Power Cells Find Uses for Fossil Fuel

Article excerpt

A new fuel cell that runs on hydrocarbons such as natural gas, butane, and diesel could be an efficient, practical way to generate power without pollution.

Unlike typical fuel cells, which run on hydrogen, this new device oxidizes fossil fuels to produce electricity. Hydrogen fuel cells produce only water as a by-product, making them an attractive power source for electric cars. Storing volatile hydrogen onboard a vehicle raises worries about safety, however.

Some existing fuel cells do make use of hydrocarbons like gasoline, but they work by reforming the fuel first--that is, by stripping off the hydrogen gas (SN: 11/1/97, p. 279). This extra step reduces the fuel cell's efficiency.

"We can run the [new] fuel cell directly on hydrocarbon fuels, avoiding the reforming step," says Raymond J. Gorte of the University of Pennsylvania in Philadelphia. He and his colleagues John M. Vohs and Seungdoo Park describe their work in the March 16 NATURE.

Like all fuel cells, the device generates electricity by means of an electrochemical reaction. At the cathode, oxygen picks up electrons to form negatively charged oxygen ions. The ions diffuse through a membrane made of a compound known as yttria-stabilized zirconia. At the anode, the oxygen ions react with hydrocarbons to generate carbon dioxide, water, and electrons at a higher potential energy. Fuel cells with this design are known as solid-oxide fuel cells.

The researchers were able to solve a problem that has limited the usefulness of these cells. Graphite from the partial oxidation of hydrocarbons tends to build up on the anode, which is usually made of a nickel and yttria-stabilized zirconia composite. …