Structure and thermal stability of ceria films supported on YSZ(100) and α-Al2O3(0001)

Costa-Nunes, Olga; Ferrizz, Robert Matthew; Gorte, Raymond J.; Vohs, John M.

doi:10.1016/j.susc.2005.06.029

Cited by 25 publications

(20 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The second surprise is the large change in ceria morphology that occurs upon treatment of ceria at a temperature of only 973 K. That macroscopic movement of ceria in contact with YSZ can occur following oxidation and reduction has already been demonstrated with ceria films on YSZ single crystals [28,29], but this movement has not previously been reported to affect fuel-cell properties. Furthermore, the previous work with ceria films on YSZ found that reduction caused ceria to "spread" over the YSZ surface, the opposite of what appears to be occurring to ceria upon methanol exposure in the fuel cell.…”

Section: Discussionmentioning

confidence: 99%

Deactivation of ceria-based SOFC anodes in methanol

Kim

Ahn

Vohs

et al. 2007

Journal of Power Sources

View full text Add to dashboard Cite

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.

show abstract

Section: Discussionmentioning

confidence: 99%

Deactivation of ceria-based SOFC anodes in methanol

Kim

Ahn

Vohs

et al. 2007

Journal of Power Sources

View full text Add to dashboard Cite

show abstract

“…The results further imply that our films are essentially bulk-like in nature, with low strain energy, consistent with the thickness independent lattice constant, and minimal influence of low-angle tilt boundaries present in the growth direction, consistent with the narrow FWHM measured in the rocking curve diffraction experiment. In contrast, in very thin films, 10 nm or less, 37 and in nanostructured bulk materials 38 , where K 00 directly yields the standard Gibb's free energy of cerium reduction. …”

Section: à2mentioning

confidence: 99%

Electrochemical studies of capacitance in cerium oxide thin films and its relationship to anionic and electronic defect densities

Chueh

Haile

2009

Phys. Chem. Chem. Phys.

100

130

View full text Add to dashboard Cite

“…The LA support was chosen because of its high surface area and excellent thermal stability under redox conditions. Also, we anticipated that interactions between ceria and LA would have a negligible effect on the reducibility of ceria, in contrast to the strong promotion of ceria reduction observed with ceria on zirconia [35,41]. Unlike pure ceria, the ceria/LA samples were found to be quite stable to redox cycling.…”

Section: High-surface-area Ceria and Ceria/lamentioning

confidence: 99%

“…To minimize formation of ceria aluminates [35] and maintain surface area following hightemperature treatment, the alumina was doped with 11.5-wt% La 2 O 3 . The effect of rare-earth dopants was also studied on bulk samples doped with Y +3 and Sm +3 .…”

Section: Introductionmentioning

confidence: 99%

Oxidation enthalpies for reduction of ceria surfaces

et al. 2007

View full text Add to dashboard Cite

The thermodynamic properties of surface ceria were investigated through equilibrium isotherms determined by flow-titration and coulometric-titration measurements on high-surface-area ceria and ceria supported on La-modified alumina (LA). While the surface area of pure ceria was found to be unstable under redox conditions, the extent of reduction at 873 K and a P(O 2 ) of 1.6x10 -26 atm increased with surface area. Because ceria/LA samples were stable, equilibrium isotherms were determined between 873 and 973 K on a 30-wt% ceria sample. Oxidation enthalpies on ceria/LA were found to vary with the extent of reduction, ranging from -500 kJ/mol O 2 at low extents of reduction to near the bulk value of -760 kJ/mol O 2 at higher extents. To determine whether +3 dopants could affect the oxidation enthalpies for ceria, isotherms were measured for Sm +3 -doped ceria (SDC) and Y +3 -doped ceria. These dopants were found to remove the phase transition observed in pure ceria below 973 K but appeared to have minimal effect on the oxidation enthalpies. Implications of these results for catalytic applications of ceria are discussed. AbstractThe thermodynamic properties of surface ceria were investigated through equilibrium isotherms determined by flow-titration and coulometric-titration measurements on high-surfacearea ceria and ceria supported on La-modified alumina (LA). While the surface area of pure ceria was found to be unstable under redox conditions, the extent of reduction at 873 K and a P(O 2 ) of 1.6x10 -26 atm increased with surface area. Because ceria/LA samples were stable, equilibrium isotherms were determined between 873 and 973 K on a 30-wt% ceria sample. Oxidation enthalpies on ceria/LA were found to vary with the extent of reduction, ranging from -500 kJ/mol O 2 at low extents of reduction to near the bulk value of -760 kJ/mol O 2 at higher extents.To determine whether +3 dopants could affect the oxidation enthalpies for ceria, isotherms were measured for Sm +3 -doped ceria (SDC) and Y +3 -doped ceria. These dopants were found to remove the phase transition observed in pure ceria below 973 K but appeared to have minimal effect on the oxidation enthalpies. Implications of these results for catalytic applications of ceria are discussed.

show abstract

Structure and thermal stability of ceria films supported on YSZ(100) and α-Al2O3(0001)

Cited by 25 publications

References 41 publications

Deactivation of ceria-based SOFC anodes in methanol

Deactivation of ceria-based SOFC anodes in methanol

Electrochemical studies of capacitance in cerium oxide thin films and its relationship to anionic and electronic defect densities

Oxidation enthalpies for reduction of ceria surfaces

Contact Info

Product

Resources

About