Brown University researchers have developed a new alloy catalyst that optimizes hydrogen fuel cell usage.
The new catalyst is said to exceed current targets for performing oxygen reduction reaction in a fuel cell.
The main deterrent stopping the widespread use of hydrogen fuel cells in vehicles is the cost of platinum catalysts.
Researchers have been proposing strategies of using less precious platinum by combining it with other cheaper metals. However, these alloy catalysts tend to degrade quickly in fuel cell conditions.
Brown University researchers have now come up with a new alloy catalyst that reduces platinum use and holds up well in fuel cell testing.
The catalyst, made from alloying platinum with cobalt in nanoparticles, was shown to beat the U.S. Department of Energy (DOE) targets for the year 2020 in both reactivity and durability, according to tests described in the journal Joule.
“The durability of alloy catalysts is a big issue in the field,” said Junrui Li, the study’s lead author. “It’s been shown that alloys perform better than pure platinum initially, but in the conditions, inside a fuel cell the non-precious metal part of the catalyst gets oxidized and leached away very quickly.”
To address this leaching problem, Li and his colleagues developed alloy nanoparticles with a specialized structure.
According to the researchers, the particles have a pure platinum outer shell surrounding a core made from alternating layers of platinum and cobalt atoms.
This layered core structure is key to the catalyst’s reactivity and durability, says professor Shouheng Sun, senior author of the research.
“The layered arrangement of atoms in the core helps to smooth and tighten platinum lattice in the outer shell,” Sun said. “That increases the reactivity of the platinum and at the same time protects the cobalt atoms from being eaten away during a reaction. That’s why these particles perform so much better than alloy particles with random arrangements of metal atoms.”
Initial testing showed that the catalyst performed well in the laboratory setting, outperforming a more traditional platinum alloy catalyst.
The new catalyst maintained its activity after 30,000 voltage cycles, whereas the performance of the traditional catalyst dropped off significantly.
Image and content: Sun lab/Brown University