Adsorption and Decomposition of Monoethanolamine on Cu(100)

Abstract

Temperature-programmed reaction/desorption and reflection−absorption infrared spectroscopy have been employed to investigate the adsorption and decomposition of HOCH2CH2NH2 on Cu(100). HOCH2CH2NH2 molecules desorb from the multilayer and monolayer with a maximum rate at 203 and 255 K, respectively. The desorption state at 255 K corresponds to an adsorption energy of 66.0 kJ·mol−1 calculated for a first-order kinetics with a preexponential factor of 1013 s−1. RAIRS suggests that the multilayer and monolayer may be composed of different HOCH2CH2NH2 rotational isomers. HOCH2CH2NH2 can also decompose on Cu(100), approximately at the same temperature range of monolayer desorption, mainly to evolve H2 and H2O at ∼400 K. An Ar+-sputtered Cu(100) surface is found to promote the dissociation of HOCH2CH2NH2. Temperature-dependent RAIRS, with the assistance of theoretical calculations based on density-functional theory, strongly suggests that HOCH2CH2NH2 on Cu(100) dissociates first by losing a hydrogen atom to form −OCH2CH2NH2, followed by transformation into HOCH2CH2N═. Decomposition of the latter species is responsible for the desorption of H2 and H2O.