Molecular adsorption on V2O3(0001)/Au(111) surfaces

Abstract

The adsorption of carbon monoxide (CO), propane (C 3 H 8 ) and propene (C 3 H 6 ) on V 2 O 3 (0001) films grown on Au(111) was studied by Temperature Programmed Desorption (TPD) and X-ray Photoelectron Spectroscopy (XPS). The ''oxidized'' surface (i.e., as prepared exhibiting V=O termination), the ''reduced'' surface (i.e., V=O groups being removed by electron irradiation), as well as the oxygen pre-covered reduced surface were investigated. Both TPD and XPS indicate that the oxidized surface has little affinity for CO adsorption, while the reduced surface readily binds CO (CO amount approx. 10 times higher). Accordingly, CO can be used to titrate the presence or absence of vanadyl oxygen (via adsorption on the vanadium atoms) but also of defects like surface oxygen vacancies. For propane and propene, desorption of the parent molecules was the major process, i.e., surface reactions were absent under the applied conditions. When oxygen was pre-adsorbed on the reduced surface, the adsorption properties resembled that of the oxidized surface, i.e., the vanadyl groups were (partially) re-established. TPD and XPS provide a handle to differentiate the binding sites on the V 2 O 3 surface.

Ultrathin Oxide Films on Au(111) Substrates

“…STM allows identification of the active sites and research has been conducted into methods for improving the catalytic activity. For example, oxygen vacancies serve as the absorption sites for CO, propane and propene molecules on V 2 O 3 (0001) and V 2 O 5 (001) films on Au(111), which can be created by electron irritation of the surface to promote a variety of reactions [51,70,71]. CO oxidation that may take place at the Fe 2 O 3 /Au and titania/Au perimeter interface can be enhanced by optimization of the coverage of Fe 2 O 3 or TiO x [16,17].…”

Relating methanol oxidation to the structure of ceria-supported vanadia monolayer catalysts

“…To elucidate the ODH reaction mechanism over vanadia on a molecular level, different model systems have been invoked that range from single crystals [22,23] and thin films prepared on TiO 2 [24][25][26], W(110) [27] , Au(111) [27][28][29][30][31] , Rh(111) [32][33][34] , and Cu 3 Au(100) [35][36][37] to vanadia particles deposited onto oxide substrates [21,38,39] including ceria [40][41][42]. In addition to experimental investigations, density functional theory h as been employed to explore the structural characteristics and reactivity towards methanol of model vanadia systems [43][44][45][46][47][48].…”

Properties of oxide thin films and their adsorption behavior studied by scanning tunneling microscopy and conductance spectroscopy

“…In contrast, the V=O vacancy sites turned out to be non-reactive for these two and similar molecular adsorbates. 442 The final topic of this paragraph concerns the adsorption characteristics of step edges and line defects in thin oxide films. The outstanding role of surface steps for the nucleation and growth of metal particles has been realized already at the very beginning of STM experiments on oxide surfaces.…”