The fact that chemistry professor Frank de Groot wears cowboy boots is in keeping with the adventurous nature of his research. With his team, De Groot is researching the electron structure of nano particles with immense radiation from synchrotons in Europe, Taiwan, the US, and Japan, which will make catalysis possible. De Groot says, “I do not study catalysis, but the catalyser: I want to understand the material better.” His ERC Advanced Grant makes it possible to see the electrons of iron oxide and cobalt oxide in detail. The combination of physics and chemistry and of theory and experiment in his work is unique.
If you are wondering what a material looks like, then most people think about the solid structure of the material and, if they zoom in, about molecules and atoms. De Groot is not so much studying this atom structure, but the structure of the electrons, energy structures that swirl around the nuclei of atoms like clouds. “This structure is not static – electrons move almost at the speed of light. The distribution of electrons across the material determines its characteristics,” explains De Groot. “To measure the electrons that are active in the catalysis process, we use x-ray spectroscopy. In a synchrotron you can vary the energy of this, as a result of which we are able to gain a picture of the electrons in detail bit by bit.” The number of synchrotrons in the world is small. “The one in Taiwan for example has a diameter of only 100 metres, but is ideal for our measurements because of the unique concept of the x-ray emission beamline. Following the timetable, the researchers from Utrecht may carry out measurements for approximately four days at a time, so we work 12 hours on, and 12 hours off.“
The research methods in x-ray spectroscopy have made huge advances in recent decades. “We used to work mainly with x-ray absorption. The resolution improved by a factor of ten while I was doing my PhD. Each spectrum that we were able to measure was new. The good thing was that the forecasts we calculated based on our theory turned out to be correct time after time. That has now been joined by the technology of x-ray emission. Since about five years, it has enabled us to take measurements with an even greater energy resolution.”
It is impossible to research the characteristics of one single electron. Because electrons strongly correlate, especially in elements like iron and cobalt, and the whole cloud has an effect on the individual particles, the whole system has to be described. “The remarkable thing about our research is that we are combining physics and chemistry. And we are also combining theory and experiment. The composition of my research team is very much in keeping with this, consisting as it does of four physicists, five chemists, and two theoreticians.” Together, these researchers cover a wide range of scientific activities. They focus on the development of theory, data analysis, software development, and experiments. The high resolution enables the research team to measure new spectra and to improve theory. On the basis of this, De Groot can develop new software for better calculations. These calculations function in turn as the basis for forecasts about the characteristics of the materials.
The ERC project has only been underway for a year, but De Groot already knows that the bar is high. “Measuring one percent divalent iron, while 99 percent trivalent iron attempts to disrupt the measurement, is probably more difficult than we thought.”
It would perhaps be logical for De Groot to become a research director in the US, among the experts working with a synchrotron. However, he cherishes the freedom of research that he enjoys in the Netherlands. “I would have to spend a lot of time there on the public relations side, but I would rather develop theory and set up experiments. I enjoy going on journeys of discovery with my team of researchers here in Utrecht.”
Text: Youetta Visser