Sulfur-tolerant cermet anodes

Abstract

The surface chemical behavior of the materials chosen for SOFC anodes determines the specification of a compatible fuel for reliable long-term operation. With the conventional nickel-zirconia cermet, for example, a hydrogen-carbon monoxide mixture can be used. Hydrocarbons on the other hand require a pre-reforming to avoid anode damage due to carbon precipitation. Impurities in the fuel may be incompatible with either the anode material or the reforming catalyst, with potentially serious consequences. The cost of an adequate fuel processing subsystem is not negligible, and its reliability is critical. More robust and impurity-tolerant anodes could therefore significantly accelerate the practical acceptance of solid oxide fuel cells. One option, of course is to introduce innovative anode materials. However given the established engineering experience, and the very satisfactory electrochemical performance of nickel-stabilized zirconia cermet anodes, the other possibility is surface modification to provide a chemically more robust metal surface, resistant to poisoning by impurities. Initial work in that direction, involving introduction of heavy transition metal species as catalysts, is here reported.