A new catalyst developed at Brown combines an outer shell of platinum atoms with ordered layers of platinum and cobalt atoms in its nucleus. The neat layers help to tighten the shell and protect the cobalt, making the catalyst more reactive and durable, increasing the life of the hydrogen fuel cell.
A team of scientists from Brown University has developed a new catalyst that could make hydrogen fuel cell vehicles cheaper and more competitive.
This new technology is based on nanoparticles of an alloy of platinum and cobalt, for a new catalyst that is not only cheaper than pure platinum, but is also more efficient and durable.
Hydrogen fuel cells promise vehicles that, with the right infrastructure, combine the zero emissions of electric cars with the range and freedom of conventional fossil fuels.
However, for fuel cells to work, they need a catalyst to facilitate the oxygen reduction reaction.
Fuel cells contain a proton exchange membrane (PEMFC) with hydrogen on one side and oxygen-containing air on the other. In the reaction of reducing oxygen to generate electricity, the problem is that a catalyst is necessary for the reaction to work. Otherwise, the energy obstacle is very great.
Platinum is the main catalyst, but it is an expensive material, not very efficient and prone to impurities.
According to lead researcher Junrui Li, alloying platinum with metals like cobalt is cheaper and makes the catalyst more efficient, but the base metal oxidizes quickly under harsh conditions.
To avoid this, the Brown University team created nanoparticles that consisted of an outer layer of pure platinum and an interior constructed of alternating layers of platinum and cobalt atoms.
These layers enhance the reactive capabilities of platinum while preventing atoms from escaping in the reaction, increasing the life of the catalyst element.
“The arrangement of the atoms in the core layer helps to smooth and tighten the platinum lattice in the outer layer,” Shouheng said. “This increases the reactivity of the platinum and at the same time protects the cobalt atoms from being consumed during the reaction. That is why these particles outperform alloy particles with random arrangements of metal atoms. “
Tests of the new catalytic nanoparticles show that they have already outperformed platinum and remained active after 30,000 voltage cycles – one point on platinum drops dramatically.
However, the team stresses that what happens in a laboratory bench is different from what happens inside a fuel cell with higher temperature and acidity.
The new catalyst was sent to Los Alamos National Laboratory for further testing inside a real fuel cell.
The team says tests indicate that the new catalyst exceeds the goals set by the U.S. Department of Energy (DOE) for initial activity and long-term durability, with an initial activity of 0.56 amps per milligram and a activity after 30,000 cycles (equivalent to five years within a fuel cell) of 0.45 amps.
Even after 30,000 cycles, our catalyst still exceeded DOE’s target for initial activity. This kind of performance in a real-world fuel cell environment is really promising.
Research work on this type of catalyst will continue and a provisional patent application has already resulted.
All that remains is to test the new cobalt-platinum alloy in real conditions. If possible, replicate the Brown University laboratory experience in the real world.
Hydrogen car. Image: Zoran Karapancev Shutterstock
More information: news.brown.edu