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Adsorption properties of acrolein, propanal, 2-propenol, and 1-propanol on Ag(111)
Mark Muir,David L. Molina,Arephin Islam,Mohammed K. Abdel-Rahman,Michael Trenary
Physical Chemistry Chemical Physics Pub Date : 10/19/2020 00:00:00 , DOI:10.1039/D0CP04634E
Abstract

Reflection absorption infrared spectroscopy and temperature programmed desorption were used to study the adsorption of acrolein, its partial hydrogenation products, propanal and 2-propenol, and its full hydrogenation product, 1-propanol on the Ag(111) surface. Each molecule adsorbs weakly to the surface and desorbs without reaction at temperatures below 220 K. For acrolein, the out-of plane bending modes are more intense than the C[double bond, length as m-dash]O stretch at all coverages, indicating that the molecular plane is mainly parallel to the surface. The two alcohols, 2-propenol and 1-propanol, have notably higher desorption temperatures than acrolein and display strong hydrogen bonding in the multilayers as revealed by a broadened and redshifted O–H stretch. For 1-propanol, annealing the surface to 180 K disrupts the hydrogen-bonding to produce unusally narrow peaks, including one at 1015 cm−1 with a full width at half maximum of 1.1 cm−1. This suggests that 1-propanol forms a highly orderded monolayer and adsorbs as a single conformer. For 2-propenol, hydrogen bonding in the multilayer correlates with observation of the C[double bond, length as m-dash]C stretch at 1646 cm−1, which is invisible for the monolayer. This suggests that for monolayer coverages, 2-propenol bonds with the C[double bond, length as m-dash]C bond parallel to the surface. Similarly, the C[double bond, length as m-dash]O stretch of propanal is very weak for low coverages but becomes the largest peak for the multilayer, indicating a change in orientation with coverage.

Graphical abstract: Adsorption properties of acrolein, propanal, 2-propenol, and 1-propanol on Ag(111)
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