Fuel cells are usually expensive because they use platinum as a catalyst. To make them more appealing to the market, researchers from the DOE’s National Accelerator Laboratory and the University of Houston, have created a new type of platinum catalyst, reducing the use of the pure metal down to 80 or even 70 percent, thus reducing the overall cost.
“This is a significant advance,” said scientist Anders Nilsson, who conducts research at the Stanford Institute for Materials and Energy Sciences, a joint institute between SLAC and Stanford University. “Fuel cells were invented more than 100 years ago. They haven’t made a leap over to being a big technology yet, in part because of this difficulty with platinum.”
Fuel cells dissociate water into hydrogen and oxygen, and currently require about 100 grams of platinum, which sends the price of one unit into the thousands of dollars category.
Platinum has been chosen because it is the only material that is strong enough to break the hydrogen-oxygen bonds, but does not bind to the free oxygen atoms too strongly. Other materials either can’t break apart the oxygen atoms, or bind to the released oxygen, which makes them unusable.
In 2005, Peter Strasser from the University of Houston began his quest in finding a solution to this problem by not replacing the platinum, by making it more reactive. He used a process called “dealloying”. He combined platinum with varying amounts of copper, and created a copper-platinum alloy, and then removed the copper from the surface region – the dealloying process. The resulted platinum material was discovered to be even more effective than it would otherwise had been.
The explanation to what happens to the alloy has been given by studying it with an X-ray beam. The phenomenon is called lattice strain – or the rearrangement or the platinum atoms closer together. This causes oxygen atoms to bond more weakly to the platinum, making the alloy better for use in fuel cells. “The distance between two neighboring atoms affects their electronic structure,” Strasser said. “By changing the interatomic distance, we can manipulate how strongly they form bonds.”