cermet particles for CH4 and CO were affected by the amount of the Co atoms substituted for the Ni atoms. The CO molecules produced by the partial oxidation of adsorbed CH4 molecules by the O2- ions at the interface between the Ni1-xCox and YSZ (or CeO2) affect the cell performance for the direct oxidation of CH4 in solid oxide fuel cells. The partial substitution of Co for Ni in the fcc lattice increased the amount of the adsorbed species, and decreased the desorption activation energy for CO and CH4.

This paper discusses on the Cr poisoning that occurs in solid oxide fuel cells with metallic alloy separators. The results of a series of experimental, including an analysis of cathodic overvoltage with loading time at a constant current density, observation of the cathode microstructure, and an experiment of chemical compatibility of the cathode material against Cr oxide, are presented. LNF cathodes are more stable against Cr poisoning than LSCF and LSM cathodes. Cr adhesives were observed near the cathode layer for all measured cells in the presence of the alloy. Furthermore, LNF was less reactive with Cr oxide than LSCF and LSM. The results of electrochemical measurements under the Cr poisoning condition agree with that of the chemical properties of the cathode material against Cr oxide.

Ti-doped CeO2 mixed oxide powders (CeO2-TiO2) were synthesized by a sol-gel method with varying amount of Ti. The XRD patterns of CeO2-TiO2 (10 and 20 mol% Ti) powders calcined at 800degC for 4 h did not show the TiO2 phase. The electrical conductivity of CeO2-TiO2 mixed oxide was higher than that of CeO2 between 650 and 750degC under reducing atmosphere. The electrocatalytic activity of Ni/CeO2 and Ni/CeO2-TiO2 cermet anodes were examined under the oxidation of methane for solid oxide fuel cells (SOFCs). The Ni/CeO2-TiO2 (20 mol% Ti) anode showed a higher power density than that Ni/CeO2 in both H2 and CH4 fuels. The enhancement of methane oxidation was most likely to be caused by the higher electrical conductivity of the mixed ionic and electronic CeO2-TiO2 oxide cermet. The electrode polarization of the Ti-doped CeO2 anode was lower than that of the non-doped CeO2 anode.

Composites of 3 mol % Y2O3 in ZrO2, Ce0.9Gd0.1O1.95, and Sc0.1Ce0.01Zr0.89O1.95 were mixed with 8 mol % Yttria Stabilized Zirconia (YSZ) in 50:50 weight ratio to compare the influences in mechanical and electrical properties using a 3- point bending test and AC-impedance spectroscopy, respectively. An SEM was used for a morphological analysis and an XRD was used to identify phases. The composite of 3YSZ+8YSZ has shown a mixed phase between small and large grains referring to the cubic and tetragonal phases. From AC-impedance measurements, the composite of 8YSZ+ScSZ shows the maximum bulk and grain boundaries conductivities. The mechanical strength of 8YSZ has been proved to increase tremendously when mixed with the tetragonal phase of 3YSZ. However, The maximum bending strength is obtained from 8YSZ+ScSZ composite after sintering for 4 hours. The results have shown very positive solution using a composite of 8YSZ+ScSZ for the intermediate temperature electrolyte for SOFCs.

Polarization resistance of the LaNi0.6Fe0.4O3 (LNF) cathode has been investigated in relation to the electrical conductivity and thermochemical stability. Electrochemical properties of a solid oxide fuel cell using LNF as the cathode were compared to those using La0.8Sr0.2MnO3 (LSM). Temperature dependence of the cathodic polarization resistance was discussed in terms of the thermochemical stability. The electrical conductivity of bulk LNF sample was measured with the four-probe DC method at different oxygen partial pressures. Phase identification for the LNF powder samples treated at 900oC in the atmosphere of oxygen and argon was studied with time dependency of heat treatment by X- ray diffraction analysis. Although the rhombohedral crystal structure of the starting phase was maintained, the electrical conductivity of LNF sensitively changed with the partial pressure of oxygen.

Partial substitution of Co atoms for Ni atoms in the Ni-based cermet anode resulted in a decrease in the anodic overvoltage and interfacial resistance between the anode and electrolyte. This effect has been confirmed for yttria-stabilized zirconia (YSZ) and scandia-stabilized zirconia (ScSZ) electrolytes. The Ni1-XCoX-ScSZ (-YSZ) cermet anode showed an increase in the cell performance with increasing amount of Co content up to approximately 0.5. The decrease in the anodic overvoltage and the interfacial resistance contributes to an enhancement of the cell performance. The results of electrochemical measurements and microstructural characterization revealed that the enhancement of the direct oxidation of methane is caused by the modification of microstructure due to a solid- solutioning effect in the starting NiO-CoO binary system.

This paper discusses on the Cr poisoning that occurs in solid oxide fuel cells with metallic alloy separators. The results of a series of experimental, including an analysis of cathodic overvoltage with loading time at a constant current density, observation of the cathode microstructure, and an experiment of chemical compatibility of the cathode material against Cr oxide, are presented. LNF cathodes are more stable against Cr poisoning than LSCF and LSM cathodes. Cr adhesives were observed near the cathode layer for all measured cells in the presence of the alloy. Furthermore, LNF was less reactive with Cr oxide than LSCF and LSM. The results of electrochemical measurements under the Cr poisoning condition agree with that of the chemical properties of the cathode material against Cr oxide.