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Decoding Atomic-Level Structures of the Interface between Pt Sub-nanocrystals and Nanostructured Carbon

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journal contribution
posted on 12.03.2018, 00:00 by Hongye Cheng, Ingvar Kvande, Yi-An Zhu, Nina Hammer, Magnus Rønning, John C. Walmsley, Ping Li, Zhiwen Qi, Xing-Gui Zhou, De Chen
Gaining an insight into the interface structure resulting from the interaction between metal nanoparticles and their supports, particularly under relevant reaction conditions, has been an important topic in heterogeneous catalysis and materials science. In this contribution, the active sites and interfaces of Pt sub-nanocrystals supported on carbon nanofibers (CNFs) are investigated and visualized at the atomic level by highly integrated X-ray absorption near-edge structure, X-ray absorption fine structure (EXAFS), and molecular dynamics (MD) simulations based on a reactive force field. Experimental and theoretical results indicate that the surface structure of the CNFs is one of the key parameters that governs the metal–support interface structure, which in turn determines the metal–support interaction strength and the structural properties of Pt clusters, including cluster size, Pt coordination number, and Pt–Pt bond length. Owing to the strong interaction between Pt and CNFs, sub-nanometer-sized Pt clusters are stabilized on CNFs. The Pt–Pt coordination number determined from EXAFS suggests Pt clusters of ∼1 nm size are deposited on platelet-type CNFs (p-CNFs), whereas clusters smaller than 0.6 nm are supported on fishbone-type CNFs (f-CNFs). The catalysts exhibit high selectivity toward CO oxidation at relatively low temperatures in the presence of H2, and their activity is related to the Pt coordination number and Pt–Pt bond length. The Pt clusters on the p-CNFs with relatively high coordination number have much higher activity than those on f-CNFs. The combined EXAFS analysis and MD simulations provide a better understanding of the catalyst properties at the atomic level and pave the way to use the CNF structure as a platform to tune the Pt particle size and metal activity through manipulating the metal–support interaction.