New material for fuel cells

MIT engineers claim to have improved the power output of direct methanol fuel cells (DMFCs) by more than 50 percent by developing a new material used for the electrolyte in the cell.

DMFCs currently on the market have limitations. One of which is that the material used for the electrolyte sandwiched between the electrodes is expensive. Even more important: the material, known as Nafion, is permeable to methanol, allowing some of the fuel to seep across the centre of the fuel cell. Among other disadvantages, this wastes fuel and lowers the efficiency of the cell.

Using a relatively new technique known as layer-by-layer assembly, the MIT researchers created an alternative to Nafion. The new material, they say, is also considerably less expensive than its conventional industrial counterpart.

'We were able to tune the structure of [our] film a few nanometres at a time,' said Paula Hammond, Bayer Professor of Chemical Engineering and leader of the research team. 'The result is (that we developed) a thin film that is two orders of magnitude less permeable to methanol but compares favourably 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.

The work was supported by the DuPont-MIT Alliance through 2007. It is currently supported by the US National Science Foundation.