Utilizing ammonia is seen as a promising strategy for hydrogen transport. Nevertheless, an effective method is required to convert it back into hydrogen and nitrogen.
A global research team has uncovered new findings regarding how an iron catalyst operates, enabling the breakdown of ammonia into nitrogen and hydrogen. Hydrogen is typically transformed into ammonia to facilitate easier transport. Thus, efficient catalysts are crucial for the reverse process, which restores ammonia to its original components. A collaborative effort involving researchers from the German Ruhr University Bochum, the Max Planck Institute for Chemical Energy Conversion (MPI CEC) in Mülheim an der Ruhr, Technische Universität Berlin, and the Italian Institute of Technology in Genoa details how the iron catalyst facilitates this reaction in the journal ACS Catalysis, published on September 6, 2024.
Making Hydrogen Transportable
Green hydrogen is seen as a viable energy carrier, produced by splitting water using renewable energy sources like wind or solar. However, often the locations needing hydrogen lack the appropriate conditions for water electrolysis. Transporting hydrogen requires it to be liquefied, which only occurs at extremely low temperatures. Converting hydrogen into ammonia, which can be liquefied at significantly higher temperatures, presents a favorable alternative. “Additionally, the chemical industry already possesses a well-established infrastructure for handling ammonia,” explains Professor Martin Muhler, Head of the Laboratory of Industrial Chemistry in Bochum and a Max Planck Fellow at MPI CEC.
To decompose ammonia (NH3) back into its original elements nitrogen (N2) and hydrogen (H2), efficient catalysts are necessary. A major challenge is that traditional iron catalysts typically encourage an unwanted reaction that produces iron nitride instead of nitrogen. In this research, the team explained the mechanisms behind this side reaction. They evaluated ammonia decomposition using a state-of-the-art catalyst from Clariant.
The experiment was conducted by Dr. Maximilian Purcel, Astrid Müller, and Professor Martin Muhler from Ruhr University Bochum and MPI CEC. Their findings were enhanced through intricate molecular dynamics simulations, bolstered by machine learning, executed by their partners in Italy. Moreover, the team from Technische Universität Berlin successfully identified the iron nitrides produced during the reaction through X-ray diffraction and monitored their changes.
Future Catalysts for Improved Efficiency
“Our discoveries will pave the way for the development of more effective catalysts for ammonia dissociation moving forward,” concludes Martin Muhler. “The synthesis and breakdown of ammonia have a longstanding history,” he notes. “We reference scientific studies from the past century, including the influential work of Martin Muhler’s doctoral advisor, Gerhard Ertl, who received the Nobel Prize for his contributions in 2007.”
