Fuel Cells in the Basement

Fuel cells have been touted as the environmentally sound replacement for everything from AAA batteries to the massive steam turbines that run our power plants. Although they were first described more than 150 years ago, they have proved to be frustratingly difficult to commercialize, due to problems of cost, reliability, and size.

The type of fuel cell that has received the most attention in recent years is one that uses hydrogen as a fuel. At first glance, this type of fuel cell is exceptionally clean, producing nothing but water and heat as byproducts. Currently, the majority of commercially available hydrogen is produced from hydrocarbons by an energy-consuming process, which also produces carbon dioxide, a greenhouse gas. In addition, the difficulty of storing and distributing hydrogen is a significant issue. As chemical engineer Steven McIntosh observes, “The hydrogen economy will be a long time coming.”

McIntosh focuses on solid oxide fuel cells that can use any combustible fuel, including gasoline, diesel, and biofuel. “Because they take advantage of existing infrastructure, solid oxide fuel cells will give us the ability to realize the potential of fuel cells in the near future,” he says.

In design, fuel cells are much like batteries, which also convert chemical energy into electricity. A battery has an electrolyte and two electrodes, at least one of which is made of a solid metal. This metal electrode is converted to another compound during the generation of electricity, and when this metal is exhausted, the battery dies.

In a fuel cell, the electrodes serve as a catalyst as well as a conductor, while the fuel itself is provided by an external source. In a solid oxide system, hydrocarbon fuel and air are supplied to the cell. Oxygen from the air is reduced to negatively charged oxygen ions in the cathode of the fuel cell. These ions are transported through the electrolyte to the anode, where they electrochemically combust the hydrocarbon fuel to form water, carbon dioxide, and heat. The electrons released by this reaction cannot penetrate the electrolyte and so flow to the cathode through an external electrical circuit, providing power that is generated as long as fuel is supplied to the cell. Although carbon dioxide is still emitted, its formation contributes to the power output of the fuel cell.

McIntosh is working to find high-performance anode materials that provide the ideal balance of catalysis and conductivity. The requirements for these materials are especially stringent as solid oxide fuel cells require temperatures of over 700 degrees C to operate; in addition, the ideal anode would also suppress the formation of carbon which is a byproduct of transforming hydrocarbons into electricity.

McIntosh’s approach is to develop a library of possible mixed oxide materials that may prove useful as an anode and subject each of them to a series of tests that help him better understand their properties. “We know that if you pull oxygen out of these materials, you improve the conductivity,” he says, “but we are still trying to understand the limiting factors.” In McIntosh’s view, solid oxide fuel cells would be ideal for home use and distributed power generation. “Because they could be used to generate heat as well as electricity, they are more efficient than traditional energy sources—and they would be considerably more versatile since they are not limited to a single kind of fuel,” he says. “but we are still trying to understand the limiting factors.” In McIntosh’s view, solid oxide fuel cells would be ideal for home use and distributed power generation. “Because they could be used to generate heat as well as electricity, they are more efficient than traditional energy sources—and they would be considerably more versatile since they are not limited to a single kind of fuel,” he says.