Deactivation of ceria-based SOFC anodes in methanol

Abstract

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.

An Examination of SOFC Anode Functional Layers Based on Ceria in YSZ

“…Previous studies have reported that ceria films on YSZ have considerable mobility at temperatures similar to that used here, 20 and that this mobility is a strong function of the gas-phase environment. 21 To determine whether or not the increase in ohmic resistance could be attributed to a loss of conductivity in the ceria- YSZ layer, conductivity tests were performed on a YSZ slab, 1 ϫ 1 ϫ 10 mm, impregnated with 40 wt % ceria and 1 wt % Pd, using the standard four-probe method. The slab was made from the same slurry used in making the tapes for the function layers.…”

Direct Utilization of Liquid Fuels in SOFC for Portable Applications: Challenges for the Selection of Alternative Anodes

“…Sammes et al [169] attempted to feed dry MeOH to an SOFC with a lanthanum cobaltite (LaCoO 3 ) anode, but they experienced instability, probably as a consequence of the partial reduction of the perovskite. Jang et al [170] [172] tested Cu/ceria anodes in dry MeOH. They found a significant change of the ceria particles after exposure to MeOH, which was attributed to the agglomeration of ceria particles because of the low oxygen partial pressure created by MeOH.…”

Retraction: High‐Performance Molybdenum Dioxide‐Based Anode for Dodecane‐Fueled Solid‐Oxide Fuel Cells (SOFCs)

“…To address this issue, two major approaches have been considered: using alternative anode materials with a high coking tolerance or co-feeding the fuel with a high concentration of oxidizing agents such as air, CO 2 , or water. [14][15][16][17][18][19] In our previous work we successfully produced a novel MoO 2 -based anode with an exceptionally high coking resistance for liquid hydrocarbons such as n-dodecane and biodiesel at an operating temperature of 850 8C. [20] The procedure developed in our group, which is based on the electrostatic spray deposition (ESD) method, has opened up the possibility of developing liquid hydrocarbon-fueled SOFCs.…”