Precise nanoscale engineering of bimetallic catalysts allows scientists to boost hydrogenation performance by fine-tuning electronic structures.
Bimetallic particles, made from a combination of a noble metal and a base metal, have unique catalytic properties that make them highly effective for selective heterogeneous hydrogenation reactions. These properties arise from their distinctive geometric and electronic structures. For hydrogenation to be both effective and selective, it requires specific interactions at the molecular level, where the active atoms on the catalyst precisely target the functional group in the substrate for transformation.
Nanoscale Engineering and Electronic Structure Tuning
Scaling these particles down to nanoscale atomic clusters or single-atom alloys further enhances their catalytic performance. This reduction in size increases surface dispersion and optimizes the use of noble metal atoms. Additionally, these nanoscale changes alter the electronic structure of the active sites, which can significantly influence the activity and selectivity of the reaction. By carefully adjusting the bonding between noble metal single atoms and the base metal host, researchers can create flexible environments that fine-tune the electronic properties needed to activate specific functional groups. Despite these advances, achieving atomically precise fabrication of such active sites remains a significant challenge.
Breakthrough Study on Atomic Site Regulation
In a study published in Chem, a team led by Prof. Wenjie Shen and Prof. Yong Li from the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences (CAS), collaborating with Prof. Weixue Li from the University of Science and Technology of China of CAS and Prof. Yuemin Wang from Karlsruhe Institute of Technology in Germany, successfully regulated the atomic structure of active sites for hydrogenation reaction.
Researchers first developed a method to densely populate and precisely position isolated Pt atoms in the form of Pt-Fe-Pt heterotrimer on α-Fe nanoparticles. The Pt-Fe-Pt heterotrimer was achieved by H2-reduction of a Pt-Fe2O3 particle pair, where a 3.3 nm Pt particle sits on a 9.8 nm Fe2O3 particle. During the H2 reduction, iron oxides were reduced to iron, facilitating the dispersion of Pt particles into Pt-Fe-Pt heterotrimers on the surface of iron particles via surface alloying.
Enhanced Hydrogenation and Pathway Discovery
In addition, researchers uncovered the formation pathway and coordination environment of the Pt-Fe-Pt heterotrimer. In the gas-phase hydrogenation of crotonaldehyde, the Pt-Fe-Pt heterotrimer showed a preference for hydrogenated the C=O bond to produce crotyl alcohol rather than the conjugated C=C bond. The intrinsic hydrogenating rate increased by 35 times, effectively resolving the activity-selectivity trade-off in hydrogenation reactions.
Molecular-Level Insights into Catalytic Function
Furthermore, researchers revealed a site-bond recognition pattern of the Pt-Fe-Pt heterotrimer. The left-end Pt atom anchored the C=C bond, while the central Fe atom activated the C=O bond, which was further hydrogenated by H atoms adsorbed on the right-end Pt atom.
“Our study quantifies the surface catalytic reaction at the molecular level and offers a strategy for tailoring active sites on bimetallic catalysts with atomic precision,” said Prof. Shen.
Reference: “Fine-tuned coordination environment of Pt-Fe-Pt active site for selective heterogeneous hydrogenation of crotonaldehyde” by Di Zhou, Junjun Wang, Minzhen Jian, Yong Li, Zheng Jiang, Shuang Liu, Yan Zhou, Jiake Wei, Christof Wöll, Wei-Xue Li, Yuemin Wang and Wenjie Shen, 3 January 2025, Chem.
DOI: 10.1016/j.chempr.2024.11.018
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