Palladium power

Two Brown University chemists have created a means of producing palladium nanoparticles that could prove useful to developers of fuel cells.

The scientists produced the palladium nanoparticles with about 40 per cent greater active surface area than commercially available palladium particles, and the nanoparticles remained intact four times longer.

Palladium is far cheaper than another popular fuel cell catalyst, platinum, and it is also more abundant.

But researchers have previously wrestled with creating palladium nanoparticles with a large enough active surface area to make catalysis efficient in fuel cells while preventing the particles from clumping together during the chemical processes that convert a fuel source to electricity.

Brown chemistry professor Shouheng Sun and graduate student Vismadeb Mazumder created the 4.5 nanometre palladium nanoparticles and then attached them to the carbon anode of a direct formic acid fuel cell.

The researchers then did something new. They used weak-binding amino ligands to keep the palladium nanoparticles separate and uniform in size, increasing the available surface area on the anode, raising the efficiency of the fuel cell reaction.

What is also special about the ligands is that they can be 'washed' from the carbon without jeopardising the integrity of the separated palladium nanoparticles. This is an important step, Mazumder said, because previous attempts to remove binding ingredients have caused the particles to lose their rigid sizes and clump together.

The Brown team said in experiments lasting 12 hours, their catalyst lost 16 per cent of its surface area, compared to a 64 per cent loss in surface area in commercial catalysts.

The research was funded by the Division of Materials Research of the National Science Foundation and a Brown seed fund.