Brian D. Madsen

A Fuel-Flexible Ceramic-Based Anode for Solid Oxide Fuel Cells

Results are presented on a solid oxide fuel cell (SOFC) anode material designed for use with C-containing fuels: a composite of an electronically conducting ceramic, La 0 . 8 Sr 0 . 2 Cr 0 . 8 Mn 0 . 2 O 3 - Φ , an ionically conducting ceramic, Ce 0 . 9 Gd 0 . 1 O 1 . 9 5 (GDC), and a small fraction Ni. These ceramic-based anodes were tested in SOFCs with GDC bulk electrolytes. The anode performance was comparable to that for Ni-GDC anodes with hydrogen and methane fuels. The anodes also provided good performance with propane and butane and, unlike Ni-GDC, there was little or no coking. The 4 wt % Ni content in the anode was necessary to obtain good performance, indicating that a small amount of Ni provides a substantial electrocatalytic effect while not causing coking. Initial cell test results showed good cell stability and indicated that the anodes were not affected by cyclic oxidation and reduction.

Nickel- and Ruthenium-Doped Lanthanum Chromite Anodes: Effects of Nanoscale Metal Precipitation on Solid Oxide Fuel Cell Performance

This paper compares the effects of Ni and Ru dopants in lanthanum chromite anodes by correlating structural characterization and electrochemical measurements in solid oxide fuel cells (SOFCs). Transmission electron microscope observations showed that nanoclusters of Ni or Ru metal precipitated onto lanthanum chromite (La 0.8 Sr 0.2 Cr 1-y X y O 3-δ , X = Ni,Ru) surfaces, respectively, after exposure to hydrogen at 750-800°C. Ni nanoclusters were typically ∼10 nm in diameter immediately after reduction and coarsened to ~50 nm over ~300 h at 800°C. In contrast, Ru cluster size was stable at ≤5 nm, and the cluster density was > 10 times larger. SOFC tests were done with the doped lanthanum chromite anodes on La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-δ electrolyte-supported cells. Ni nanocluster nucleation improved cell performance and reduced anode polarization resistance compared to cells with undoped (La 0.8 Sr 0.2 CrO 3-δ ) anodes, but the improvement was much less than that for Ru. This comparison suggests that the smaller size of the Ru nanoclusters played an important role in enhancing anode electrochemical kinetics.

Application of LaSr2Fe2CrO9-δ in solid oxide fuel cell anodes

The oxide composition LaSr 2 Fe 2 CrO 9-δ was tested for application as an anode material for solid oxide fuel cells. Despite the high Fe content, this composition was found to be stable under SOFC anode conditions up to ∼800°C. The composite anode LaSr 2 Fe 2 CrO 9-δ -Gd 0.1 Ce 0.9 O 2-δ was tested in Gd 0.1 Ce 0.9 O 2-δ and La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-δ electrolyte-supported cells in air and humidified H 2 . The maximum power density was ≈365 mW/cm 2 at 800°C, with a corresponding total cell resistance of ≈0.69 Ω cm 2 . However, the anode polarization resistance at 800°C was ≈0.25 Ω cm 2 .

Electron Microscopy Study of Novel Ru Doped La0.8Sr0.2CrO3 as Anode Materials for Solid Oxide Fuel Cells (SOFCs)

Solid Oxide Fuel Cells (SOFCs) have been the center of research activities with the goal of improving energy efficiency and reducing air pollution. There has been great interest in incorporating nanostructures into SOFCs to yield improved electrolyte and electrode performance [1,2]. For instance, small amounts of electrocatalyst nanoparticles have been introduced into ceramic anodes to improve the electrochemical characteristics. However, these nanoparticles are prone to coarsening at the fairly high firing temperature used during fabrication. In this study, a new method was shown to produce metal nanoparticles on anode surfaces after these high temperature processing. Electron microscopy study was carried out to characterize the new anode materials.

