Recent worldwide interest in building a decentralized, hydrogen-based energy economy has refocused attention on the solid oxide fuel cell (SOFC) as a potential source of efficient, environmentally friendly, fuel-versatile electric power. Due to its high operating temperature, the SOFC offers several potential advantages over polymer-based fuel cells, including reversible electrode reactions, low internal resistance, high tolerance to typical catalyst poisons, production of high-quality waste heat for (among other uses) reformation of hydrocarbon fuels, as well as the possibility of burning hydrocarbon fuels directly. Today, SOFCs are much closer to commercial reality than they were 20 years ago, due largely to technological advances in electrode material composition, microstructure control, thin-film ceramic fabrication, and stack and system design. These advances have led to dozens of active SOFC development programs in both stationary and mobile power and contributed to commercialization or development in a number of related technologies, including gas sensors,1 solid-state electrolysis devices,2 and iontransport membranes for gas separation and partial oxidation.3 Many reviews are available which summarize the technological advances made in SOFCs over the last 15-35 yearssreaders who are primarily interested in knowing the state-of-the art in materials, design, and fabrication (including the electrodes) are encouraged to consult these reviews.4-12 This review focuses on the factors governing SOFC cathode performancesadvances we have made over † Dedicated to Brian Steele, 1929-2003. Researcher, Entrepreneur, Consensus Seeker. 4791 Chem. Rev. 2004, 104, 4791−4843

Factors Governing Oxygen Reduction in Solid Oxide Fuel Cell Cathodes

Progress in material selection for solid oxide fuel cell technology: A review

The state of the art development of interconnect materials for solid oxide fuel cells (SOFCs) is reviewed. The specific interconnect requirements from a materials design point of view are described in detail. Doped-LaCrO 3 ceramics considered as interconnects for electrolyte-supported planar SOFC suffer from their extreme sensitivity to oxygen partial pressure and high manufacturing cost. Advent of anode-supported planar SOFC allows lower operating temperatures and great efforts have been directed towards the development of metallic interconnects. Chromia formed on the surface of chromium-based alloys are intrinsically too volatile to be viable as interconnects for SOFCs operating above 800 °C. Some intermediate phases occurring between iron-based interconnect and cathode significantly increase the contact resistance. Metallic materials that are capable of developing stable oxide scales with acceptable growth rate and reasonably high electrical conductivity over the expected SOFC lifetime need to be developed.

Development of interconnect materials for solid oxide fuel cells

One of the challenges in improving the performance and cost-effectiveness of solid oxide fuel cells (SOFCs) is the development of suitable interconnect materials. The interconnect material is in contact with both the anode and the cathode, and thus must be stable with both electrode materials and in oxidizing and reducing environments. The interconnect material must also maintain a low electrical resistance during cell operation to avoid decreased efficiency due to ohmic losses. The common feature of the two approaches (metallic and ceramic) to the development of interconnect materials is the presence of chromium. The most promising ceramic materials are chromites, while the most promising metallic materials are chromia-forming alloys. The focus of this paper is comparison of metallic alloys for use as interconnects in solid oxide fuel cells, in terms of properties including oxidation resistance, volatility, electrical resistance and thermal expansion.

Metallic interconnects for solid oxide fuel cells

The high-temperature solid oxide fuel cell (SOFC) is the most efficient and environmentally friendly energy conversion technology to generate electricity from fuels such as hydrogen and natural gas as compared to the traditional thermal power generation plants. In the last 20–30 years, there has been significant progress in the materials development and stack technologies in SOFC. Among the electrode materials, lanthanum strontium manganite (LSM) perovskites, till today, are the most investigated and probably the most important electrode materials in SOFCs. The objective of this article is to review and update the development, understanding, and achievements of the LSM-based materials in SOFC. The structure, nonstoichiometry, defect model, and in particular the relation between the microstructure, their properties (electrical, thermal, mechanical, chemical, and interfacial), and electrochemical performance and performance stability are critically reviewed. Finally, challenges and prospects of LSM-based materials as cathodes for intermediate and low-temperature SOFCs are discussed.

W. Malléner

Papers

Compatibility of perovskite contact layers between cathode and metallic interconnector plates of SOFCs