Operating constraintsSOFC’s must operate at high temperatures to enable diffusion of oxygen ions through the electrolyte made possible by reason of oxygen vacancies in the electrolyte crystalline structure. With conventional designs the anode is a composite of nickel and yttria-stabilised zirconia (YSZ). This composite is an electronic conductor (due to nickel) and also an ionic conductor (due to YSZ). Nickel, however, catalyses the formation of graphite from hydrocarbons, except for a narrow range of operating temperatures and only for methane, thus carbon formation with nickel based anodes is unavoidable for the wider range of hydrocarbon fuels available. Research reports suggest that anodes made from a composite of copper and ceria, or samaria-doped ceria, may remove this barrier in the future.
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