Now researchers at Georgia Tech [ Lui et al., DOI: 10.1126/science.1174811] have developed an anode material that resists the buildup of sulfur and carbon that can occur at lower temperatures. With further development, the material might be incorporated into cheaper solid-oxide fuel cells that run efficiently at lower temperatures.
Solid-oxide fuel cells generate an electrical current by pulling oxygen from the air and using it to oxidize fuel at temperatures up to about 1,000 °C. Oxygen comes in through the cathode, fuel enters through the anode, and the two react in the electrolyte to make water and carbon dioxide, which flow out of the cell as waste. Electrons freed during the reaction are pulled into an external circuit. Solid-oxide fuel cells are currently used for stationary applications such as powering building furnaces. They might also be used in power plants to generate electricity from gasified coal, an application the U.S. Department of Energy is pursuing.
The chemical reactions in solid-oxide cells are sped by a catalyst, usually nickel, in the anode. Nickel is cheaper than the platinum catalysts used in other fuel cells, and this cost savings is one of the advantages of solid-oxide fuel cells. But nickel is prone to contamination by sulfur in the fuel, and it can get covered in carbon residue, particularly at low temperatures. Both of these factors tend to clog the cell and reduce performance.
The new anode material resists sulfur poisoning and carbon coking, even when running at low temperatures, and without compromising performance. The material has currently been tested over a period of 1,000 hours at temperatures ranging from 500 °C to 700 °C.
Liu is talking to companies about licensing the anode material. But before it can be brought to market, the new anode will have to be tested over longer periods of time in larger prototypes, he says.