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Cleaning Solid Oxide Fuel Cells
Solid oxide fuel cells, which operate between 500° and 1000°C, transport oxygen through a ceramic material. At these temperatures, metals that catalyze hydrocarbon reforming reactions can also be incorporated so that conventional fuels such as methane can power the cell. One problem, however, has been rapid deactivation by sulfur impurities and carbon buildup. Yang et al. (p. 126; see the Perspective by Selman) report that doping of a barium zirconate-cerate with the rare-earths Y and Yb creates a material that transports both protons and oxygen ions at 750°C. This material, when used with nickel at the fuel cell anode, resists deactivation even when traces of hydrogen sulfide are present, apparently through enhanced ability to supply or remove water during surface reactions.
Abstract
The anode materials that have been developed for solid oxide fuel cells (SOFCs) are vulnerable to deactivation by carbon buildup (coking) from hydrocarbon fuels or by sulfur contamination (poisoning). We report on a mixed ion conductor, BaZr0.1Ce0.7Y0.2–xYbxO3–δ, that allows rapid transport of both protons and oxide ion vacancies. It exhibits high ionic conductivity at relatively low temperatures (500° to 700°C). Its ability to resist deactivation by sulfur and coking appears linked to the mixed conductor’s enhanced catalytic activity for sulfur oxidation and hydrocarbon cracking and reforming, as well as enhanced water adsorption capability.
