Supported Solid Oxide Fuel Cells Research Articles

Degradation of Anode Supported SOFCs as a Function of Temperature and Current Load

The degradation behavior of anode supported solid oxide fuel cells (SOFCs) was investigated as a function of operating temperature and current density. Degradation rates were defined and shown to be mainly dependent on the cell polarization. The combination of a detailed evaluation of electrochemical properties by impedance spectroscopy, in particular, and post-test microscopy revealed that cathode degradation was the dominant contribution to degradation at higher current densities and lower temperatures. The anode was found to contribute more to degradation at higher temperatures. Generally, the degradation rates obtained were lower at higher operating temperatures, even at higher current densities. A degradation rate as low as was observed at and over an operating period of .

Properties and Performance of SOFCs Produced on a Pre‐Pilot Plant Scale

AbstractIn the present paper, anode supported solid oxide fuel cells (SOFCs), produced on a pre‐pilot plant scale in ten batches of ∼100 cells, are characterised with respect to performance. The main purpose was to evaluate the reproducibility of the scaled‐up process. Based on 20 tests, the average area specific cell resistance at 850 °C was found to be 0.24 Ω cm2 with a standard deviation of 0.05 Ω cm2. The variation in performance between the cells can be largely attributed to variations in the cathode performance. Experimental evidence will be presented on full 4 × 4 cm2 cells, symmetric cells with two cathodes on a YSZ strip, and a special cell with a divided cathode.

Feasibility of Autothermally Reformed Natural Gas on Anode Supported Solid Oxide Fuel Cells

Three different planar anode supported solid oxide fuel cells (SOFC) were tested with hydrogen, with autothermally prereformed natural gas from which sulfur was removed, and with autothermally prereformed natural gas that contained sulfur. The cells were obtained from Forschungszentrum Jülich (FZJ), Energy research Centre of the Netherlands (ECN), and HTceramix SA (HTc). All cells were so called Real-SOFC first generation cells. Cell polarizations were first measured with hydrogen, followed by a 200h test (25A, 800°C) with a selected fuel, and finally cell polarizations were measured with hydrogen. When hydrogen was used as the fuel in the 200h test, the performance for all cells was comparable and no degradation was observed. All cells underwent an initial deactivation process when reformate fuels were used but their cell voltage stabilized during the first 50h. All cells also showed deactivation after the reformate tests when the area specific resistance values were compared to the values obtained from the hydrogen tests. The deactivation was comparable between the sulfur-free and sulfur-rich reformate tests. Sulfur-rich reformate, however, caused oscillation in cell voltages as the sulfur level in natural gas was not constant.

Performance of intermediate temperature (600–800 °C) solid oxide fuel cell based on Sr and Mg doped lanthanum-gallate electrolyte

The solid electrolyte chosen for this investigation was La 0.9Sr 0.1Ga 0.8Mg 0.2O 3 (LSGM). To select appropriate electrode materials from a group of possible candidate materials, AC complex impedance spectroscopy studies were conducted between 600 and 800 °C on symmetrical cells that employed the LSGM electrolyte. Based on the results of the investigation, LSGM electrolyte supported solid oxide fuel cells (SOFCs) were fabricated with La 0.6Sr 0.4Co 0.8Fe 0.2O 3–La 0.9Sr 0.1Ga 0.8Mg 0.2O 3 (LSCF–LSGM) composite cathode and nickel–Ce 0.6La 0.4O 2 (Ni–LDC) composite anode having a barrier layer of Ce 0.6La 0.4O 2 (LDC) between the LSGM electrolyte and the Ni–LDC anode. Electrical performances of these cells were determined and the electrode polarization behavior as a function of cell current was modeled between 600 and 800 °C.

Effect of Operational Conditions on Long-Term Stability of SOFCs

The long-term stability of anode supported solid oxide fuel cells (SOFCs) was investigated as a function of operating temperature and current density. The largest degradation rate was observed at the lower operating temperature and higher current density of 750°C and 0.75 A/cm 2 , respectively. Detailed characterization by impedance spectroscopy and post-test microscopy revealed that cathode degradation is the dominant contribution to the degradation under these conditions. A slight delamination at the cathode/electrolyte interface was observed. At higher operating temperatures, the degradation is generally less severe, even under higher current densities. Degradation rates as low as 2%/1000 h were observed at 850 and 950°C and 1.6 and 1.9 A/cm 2 , respectively, over operating periods of 1500 hours.

Development of lanthanum ferrite SOFC cathodes

A number of studies have been conducted concerning compositional/microstructural modifications of a Sr-doped lanthanum ferrite (LSF) cathode and protective Sm-doped ceria (SDC) layer in an anode supported solid oxide fuel cell (SOFC). Emphasis was placed on achieving enhanced low temperature (700–800 °C) performance, and long-term cell stability. Investigations involved manipulation of the lanthanum ferrite chemistry, addition of noble metal oxygen reduction catalysts, incorporation of active cathode layer compositions containing Co, Fe and higher Sr contents, and attempts to optimize the ceria barrier layer between the LSF cathode and YSZ electrolyte.