PerspectiveMaterials Science

Poison-Tolerant Fuel Cells

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Science  02 Oct 2009:
Vol. 326, Issue 5949, pp. 52-53
DOI: 10.1126/science.1180820

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Summary

A fuel cell electrode has three functions: allow access to reacting gases, provide active electrocatalytic sites, and allow transport of electrons as well as ions (1). High-temperature fuel cells generate electrical power by oxidizing the fuel electrochemically rather than by chemical combustion. They achieve this by digesting carbon-based fuels with the help of an internal catalyst. However, sulfur in the fuel gas is a potent poison for the nickel electrocatalyst used in the anodes of such cells currently. Nickel also has another disadvantage: When CH4 or higher hydrocarbons are used in a solid oxide fuel cell (SOFC) with a state-of-the-art nickel cermet (ceramic-metal composite) anode—that is, Ni-YSZ (yttria-stabilized zirconia)—carbon deposition, which reduces the activity of the anode, can occur if the steam-to-carbon ratio of the fuel gas is too low. Nickel effectively functions as a catalyst for carbon deposition (coking), thereby blocking the active sites of the anode and, in the worst case, destroying its structure. On page 126 of this issue, Yang et al. (2) demonstrate that an alternative material can be used for the anode of the SOFC, one that provides enhanced tolerance to both poisoning and coking.