Formation and Location of Pt Single Sites Induced by Pentacoordinated Al Species on Amorphous Silica-Alumina

Yutong Zhao; Lizhuo Wang; Alena Kochubei; Wenjie Yang; Haimei Xu; Yongming Luo; Alfons Baiker; Jun Huang; Zichun Wang; Yijiao Jiang

doi:10.1021/acs.jpclett.1c00139

Formation and Location of Pt Single Sites Induced by Pentacoordinated Al Species on Amorphous Silica-Alumina

J Phys Chem Lett. 2021 Mar 18;12(10):2536-2546. doi: 10.1021/acs.jpclett.1c00139. Epub 2021 Mar 8.

Authors

Affiliations

¹ School of Engineering, Macquarie University, Sydney, New South Wales 2109, Australia.
² Laboratory for Catalysis Engineering, School of Chemical and Biomolecular Engineering, The University of Sydney, Sydney, NSW 2006, Australia.
³ Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500, China.
⁴ Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zürich, Hönggerberg, HCI, Zurich CH-8093, Switzerland.

PMID: 33683898
DOI: 10.1021/acs.jpclett.1c00139

Abstract

Alumina and its mixed oxides are popular industrial supports for emerging supported metal catalysts. Pentacoordinated Al (Al^V) species are identified as key surface sites for anchoring and stabilizing metal single-site catalysts; however, Al^V is rare in conventional amorphous silica-alumina (ASA). Recently, we have developed Al^V-enriched ASA, which was applied as a support for the synthesis of Pt single-site catalysts in this work. Each preparation stage and the interaction between Pt and surface Al species were explored by ¹H and ²⁷Al solid-state nuclear magnetic resonance spectroscopy, and the formation of the dominant Pt single sites on the surface of Al^V-enriched ASA was confirmed by high-angle annular dark-field imaging scanning transmission electron microscopy and energy dispersive spectroscopy line scanning. On the surface of supports without a significant Al^V population (Pt/Al₂O₃ and Pt/SiO₂), mainly Pt nanoparticles were formed. This indicates that Al^V contributes to the strong metal-support interaction to stabilize the Pt single sites on Pt/ASA, which was characterized by diffuse reflectance infrared Fourier transform spectroscopy combined with CO adsorption, X-ray photoelectron spectroscopy, and electron energy loss spectroscopy. Pt single sites supported on Al^V-enriched ASA exhibit excellent chemoselectivity in the hydrogenation of C═O groups, affording 2-3-fold higher yields compared to those of Pt nanoparticles supported on Al₂O₃ and SiO₂.