New membrane technology could improve fuel cell efficiency

Washington, Mar 20 : Researchers at Duke University's Pratt School of Engineering have developed a new type of membrane based on tiny iron particles that appears to address one of the major limitations exhibited by current power-generating fuel cell technology.

Fuel cells generally generate electricity as the result of chemical reactions between an external fuel, most commonly hydrogen, and an agent that reacts with it.

The membrane that divides the two parts of the cell and facilitates the reaction is a significant factor in determining the efficiency of the cell.

Usually, fuel cells are used in settings such as satellites, submarines or remote weather stations because they have no moving parts, do not require combustion and can run unattended for long periods of time.

However, this power-generating fuel cell technology loses efficiency as the temperature rises and the humidity falls.

Now, Duke University researchers have developed a membrane that enables fuel cells to operate at low humidity and theoretically to operate at higher temperatures.

"The current gold standard membrane is a polymer that needs to be in a humid environment in order to function efficiently," said Mark Wiesner, Ph.D., a Duke civil engineer and senior author of the study.

"If the polymer membrane dries out, its efficiency drops. We developed a ceramic membrane made of iron nanoparticles that works at much lower humidities. And because it is a ceramic, it should also tolerate higher temperatures," he added.

"If the next series of tests proves that fuel cells with these new membranes perform well at high temperatures, we believe it might attract the type of investment needed to bring this technology to the market," Wiesner added.

Nafion, the membrane most commonly used today was discovered in the 1960s. As the temperature rises, the polymer becomes unstable and the membranes dehydrate, causing a loss of performance.

Wiesner said that besides it's temperature and heat limitations, Nafion is also much more costly to produce than the new membrane and that the membrane make up as much as 40 percent of the overall cost of fuel cells.

According to Wiesner, the future tests will show the new membrane's ability to operate at higher temperatures.

"The efficiency of current membranes drops significantly at temperatures over 190 degrees Fahrenheit. However, the chemical reactions that create the electricity are more efficient at high temperatures, so it would be a big improvement for fuel cell technology to make this advance," he said.

An interesting outcome of these experiments is leading Wiesner down a new and related research path. As a result of the chemical reactions that create the electricity, small amounts of water are created as a byproduct.

"In the current technology, this water is used by the system to maintain the humidity within the cell. The water produced in these reactions is of high purity. So, if a fuel cell membrane could be developed that wasn't reliant on humidity, this water could be used for other purposes," Wiesner said.

The researchers also plan to study new ways of fabricating the membranes to improve their durability and flexibility.

The study is published online in the Journal of Membrane Science.

ANI