Tunneling electron microscope image of a carbon nanotube decorated with platinum clusters (bright color).
Tunneling electron microscope image of a carbon nanotube decorated with platinum clusters (bright color).

As a very expensive metal, platinum is one of the bottlenecks hindering the growth of renewable energy. Platinum is used as the catalyst in electrolysers that store electric energy as chemical compounds, and it also plays an important role in fuel cells, catalytic converters and many chemical processes used by industry.

Now, however, a group of researchers at Aalto University in Finland, led by Tanja Kallio and Kari Laasonen, has developed a novel electrocatalyst that uses just one hundredth of the amount of platinum generally used in commercial electrocatalysts. Despite this, the new material, which takes advantage of the special characteristics of carbon nanotubes, has a similar activity to that of commercial electrocatalysts. The researchers report their results in a paper in ACS Catalysis.

“When platinum is electrodeposited on the surface of carbon nanotubes, it forms particles consisting of a couple of atoms. On other materials, such as graphene, platinum forms larger nanoparticles,” Kallio explains.

“We believe this is because the carbon atoms of the curved surface are in a strained state, which makes them prone to stabilizing platinum on the surface of the nanotube. This ensures that the platinum atoms form small and catalytically-active particles. Our modelling showed that the more strained the carbon bonds are, the better the stabilization of the platinum. Smaller tubes are more curved, which makes the strain greater, so the diameter of the nanotubes is also important.”

Electrolysers store energy in the form of hydrogen bonds. In practice, they are used to store the energy produced by fluctuating energy sources, such as wind energy, helping to balance the difference between demand and supply. Since the electrocatalyst accounts for approximately one third of the price of the electrolyser, reducing the amount of platinum needed would make the process significantly less expensive.

“In addition to the price of platinum, the availability of the metal is also a problem,” Kallio says. “Platinum is on the EU list of critical raw materials, which means that its use is problematic either due to its scarceness or due to geopolitical problems. This is why the EU is aiming to reduce the use of platinum.”

So far, the functionality of the electrocatalyst developed at Aalto University has only been proven in laboratory conditions. “In small-scale conditions and at room temperature, the electrocatalyst is stable and usable for a long time,” Kallio says. “The next step is to increase the scale of production and test the functionality of the electrocatalyst in practical applications, which are often carried out at a higher temperature.”

This story is adapted from material from Aalto University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.