Spectroscopic Identification of Surface Intermediates
in the Dehydrogenation of Ethylamine on Pt(111)
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Abstract
Reflection absorption infrared spectroscopy,
temperature-programmed
desorption, and density functional theory (DFT) have been used to
study the surface chemistry and thermal decomposition of ethylamine
(CH<sub>3</sub>CH<sub>2</sub>NH<sub>2</sub>) on Pt(111). Ethylamine
adsorbs molecularly at 85 K, is stable up to 300 K, and is partially
dehydrogenated at 330 K to form aminovinylidene (CCHNH<sub>2</sub>), a stable surface intermediate that partially desorbs as acetonitrile
(CH<sub>3</sub>CN) at 340–360 K. DFT simulations using various
surface models confirm the structure of aminovinylidene. Upon annealing
to 420 K, undesorbed aminovinylidene undergoes further dehydrogenation
that results in the scission of the remaining C–H bond and
the formation of a second surface intermediate called aminoethynyl
with the structure CCNH<sub>2</sub>, bonded to the surface through
both C atoms. The assignment of this intermediate species is supported
by comparison between experimental and simulated spectra of the isotopically
labeled species. Further annealing to temperatures above 500 K shows
that the C–N bond remains intact as the desorption of HCN is
observed