Textured electrodes double fuel-cell efficiency

Textured electrodes double fuel-cell efficiency

A team of researchers at the Massachusetts Institute of Technology in Cambridge, MA, led by associate professor Yang Shao-Horn of MIT’s Department of Materials Science and Engineering and working with other researchers at Brookhaven National Laboratory and the Japan Institute of Science and Technology, has found that texturing promises to dramatically increase the efficiency of the electrodes in methanol fuel cells.

Methanol fuel cells are considered to be promising replacements for batteries in portable electronic devices, but their cost has been prohibitive, due mainly to the cost of their platinum electrodes. By significantly increasing electrode efficiency, much less platinum would be needed to produce a given amount of power. The key to boosting efficiency was changing the surface texture of the electrode — instead of leaving it smooth, the researchers gave it tiny stair steps. This approximately doubled the electrode’s ability to catalyze the fuel oxidation reaction that produces an electric current.

To create the new texture, the team used platinum nanoparticles deposited on the surface of multiwall carbon nanotubes. Many people have experimented with the use of platinum nanoparticles for fuel cells, but the experiments involving the effect of particle size on the activity has so far been contradictory and controversial. The MIT researchers’ work shows that the key factor is not particle size, but the details of their surface structure. The team has also shown that the step structures are stable enough to be maintained over hundreds of cycles — essential for developing practical methanol fuel cells.

Believing that further development may end up producing far greater increases, the team is working on creating surfaces with even more steps to try to boost activity even further. Shao-Horn suggests that edges seem to provide a site where it’s easier for atoms to form new bonds, and so the addition of steps would create more of these active sites. Theoretically, it should be possible to enhance the activity by orders of magnitude.

The team also hopes to discover in the next few months whether the steps enhance the other key fuel-cell process — oxygen reduction. For more information, call Yang Shao-Horn at 617-253-2259 or e-mail shaohorn@mit.edu.

Richard Comerford