Spectroscopic Identification of Surface Intermediates in the Dehydrogenation of Ethylamine on Pt(111)

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 (CH3CH2NH2) 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 (CCHNH2), a stable surface intermediate that partially desorbs as acetonitrile (CH3CN) at 340-360 K. DFT simulations using various surface models confirm the structure of aminovinylidene. Upon annealing to 420 K, undesorbed aminovinyliclene 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 CCNH2, 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.