Characterization of ceria-based SOFCs

Solid Oxide Fuel Cells (SOFCs) operating at low temperatures (500-700 C) offer many advantages over conventional zirconia-based fuel cells operating at higher temperatures. Cathode performance is being improved by using better materials and/or microstructures. Fabrication of thin dense electrolytes is also necessary to achieve high cell performances

The low-temperature partial-oxidation reforming of fuels for transportation fuel cell systems

Argonne`s partial-oxidation reformer (APOR) is a compact, lightweight, rapid-start, and dynamically responsive device to convert liquid fuels to H{sub 2} for use in automotive fuel cells. An APOR catalyst for methanol has been developed and tested; catalysts for other fuels are being evaluated. Simple in design, operation, and control, the APOR can help develop efficient fuel cell propulsion systems

Partial oxidation reforming of methanol

Methanol is an attractive fuel for fuel cell-powered vehicles because it has a fairly high energy density, can be pumped into the tank of a vehicle mush like gasoline, and is relatively easy to reform. For on-board reforming, the reformer must be compact and lightweight, and have rapid start-up and good dynamic response. Steam reforming reactors with the tube-and-shell geometry that was used on the prototype fuel cell-powered buses are heat transfer limited. To reach their normal operating temperature, these types of reactors need 45 minutes from ambient temperature start-up. The dynamic response is poor due to temperature control problems. To overcome the limitations of steam reforming, ANL explored the partial oxidation concept used in the petroleum industry to process crude oils. In contrast to the endothermic steam reforming reaction, partial oxidations is exothermic. Fuel and air are passed together over a catalyst or reacted thermally, yielding a hydrogen-rich gas. Since the operating temperature of such a reactor can be controlled by the oxygen-to- methanol ratio, the rates of reaction are not heat transfer limited. Start-up and transient response should be rapid, and the mass and volume are expected to be small by comparison

Non-segregating electrolytes for molten carbonate fuel cells

Current MCFCs use a Li/K carbonate mixture; the segregation increases the K concentration near the cathode, leading to increase cathode solubility and performance decline. ANL is developing molten carbonates that have minimal segregation; the approach is using Li-Na carbonates. In screening tests, fully developed potential distributions were obtained for 4 Li/Na compositions, and performance data were used to compare these

Microengineered cathode interface studies

The overpotential at the cathode/electrolyte interface has been recognized as an important limitation on the performance of solid oxide fuel cells (SOFCs). This project is an effort to gain a scientific understanding of which interface features and conditions contribute to cathode polarization in SOFCs. The paper discusses three possible rate-limiting factors in the cathode reaction. The paper studies the electronic conductivity in the electrolyte, the ionic conductivity in the cathode, cathode geometry near the interface, and cathode surface area

The low-temperature partial oxidation reforming of fuels for transportation fuel cell systems

Argonne`s partial-oxidation reformer (APOR) is a compact, lightweight, rapid-start, and dynamically responsive device to convert liquid fuels to H{sub 2} for use in automotive fuel cells. An APOR catalyst for methanol has been developed and tested; catalysts for other fuels are being evaluated. Simple in design, operation, and control, the APOR can help develop efficient fuel cell propulsion systems

Characterization of ceria-based SOFCs

Solid Oxide Fuel Cells (SOFCs) operating at low temperatures (500-700 C) offer many advantages over conventional zirconia-based fuel cells operating at higher temperatures. Cathode performance is being improved by using better materials and/or microstructures. Fabrication of thin dense electrolytes is also necessary to achieve high cell performances

Progress in carbonate fuel cells

Our objective is to increase both the life and power of the molten carbonate fuel (MCFC) by developing improved components and designs. Current activities are as follows: (1)Development of LiFeO{sub 2} and LiCoO{sub 2} cathodes for extended MCFC life, particularly in pressurized operation, where the present cathode, NiO, provides insufficient life (2) Development of distributed-manifold MCFC designs for increased volumetric power density and decreased temperature gradients (and, therefore, increased life) (3) Development of components and designs appropriate for high-power density operation (>2 kW/m{sup 2}and >100 kW/m{sup 3}in an integrated MCFC system) (4)Studies of pitting corrosion of the stainless-steel interconnects and aluminized seals now being employed in the MCFC (alternative components will also be studied). Each of these activities has the potential to reduce the MCFC system cost significantly. Progress in each activity will be presented during the poster session

Cathodes for ceria-based fuel cells

Work is underway to develop a solid oxide fuel cell that has a ceria-based electrolyte and operates at lower temperatures (500-600{degrees}C) than conventional zirconia-based cells. At present the performance of this ceria-based solid oxide fuel cell is limited by the polarization of conventional cathode materials. The performance of alternative cathodes was measured by impedance spectroscopy and dc polarization. The performance was found to improve by using a thin dense interface layer and by using two-phase cathodes with an electrolyte and an electronic phase. The cathode performance was also found to increase with increasing ionic conductivity for single phase cathodes

Alternative cathodes for molten carbonate fuel cells

Argonne National Laboratory (ANL) is developing advanced cathodes for pressurized operation of the molten carbonate fuel cell (MCFC). The present cathode, lithiated nickel oxide, tends to transport to the anode of the MCFC, where it is deposited as metallic nickel. The rate of transport increases with increasing CO{sub 2} pressure. This increase is due to an increased solubility of nickel oxide (NiO) in the molten carbonate electrolyte. An alternative cathode is lithium cobaltate (LiCoO{sub 2})-Solid solutions of LiCoO{sub 2} in LiFeO{sub 2} show promise for long-lived cathode materials. We have found that small additions of LiCoO{sub 2} to LiFeO{sub 2} markedly decrease the resistivity of the cathode material. Cells containing the LiCoO{sub 2}-LiFeO{sub 2} cathodes have stable performance for more than 2100 h of operation and display lower cobalt migration