null Researchers from the University of Jyväskylä and Xiamen University discover how a nanocatalyst operates at the atomic level

Researchers from the University of Jyväskylä and Xiamen University discover how a nanocatalyst operates at the atomic level

Tommi Kutilainen

Researchers from the Nanoscience Center at the University of Jyväskylä in Finland and Xiamen University in China have discovered how nano-scale copper particles, whose atomic structure is known in detail, operate during the modification of carbon–oxygen bonds, when ketone molecules are transformed into alcohol molecules. The modification of carbon–oxygen bonds and carbon–carbon bonds, which are present in organic molecules, is an important step in catalytic reactions where a source material is transformed into valuable end products.

Understanding how catalysts operate at the atomic structure level of a single particle will enable their development towards a specific end goal, for example by making them more effective and selective for the purposes of a desired end product. The results of the research have been published in the internationally renowned nanoscience journal ACS Nano. In Finland, the research project was led by Academy Professor Hannu Häkkinen from the University of Jyväskylä.

A collaboration that combined experiments with simulations

The catalytic copper particles that were used in the research were manufactured in Xiamen University, and their role in the modification of strong carbon–oxygen bonds during the hydrogenation reaction process was studied using a computer simulation developed by researchers in the Nanoscience Center at the University of Jyväskylä. The detailed atomic structure of the copper particles was determined with the help of X-ray diffraction and nuclear magnetic resonance (NMR) spectroscopy.

The researchers utilised around two million CPU hours of CSC's supercomputer Sisu's CPU time. It was determined that a cluster contained 25 copper atoms and 10 hydrogens, and that the surface of the cluster was protected by 18 thiol molecules.

–  At first, we simulated the electron structure of a copper hybrid cluster. On the basis of our simulations, we determined that the ten hydrogens that are present in the cluster play an important role in the stabilisation of the cluster's atomic structure so that it remains in the same form that it was discovered in. Most of the CPU time was spent on studying the detailed mechanisms present in the hydrogenation reactions. Based on these results, we were able to predict the most likely reaction mechanism, explains Hannu Häkkinen.

The simulations predicted that the hydrogens that were bound to the particle's copper core acted as a type of hydrogen stock that would transfer two hydrogen atoms to the carbon–oxygen bond during a single reaction. After the reaction, the hydrogen stock is replenished when a hydrogen molecule from the surrounding environment that was caught in the particle would split into two hydrogen atoms that would then be bound to the copper core. The NMR studies that were conducted in Xiamen revealed the intermediate product of the reaction, which confirmed the predictions provided by the computational model.

– This is one of the first times in the world that people have combined experiments with simulations to determine how a structurally well-known catalyst particle operates.

– CSC's calculation resources played a critical role in this project, as they allowed us to efficiently perform all of our simulations in quite a short amount of time, notes Hannu Häkkinen.

Looking for efficient and affordable catalysts

– Traditionally, hydrogenation reactions utilise expensive platinum-based catalysts. Our work has demonstrated that nano-scale copper hybrid particles can also act as hydrogenation catalysts. These results have given us hope that, in the future, we will be able to develop efficient and affordable copper-based catalysts that can be used to transform functionalised organic molecules into higher added-value products, says Professor of Computational Catalysis Karoliina Honkala, who is Hannu Häkkinen's research partner.

Häkkinen's and Honkala's research also involved other people from the University of Jyväskylä: Postdoctoral Researcher Nisha Mammen, Doctoral Candidate Sami Kaappa and Senior Researcher Sami Malola. The research that is conducted by Häkkinen's and Honkala's groups is supported by the Academy of Finland. The computer simulations that were used in the research were run on CSC – IT Center for Science supercomputers. Professor Nanfeng Zheng's group from Xiamenin University also participated in the research.

Photo: The atomic structure of a copper catalyst used in a carbon–oxygen bond hydrogenation reaction. Formaldehyde, or H2CO (left), the model molecule used in the simulations, captures two hydrogens from the copper, which are then transferred to the carbo–oxygen bond in a way that the molecule is transformed into a simple alcohol (methanol, or CH3OH, right).  After the reaction, the hydrogen molecule present in the environment (blue, left) splits into two hydrogen atoms inside the copper. Photo: Sami Malola, University of Jyväskylä.

Further information:

This article is based on a press release published by the Academy of Finland.