Synthetic materials, the structure of which is similar to that of a natural perovskite mineral, are particularly popular when it comes to more powerful solar cells. Now researchers in Vienna have discovered that they have completely different, perhaps even more exciting properties. They can be used to wrest an oxygen atom from the climate gas carbon dioxide. What remains is carbon monoxide, an important raw material for chemistry, from which synthetic fuels can also be produced.
Image: Vienna University of Technology
Green electricity supplies the energy
"We are interested in what is known as the reverse water-gas shift reaction," says Professor Christoph Rameshan from the Institute for Materials Chemistry at the Vienna University of Technology. “In the process, carbon dioxide and hydrogen are converted into water and carbon monoxide. So that no new greenhouse gas is created, the hydrogen used is produced by electrolysis, i.e. the splitting of hydrogen, with green electricity providing the energy.
This reaction is not new, but it is still a long way from industrial use. Because the reaction requires high temperatures, the catalysts used do not last long. Replacing them over and over again is not economically feasible because they contain valuable metals and are therefore expensive..
Perovskite with excellent properties
Rameshan and his team go in search of cheap catalysts. They found what they were looking for in perovskite structures. They are characterized by a large number of pores, which promise a large reaction surface. “We tried a lot and finally came across a perovskite made of cobalt, iron, calcium and neodymium, which has excellent properties,” says Rameshan.
Due to the crystal structure of perovskite, certain atoms can migrate through it. During catalysis, for example, cobalt atoms penetrate from the interior of the material to the surface and form tiny nanoparticles that are particularly chemically active. At the same time, so-called oxygen voids are created - positions in the crystal where an oxygen atom should actually be located. It is precisely at these vacant spots that CO 2 molecules can dock particularly well in order to then be broken down into oxygen and carbon monoxide.
Three times as expensive, but lasts much longer
The new catalyst is three times as expensive as the reaction accelerators that were previously only used in the laboratory. However, it makes up for this with a longer service life. If it does fall asleep, it can be regenerated so that it can be used again. Reactors that crack carbon dioxide could be used in industrial plants that generate a lot of greenhouse gas.