Identification of surface intermediates during ethylidyne formation on Pt(111) by calculation of infrared intensities and deuterium isotope shifts

SURFACE SCIENCE

卷:640

Article

Zhao, Zhi-Jian¹  Greeley, Jeffrey P.¹ 

[1] Purdue Univ, Sch Chem Engn, W Lafayette, IN 47907 USA

关键词: Density functional theory;    Adsorption;    Hydrogenation catalysts;    Ethylidyne;    Pt(111);    Infrared spectroscopy;   

DOI  :  10.1016/j.susc.2015.01.022

来源: Elsevier

【 摘 要 】

The conversion of ethylene to ethylidyne on Pt(111) is a well-studied model reaction related to conversion of hydrocarbons over noble metal catalysts. For this chemistry, a two step mechanism that proceeds via an ethylidene intermediate has been generally accepted since the mid-1990s. However, recent DFT calculations (J. Phys Chem. C 2010, 114, 12190) have suggested that this intermediate may, in fact, be short-lived and should not be observed. Experimental verification of this prediction, though, is not straightforward, and to provide further theoretical results by which the prediction could be more easily evaluated, we present a set of benchmark calculations of infrared frequencies and intensities of candidate intermediates adsorbed on the Pt(111) surface at realistic coadsorbate coverages. The results show that only modest differences in frequencies and intensities exist between these intermediates, rendering direct spectroscopic differentiation difficult. However, by substituting the C-2 species and intermediates with deuterium, it is shown that one characteristic vibrational band of vinylidene and ethylidene can be separated by well over 100 cm(-1). This result provides a clear prediction that, if coupled with measured vibrational spectra of deuterium-labeled C-2 species, could definitively differentiate between the most likely intermediates in this reaction network. (C) 2015 Elsevier B.V. All rights reserved.

【 授权许可】

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