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

Abstract

The properties of solid oxide fuel cell ͑SOFC͒ anode functional layers prepared by impregnation of ceria and catalytic metals into porous yttria-stabilized zirconia ͑YSZ͒ have been examined for operation at 973 K. By varying the thickness of the functional layer, the conductivity of the ceria-YSZ composite was determined to be only 0.015-0.02 S/cm. The initial performance of anodes made with ceria loadings of 40 or 60 wt % were similar but the anodes with lower loadings lost conductivity above 1073 K due to sintering of the ceria. The addition of dopant levels of catalytic metals was found to be critical. The addition of 1 wt % Pd or Ni decreased the anode impedances in humidified H 2 dramatically, while the improvement with 5 wt % Cu was significant but more modest. Pd doping also decreased the anode impedance in dry CH 4 much more than did Cu doping; however, addition of either Pd or Cu led to similar improvements for operation in n-butane. Based on these results, suggestions are made for ways to improve SOFC anode functional layers.

Insights into the Design of SOFC Infiltrated Electrodes with Optimized Active TPB Density via Mechanistic Modeling

“…Our results are consistent with previous infiltrated electrode experimental work, which has reported the conductivity of infiltrated electrodes to be approximately 2% to 5% of the bulk conductivity. 5,6,16,22 …”

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

“…100 μm) non-catalytic conduction layer formed by a porous mixed-conductor material, specifically strontium-doped lanthanum titanate (La 0.3 Sr 0.7 TiO 3 , LST). This type of anode gave excellent performance both in H 2 and hydrocarbon fuels and took advantage of the high activity of Pd/ceria for the oxidation of hydrocarbons [147] and of the thermal stability of LST. A similar concept has been used in another study [148] with a Ni/YSZ active layer.…”

“…That is, anodes that do not catalyze carbon formation tend to be less active for the electrochemical oxidation reaction. The combination of relatively thin functional layers that are highly active electrochemically with thicker conduction layers that reform the fuel without carbon formation [146][147][148] is a very attractive approach.…”

Analysis of the performance of the electrodes in a natural gas assisted steam electrolysis cell

“…Our group has developed alternative electrode designs that circumvent this problem by either replacing Ni with Cu which is not prone to coking [Gorte et al, 2000;Kim et al,. 2001;Lu et al, 2003] or using all ceramic electrode formulations [Gross et al, 2007;Gross et al, 2007]. For example, we have shown that electrodes based on thin porous YSZ layers that are impregnated with high loadings of CeO 2 (40 wt %) and dopant levels of a catalytically active metal such as Pd exhibit excellent performance on both H 2 and CH 4 in SOFCs [Gross et al, 2007;Gross et al, 2007].…”

“…2001;Lu et al, 2003] or using all ceramic electrode formulations [Gross et al, 2007;Gross et al, 2007]. For example, we have shown that electrodes based on thin porous YSZ layers that are impregnated with high loadings of CeO 2 (40 wt %) and dopant levels of a catalytically active metal such as Pd exhibit excellent performance on both H 2 and CH 4 in SOFCs [Gross et al, 2007;Gross et al, 2007]. One of the objectives of the work presented here was to evaluate the performance of electrodes of this design in an NGASE cell.…”