May 15 2009 / by Garry Golden
Category: Energy Year: General Rating: 2 Hot
The nanoscale design of basic energy components is once again revealing new solutions to the historical problems of high cost alternative energy systems.
Materials scientists from Washington University in St. Louis and Brookhaven National Laboratory have designed a nanostructured bimetallic (platinum and palladium) fuel cell catalyst that is 'efficient, robust and two-to-five times more effective than existing commercial catalysts.'
Fuel cells are important as 21st century 'power plants' that produce electricity on demand without a grid connection. Fuel cells can be designed as small as a AA battery (for portable gadgets), a breadbox (for electric vehicles), a small refrigerator (for home power) or the size of a small room (for utility power generation).
Commercialization of fuel cells depends on our ability to lower the costs of core membranes (MEAs) that convert chemical energy into electricity.
So what is the way forward? Nanostructured design of key membrane components.
Rethinking Surface Area & Shape
Team leader Professor Younan Xia explains the importance of the breakthrough: "There are two ways to make a more effective catalyst," Xia says. "One is to control the size, making it smaller, which gives the catalyst a higher specific surface area on a mass basis. Another is to change the arrangement of atoms on the surface. We did both. You can have a square or hexagonal arrangement for the surface atoms. We chose the hexagonal lattice because people have found that it's twice as good as the square one for the oxygen reduction reaction (which determines the electrical current generated)."
To reduce costs and improve performance the team experimented with new core and branching structures. The catalyst has a core made of palladium which branching arms (‘dendrites’) of platinum that are seven nano-meters long.
According to Xia's team release: ‘At room temperature operation the team’s catalyst was two-and-a-half times more effective per platinum mass for this process than the state of the art commercial platinum catalyst and five times more active than the other popular commercial catalyst. At 60 degrees C (the typical operation temperature of a fuel cell), the performance almost meets the targets set by the U.S. Department of Energy.’
The next step for the team?
Integrating gold as a third metal catalyst to deal with the problem of carbon molecules that reduces performance by binding and blocking valuable surface area.
The study was published in the online journal Science.
University of Washington St Louis Press Release