For the first time, researchers at Stockholm University have been able to examine the surface of iron and ruthenium catalysts during the formation of ammonia from nitrogen and hydrogen; their findings have been published in the scholarly journal Nature.
Artificial fertilizers in agriculture, which are often spread in the form of small grains, have contributed to much higher harvests and thereby saved 4 billion people’s lives during the 20th Century. In the study, the researchers show how ammonia is produced in a catalytic process, forming the basis for the production of fertilizers. Image Credit: GUDELLAPHOTO/Mostphotos
An eco-friendly shift in the existing highly carbon-intensive chemical industry is made possible by advances in understanding the catalytic process and the potential to discover even more efficient materials.
With an annual production of 110 million tons, ammonia is one of the most important base chemicals used worldwide to manufacture fertilizers. The Haber-Bosch process generates it.
Given that the Haber-Bosch process has prevented mass famine and saved the lives of around 4 billion people, the journal Nature suggested in 2001 that it was the most important scientific discovery made by humans in the 20th Century. An estimate of the nitrogen content in the proteins and DNA of human bodies indicates that Haber-Bosch accounts for half of the atoms.
In spite of 3 Nobel Prizes (1918, 1931, and 2007) for the Haber-Bosch process, it has not been possible to experimentally investigate the catalyst surface with surface-sensitive methods under real ammonia production conditions; experimental techniques with surface sensitivity at high enough pressures and temperatures had not been achievable.
Anders Nilsson, Professor, Department of Chemical Physics, Stockholm University
Anders Nilsson continued, “Consequently, different hypotheses about the state of the iron catalyst as being metallic or in a nitride, as well as the nature of the intermediate species of importance to the reaction mechanism, could not be unambiguously verified.”
New Instrument Built at Stockholm University
What enabled this study is that we have built a photoelectron spectroscopy instrument in Stockholm that allows studies of catalyst surfaces under high pressures. Thereby, we have been able to observe what happens when the reaction occurs directly. We have opened a new door into understanding ammonia production catalysis with our new instrument, where we can now detect reaction intermediates and provide evidence for the reaction mechanism.
David Degerman, Postdoc, Chemical Physics, Stockholm University
Patrick Lömker, Researcher at Stockholm University, said, “To have our Stockholm instrument at one of the brightest x-ray sources in the world at PETRA III in Hamburg has been crucial to conducting the study. We can now imagine the future with even brighter sources when the machine upgrades to PETRA IV.”
We now have the tools to conduct research leading to new catalyst materials for ammonia production that can be used better to fit together with electrolysis-produced hydrogen for the green transition of the chemical industry.
Anders Nilsson, Department of Physics, Stockholm University, Sweden.
Can Lessen the Dependence on Fossil Sources
Bernadette Davies, Ph.D. Student in Materials Chemistry at Stockholm University, said, “It is inspiring to conduct research on a topic that is so linked to a scientific success story that has helped humanity tremendously. I am eager to continue research to find new catalysts that can lessen our dependence on fossil sources. The chemical industry alone accounts for 8% of the worldwide CO2 emissions.”
Sergey Koroidov, Researcher at Stockholm University explained, “The long-term prospect of carrying out ammonia production through an electrocatalytic alternative that is directly driven by solar or wind electricity is most appealing, and now we have tools to scientifically assist in this development.”
The research was carried out in association with Deutsches Elektronen-Synchrotron (DESY) in Hamburg and the Montan University in Austria. Former University staff members Chris Goodwin, Peter Amann, Mikhail Shiplin, Jette Mathiesen, and Gabriel Rodrigez were involved in the project.
Journal Reference:
Goodwin, C. M., et.al., (2024). Operando probing of the surface chemistry during the Haber–Bosch process. Nature. doi.org/10.1038/s41586-023-06844-5