Porous yttria-stabilized zirconia ͑YSZ͒ was impregnated with aqueous solutions of the nitrate salts of Sr, La, and Co to obtain composites of La 0.6 Sr 0.4 CoO 3Ϫ␦ ͑LSCo͒ and YSZ. X-ray diffraction showed that the perovskite phase formed after heating to 973 K and conductivities as high as 7 S/cm were achieved at 973 K with only 30 wt % LSCo. Coefficient of thermal expansion ͑CTE͒ measurements of the composites with as much as 50 wt % LSCo indicated that the CTEs were much lower than the weighted average of the YSZ and LSCo. Electrochemical measurements using symmetric cells in air indicated that the area-specific resistance ͑ASR͒ of the composites could be as low as 0.03 ⍀ cm 2 at 973 K and 0.01 ⍀ cm 2 at 1073 K. These low ASR were verified in a cell with an LSCo-YSZ cathode and a Co-ceria-YSZ anode, which exhibited a total electrode polarization loss of 0.25 ⍀ cm 2 at 973 K and 0.1 ⍀ cm 2 at 1073 K for operation in humidified H 2 . However, changes in electrochemical performance with time showed that some electrode degradation occurred over a period of 250 h, even at 973 K.

In this study, we report on how different impregnation procedures affect the distribution and morphology of the Cu component in Cu/CeO 2 /YSZ composite anodes and how this affects anode performance. Two different methods for Cu addition to the porous YSZ anode were investigated: impregnation using aqueous solutions of Cu(NO 3 ) 2 and impregnation using aqueous solutions of Cu(NO 3 ) 2 plus urea. The latter method produced a homogeneous distribution of Cu throughout the anode while the former resulted in a higher concentration of Cu near the exposed surface relative to that in the bulk. Studies of the thermal stability of the deposited copper layers, and the influence of the Cu distribution on cell performance when operating with humidified H 2 as the fuel are also presented. AbstractIn this study we report on how different impregnation procedures affect the distribution and morphology of the Cu component in Cu/CeO 2 /YSZ composite anodes and how this affects anode performance. Two different methods for Cu addition to the porous YSZ anode were investigated: impregnation using aqueous solutions of Cu(NO 3 ) 2 and impregnation using aqueous solutions of Cu(NO 3 ) 2 plus urea. The latter method produced a homogeneous distribution of Cu throughout the anode while the former resulted in a higher concentration of Cu near the exposed surface relative to that in the bulk. Studies of the thermal stability of the deposited copper layers, and the influence of the Cu distribution on cell performance when operating with humidified H 2 as the fuel are also presented.

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The performance and stability of Cu-ceria-YSZ (yttria-stabilized zirconia) and carbon-ceria-YSZ, solid-oxidefuel-cell (SOFC) anodes were examined in neat (100%) methanol at 973K and compared to the performance of the same anodes in dry H 2 . The presence of Cu catalyzed the decomposition of methanol, so that the initial performance of cells with Cu-ceria-YSZ anodes was similar to CO and H 2 . However, with carbon-ceria-YSZ anodes, the open-circuit voltage was significantly higher and the reaction over-potential significantly lower in methanol than in H 2 , suggesting that methanol is a more effective reductant of the anode three-phase boundary region. Carbon-ceria-YSZ anodes were found to undergo rapid and irreversible deactivation in methanol. Steady-state rates of methanol decomposition over ceria-YSZ were found to undergo a similar deactivation as the carbon-ceria anodes. Although no evidence for carbon deposition was observed with methanol at 973 K, the addition of steam was found to partially stabilize both anode and catalyst performance. Scanning electron microscopy (SEM) of ceria particles in YSZ showed a large change in the morphology of the ceria particles when the samples were heated in methanol, while negligible changes were observed when heating in H 2 . It is suggested that the results with methanol can be explained as resulting from the very low P(O 2 ) that is effectively produced by having methanol in contact with ceria. AbstractThe performance and stability of Cu-ceria-YSZ (yttria-stabilized zirconia) and carbonceria-YSZ, solid-oxide-fuel-cell (SOFC) anodes were examined in neat (100%) methanol at 973K and compared to the performance of the same anodes in dry H 2 . The presence of Cu catalyzed the decomposition of methanol, so that the initial performance of cells with Cu-ceria-YSZ anodes was similar for methanol and H 2 . However, with carbon-ceria-YSZ anodes, the opencircuit voltage was significantly higher and the reaction over-potential significantly lower in methanol than in H 2 , suggesting that methanol is a more effective reductant of the anode threephase boundary region. Carbon-ceria-YSZ anodes were found to undergo rapid and irreversible deactivation in methanol. Steady-state rates of methanol decomposition over ceria-YSZ were found to exhibit a similar deactivation the carbon-ceria anodes. Although no evidence for carbon deposition was observed with methanol at 973 K, the addition of steam was found to partially stabilize both anode and catalyst performance. SEM of ceria particles in YSZ showed a large change in the morphology of the ceria particles when the samples were heated in methanol, while negligible changes were observed when heating in H 2 . It is suggested that the results with methanol can be explained as resulting from the very low P(O 2 ) that is effectively produced by having methanol in contact with ceria.