La0.8Sr0.2Cr0.98V0.02O3 − δ Ce0.9Gd0.1O1.95 – Ni Anodes for Solid Oxide Fuel Cells Effect of Microstructure and Ni Content

Solid oxide fuel cells (SOFCs) were fabricated with thick Ce0.9Gd0.1O1.95 (GDC) electrolytes, composite anodes containing La0.8Sr0.2Cr0.98V0.02O3-delta (LSCV), GDC, and NiO, and Au current collector grids. SOFCs with varying anode firing temperatures, GDC contents, and NiO contents were structurally evaluated and characterized by current-voltage measurements and electrochemical impedance spectroscopy in humidified hydrogen and air. With increasing anode firing temperature, particle sizes in the porous anodes increased and the area specific resistance (R-AS) increased (power density decreased). For lower firing temperatures, e.g., 1100 degrees C, R-AS decreased sharply with increasing NiO content from 0 to 5 wt %, but showed little further decrease from 5 to 20 wt % NiO. R-AS values were generally higher for higher firing temperatures, e.g., 1400 degrees C, decreasing gradually with increasing NiO content from 0 to 20 wt %. These trends were explained by an increase in Ni particle sizes with increasing firing temperature, making the Ni catalyst less effective. The anode polarization resistance at 750 degrees C was similar to 0.8 Omega cm(2) at 450 mV cell voltage (0.1 Omega cm(2) at open circuit), for a composition of 47.5 wt % LSCV, 47.5 wt % GDC, and 5 wt % NiO. (c) 2007 The Electrochemical Society.

La[sub 0.8]Sr[sub 0.2]Cr[sub 0.98]V[sub 0.02]O[sub 3−δ]Ce[sub 0.9]Gd[sub 0.1]O[sub 1.95]–Ni Anodes for Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) were fabricated with thick Ce0.9Gd0.1O1.95 (GDC) electrolytes, composite anodes containing La0.8Sr0.2Cr0.98V0.02O3-delta (LSCV), GDC, and NiO, and Au current collector grids. SOFCs with varying anode firing temperatures, GDC contents, and NiO contents were structurally evaluated and characterized by current-voltage measurements and electrochemical impedance spectroscopy in humidified hydrogen and air. With increasing anode firing temperature, particle sizes in the porous anodes increased and the area specific resistance (R-AS) increased (power density decreased). For lower firing temperatures, e.g., 1100 degrees C, R-AS decreased sharply with increasing NiO content from 0 to 5 wt %, but showed little further decrease from 5 to 20 wt % NiO. R-AS values were generally higher for higher firing temperatures, e.g., 1400 degrees C, decreasing gradually with increasing NiO content from 0 to 20 wt %. These trends were explained by an increase in Ni particle sizes with increasing firing temperature, making the Ni catalyst less effective. The anode polarization resistance at 750 degrees C was similar to 0.8 Omega cm(2) at 450 mV cell voltage (0.1 Omega cm(2) at open circuit), for a composition of 47.5 wt % LSCV, 47.5 wt % GDC, and 5 wt % NiO. (c) 2007 The Electrochemical Society.

La0.8 Sr0.2 Cr0.98 V0.02 O3-δ Ce0.9 Gd0.1 O1.95 -Ni anodes for solid oxide fuel cells

Solid oxide fuel cells (SOFCs) were fabricated with thick Ce0.9Gd0.1O1.95 (GDC) electrolytes, composite anodes containing La0.8Sr0.2Cr0.98V0.02O3-delta (LSCV), GDC, and NiO, and Au current collector grids. SOFCs with varying anode firing temperatures, GDC contents, and NiO contents were structurally evaluated and characterized by current-voltage measurements and electrochemical impedance spectroscopy in humidified hydrogen and air. With increasing anode firing temperature, particle sizes in the porous anodes increased and the area specific resistance (R-AS) increased (power density decreased). For lower firing temperatures, e.g., 1100 degrees C, R-AS decreased sharply with increasing NiO content from 0 to 5 wt %, but showed little further decrease from 5 to 20 wt % NiO. R-AS values were generally higher for higher firing temperatures, e.g., 1400 degrees C, decreasing gradually with increasing NiO content from 0 to 20 wt %. These trends were explained by an increase in Ni particle sizes with increasing firing temperature, making the Ni catalyst less effective. The anode polarization resistance at 750 degrees C was similar to 0.8 Omega cm(2) at 450 mV cell voltage (0.1 Omega cm(2) at open circuit), for a composition of 47.5 wt % LSCV, 47.5 wt % GDC, and 5 wt % NiO. (c) 2007 The Electrochemical Society.