Harumi Yokokawa

Chapter 5 – Cathodes

Cathodes for solid oxide fuel cells (SOFC) should possess many properties, including high electrical conductivity, high catalytic activity for oxygen reduction, and compatibility with other cell components. The most important properties of cathodes are their catalytic activity for oxygen reduction and their compatibility with the electrolyte (including thermal expansion match and chemical non-reactivity). In addition to compatibility with the electrolyte, compatibility of the cathode with interconnect is also important. Both oxide ceramic and metallic materials are used as interconnects in SOFCs. As expected, these two types of interconnects present quite different issues in their compatibility with the cathode. In addition to compatibility with the electrolyte, compatibility of the cathode with interconnect is also important. Both oxide ceramic and metallic materials are used as interconnects in SOFCs. As expected, these two types of interconnects present quite different issues in their compatibility with the cathode. Generally, cathodes are made by powder processing routes. Cathode material powders are either made by solid state reaction of constituent oxides, or high surface area powders are precipitated from nitrate and other solutions as a gel product, which is dried, calcined and comminuted to give crystalline particles in the 1-10 μ m size range.