CO 2 activation by Cu-based bimetallic clusters Olga V. Lushchikova and Paul Scheier Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Austria Among the greenhouse gases responsible for climate change, carbon dioxide (CO 2 ) is the most abundant, accounting for more than 80% of their total amount. Since the industrial revolution, the atmospheric CO 2 concentration has grown rapidly by more than 40% and reached 415 ppm in 2021.[1] Therefore, methods to reduce it are urgently needed. The main challenge of CO 2 utilization is its high thermodynamic stability and kinetic inertness with high dissociation energy exceeding 11 eV. Current industrial conversion of CO 2 to methanol proceeds with the use of a Cu/ZnO/Al 2 O 3 catalyst at elevated temperature and pressure, suggesting high activation barriers of elementary steps in the reaction mechanism.[2] Although an industrial copper-based catalyst thus exists, it has been suggested that the addition of other metals to the copper can modify its catalytic properties, potentially increasing the efficiency of methanol production.[3] This hypothesis is supported by experimental studies that have shown that bimetallic catalysts can outperform conventional industrial catalysts.[4] Despite these promising developments, the exact mechanism of methanol formation remains elusive. Knowledge of the elementary reaction steps at the molecular level is required for a rational design of better catalyst material. Since CO 2 is the prime reactant, its interaction with the active sites of the catalyst needs to be understood. Well- defined metal clusters in the gas phase offer the possibility to model the active sites and explore their interaction with CO 2 in detail. The reaction of CO 2 with metal ions is well studied, but much less information is available about the reaction with larger metal clusters and almost nothing about its reaction with bimetallic clusters, even though they appear to be very promising candidates for methanol synthesis. We are trying to fill this gap by conducting experiments to elucidate structural information of the reaction products formed upon reacting CO 2 with Cu-based bimetallic clusters. Bimetallic clusters are formed and reacted with CO 2 in superfluid helium nanodroplets (HNDs), which act as a nanoreactor. The application of HNDs allows for the highest level of control over cluster charge, size, and copper- to-dopant metal ratio, which will simulate the active sites of the catalyst. Formed complexes can be studied by means of collision-induced dissociation and He-tagging photo fragmentation spectroscopy. In this way, we will obtain detailed information on the binding nature of CO 2 to the cluster and could deduce how it depends on the cluster composition. References 1. NOAA Research. Trends in Atmospheric Carbon Dioxide https://www.esrl.noaa.gov/gmd/ccgg/trends/ (accessed Feb 22, 2021). 2. Artz, J. et al ; Sustainable Conversion of Carbon Dioxide: An Integrated Review of Catalysis and Life Cycle Assessment. Chem. Rev. 2018, 118 (2), 434–504. 3. Yang, Y.; White, M. G.; Liu, P. Theoretical Study of Methanol Synthesis from CO 2 Hydrogenation on Metal-Doped Cu(111) Surfaces. J. Phys. Chem. C 2012, 116 (1), 248–256. 4. Jiang, X. et al; CO 2 Hydrogenation to Methanol on Pd–Cu Bimetallic Catalysts with Lower Metal Loadings. Catal. Commun. 2019, 118, 10–14.
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