The surface characterization of a series of hydroxybenzenes on Ag(111): an EELS and TDS study

Abstract

<p>The interaction of a series of hydroxybenzenes with Ag(111) is investigated by thermal desorption spectroscopy (TDS) and high resolution electron energy loss spectroscopy (EELS) in an effort to model how technologically important phenolic resins interact with metal surfaces. We examine how the number and position of hydroxyl substituents on a benzene ring affect the bonding geometry and reactivity of the molecule with the metal surface;The molecules studied in this work include the mono-hydroxybenzene, phenol, the o-, m- and p-dihydroxybenzenes, catechol, resorcinol, hydroquinone, respectively, and the 1,2.3-trihydroxybenzene, pyrogallol. All of the hydroxybenzene molecules undergo associative adsorption and molecular desorption, indicating that the molecules retain their aromaticity upon adsorption;Dehydrogenation of the hydroxyl groups upon adsorption is not directly observed in the TDS studies; however, the EELS results suggest possible dehydrogenation. The apparent O-H bond scission is attributed to hydrogen bonding between the surface molecules or to the orientation of the O-H bond axis with respect to the metal surface;The orientations of the mono- and dihydroxybenzene molecules are temperature dependent, whereas that of the trihydroxybenzene appears not to depend on temperature. The temperature dependence may be attributed to the number and position of the hydroxyl substituents. Phenol and catechol both undergo an inclined-to-perpendicular orientational change. Resorcinol and hydroquinone undergo a perpendicular-to-inclined transformation. Finally, pyrogallol remains inclined at all temperatures until decomposition;Fundamental research on the interaction of hydroxybenzenes with metal surfaces, such as that described here, may potentially improve the related industrially important phenolic resins.</p>