Anode materials are required to be electrochemically active toward the oxidation reaction of interest.  To be active as an anode, the material must be electronically (or mixed ionic/electronic (MIEC)) conducting under reducing environments, be chemically and physically stable, be a good electrocatalyst, and not react with other cell materials.  The material of choice must also be economically viable.  Traditionally, metal/ceramic composites (cermets) consist of an active metal species (usually nickel) and electrolyte (traditionally doped zirconia).  However, as this article details, there are a number of other nontraditional anode materials being studied, including ceria-based systems (which is more electrocatalytically active toward hydrocarbon-based fuels) and MIEC–ceramic systems.