Sn-modification of Pt7/alumina model catalysts: Suppression of carbon deposition and enhanced thermal stability

Guangjing Li; Borna Zandkarimi; Ashley C Cass; Timothy J Gorey; Bradley J Allen; Anastassia N Alexandrova; Scott L Anderson

doi:10.1063/1.5129686

Sn-modification of Pt₇/alumina model catalysts: Suppression of carbon deposition and enhanced thermal stability

J Chem Phys. 2020 Jan 14;152(2):024702. doi: 10.1063/1.5129686.

Authors

Guangjing Li¹, Borna Zandkarimi², Ashley C Cass¹, Timothy J Gorey¹, Bradley J Allen¹, Anastassia N Alexandrova², Scott L Anderson¹

Affiliations

¹ Chemistry Department, University of Utah, Salt Lake City, Utah 84112, USA.
² Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA.

PMID: 31941332
DOI: 10.1063/1.5129686

Abstract

An atomic layer deposition process is used to modify size-selected Pt₇/alumina model catalysts by Sn addition, both before and after Pt₇ cluster deposition. Surface science methods are used to probe the effects of Sn-modification on the electronic properties, reactivity, and morphology of the clusters. Sn addition, either before or after cluster deposition, is found to strongly affect the binding properties of a model alkene, ethylene, changing the number and type of binding sites, and suppressing decomposition leading to carbon deposition and poisoning of the catalyst. Density functional theory on a model system, Pt₄Sn₃/alumina, shows that the Sn and Pt atoms are mixed, forming alloy clusters with substantial electron transfer from Sn to Pt. The presence of Sn also makes all the thermally accessible structures closed shell, such that ethylene binds only by π-bonding to a single Pt atom. The Sn-modified catalysts are quite stable in repeated ethylene temperature programmed reaction experiments, suggesting that the presence of Sn also reduces the tendency of the sub-nano-clusters to undergo thermal sintering.