A team of researchers at MIT has created a method that may significantly increase the efficiency of electrodes in one type of methanol fuel cells, which are considered promising as a replacement for batteries in portable electronic devices. Fuel cells are a potential future energy source, but their advantage of zero emissions of greenhouse gases and other pollutants has so far been outweighed by their high cost, so researchers have been trying to find ways to make the devices less expensive.
Because their electrodes are made of platinum, the higher the efficiency, the less of the expensive metal is needed to produce a given amount of power. The secret to the jump in efficiency, lies in changing the electrodes surface texture. Rather than leaving it smooth, the researchers gave it tiny stairsteps, which roughly doubled the electrode’s capacity to catalyze oxidation of the fuel and thus produce electric current. It is believed that further development of these surface structures could end up producing much greater increases, yielding more even electric current for a given amount of platinum.
Results are detailed in the Oct. 13 issue of the Journal of the American Chemical Society. In the experiments, researchers used platinum nanoparticles deposited on the surface of multi-wall carbon nanotubes. Many experiments have been done using platinum nanoparticles for fuel cells, but the results of the effects of particle size so far have been contradictory and controversial.
This work demonstrates that the important factor is not the size of the particles, but the details of their surface structure. The steps in the surface seem to provide a site where it’s easier for atoms to form new bonds, say researchers. Also, the team has shown that the step structures are stable enough to be maintained over hundreds of cycles, and stability is vital to being able to develop practical and effective direct methanol fuel cells.