The DMFCs currently on the market, however, have limitations. For example, the material currently used for the electrolyte sandwiched between the electrodes is expensive. Even more important: that material, known as Nafion, is permeable to methanol, allowing some of the fuel to seep across the center of the fuel cell. Among other disadvantages, this wastes fuel-and lowers the efficiency of the cell-because the fuel isn't available for the reactions that generate electricity.
Using a relatively new technique known as layer-by-layer assembly, the MIT researchers created an alternative to Nafion. We were able to tune the structure of [our] film a few nanometers at a time, Hammond said, getting around some of the problems associated with other approaches. The result is a thin film that is two orders of magnitude less permeable to methanol but compares favorably to Nafion in proton conductivity.
To test their creation, the engineers coated a Nafion membrane with the new film and incorporated the whole into a direct methanol fuel cell. The result was an increase in power output of more than 50 percent.
The team is now exploring whether the new film could be used by itself, completely replacing Nafion. To that end, they have been generating thin films that stand alone, with a consistency much like plastic wrap.
This work was supported by the DuPont-MIT Alliance through 2007. It is currently supported by the National Science Foundation.
In addition, Hammond and colleagues have begun exploring the new material's potential use in photovoltaics. That work is funded by the MIT Energy Initiative. This Institute-wide initiative includes research, education, campus energy management and outreach activities, an interdisciplinary approach that covers all areas of energy supply and demand, security and environmental impact. For more information, please visit http:
|Contact: Elizabeth Thomson|
Massachusetts Institute of Technology