He jishu (Aug 2022)

Synchrotron radiation study of effects of high temperature oxidation on metal-support interactions in catalysts

  • HE Wenxue,
  • LI Hongmei,
  • CHEN Wei,
  • PAN Ya,
  • XU Liuxin,
  • SUN Zhihu,
  • WEI Shiqiang

DOI
https://doi.org/10.11889/j.0253-3219.2022.hjs.45.080101
Journal volume & issue
Vol. 45, no. 8
pp. 080101 – 080101

Abstract

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BackgroundMetal-Support Interaction (MSI) modulates the activity, stability, and selectivity of catalysts by changing the morphology, composition, and electron density of metal particles. Such interactions in supported single-atom and cluster catalysts will be subjected to changes when the catalysts are treated at different temperatures and under different atmospheres.PurposeThis study aims to explore the effects of high temperature treatment on metal-support interactions of Pt/TiO2 and Pt/SiO2 catalysts with the coexistence of single atoms and clusters when heating and calcined in air at high temperature.MethodsThe structural evolutions of these two catalysts were investigated by a combination of high-resolution transmission electron microscopy (HRTEM), aberration-corrected high-angle annular dark-field transmission electron microscopy (AC-HAADF-STEM), synchrotron radiation technique X-ray absorption fine structure spectroscopy (XAFS), diffuse reflection Fourier transform infrared spectroscopy (DRIFT). XAFS characterization was conducted at Beijing Synchrotron Radiation Facility (BSRF) 1W1B beamline station to obtain information about the valence state and coordination environment of Pt/TiO2 at different calcination temperatures to confirm that Pt mono-atoms were immobilized on the support by Covalent Metal-Support Interaction (CMSI).ResultsAfter calcination at 700 ℃, all Pt species are presented as Pt single atoms in Pt/TiO2, while they agglomerate into larger particles in Pt/SiO2. The reducibility of metal oxides determines the ability of the support for anchoring single atoms of Pt: single atoms of Pt in TiO2 can be stabilized via the CMSI, and thus facilitate the dispersion of Pt atoms. On the contrast, CMSI cannot be formed between Pt and SiO2, resulting in particle sintering at high temperatures.ConclusionsThe formation of CMSI effect between metals and supports can be used as a general method for the preparation of reducible oxide supported high-loading, thermally stable single-atom catalysts.

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