Nonclassical Adsorption of Methanol on Palladium: The Competition between Adsorption of Single Molecules and Clusters

Abstract

The adsorption of methanol on the Pd(111) surface at 80, 90, and 100 K has been studied by polarization modulation infrared reflection−absorption spectroscopy. It is found that the adsorption of methanol on the palladium surface does not proceed via the layer-by-layer mechanism. At temperatures below 100 K, methanol adsorbs molecularly to form clusters containing several hydrogen-bonded CH 3 OH molecules. These clusters have low thermal stability and decompose even at 100 K to form isolated methanol molecules bonded with palladium atoms. As a result, at a temperature between 100 and 120 K, methanol adsorbs intact to produce adsorbed isolated molecules. These adsorbed species fast desorb at a temperature above 120 K. The dehydration of methanol is not observed under used conditions.

Low Temperature Multilayer Adsorption of Methanol and Ethanol on Platinum

“…4 In contrast to Galvez et al, 9 we observed the crystallization of these amorphous layers even at 100 K; moreover, at 120 K, methanol is completely desorbed from the palladium surface. 4 No adsorbed methanol species were observed at 130 K. This means that there is a size effect in the condensation and crystallization of small molecules at cryogenic temperatures, and the physical properties at least of bulk 1 Boreskov Institute of Catalysis SB RAS, Novosibirsk, Russian Federation solid methanol and a thin layer of condensed methanol differ. To elucidate this effect, we examined the multilayer adsorption of methanol and ethanol on the Pt (111) surface in a temperature range between 80 and 130 K. These molecules are of different lengths, which can affect the crystallization process.…”

“…Recently, we have studied the multilayer adsorption of methanol on palladium and found that condensation of methanol leads to the formation of an amorphous phase at 90 K only. 4 In contrast to Galvez et al, 9 we observed the crystallization of these amorphous layers even at 100 K; moreover, at 120 K, methanol is completely desorbed from the palladium surface. 4 No adsorbed methanol species were observed at 130 K. This means that there is a size effect in the condensation and crystallization of small molecules at cryogenic temperatures, and the physical properties at least of bulk 1 Boreskov Institute of Catalysis SB RAS, Novosibirsk, Russian Federation solid methanol and a thin layer of condensed methanol differ.…”

“…The rapid development of space science in recent years has initiated an increased interest in the study of molecular solids in the cryogenic temperature range. 1 The main part of the research is devoted to the study of the processes of condensation of water, methanol, and ethanol, 2–4 crystallization of amorphous substances, 4,5 and interaction of different molecules 6–8 at cryogenic temperatures. These molecular species have been detected in a wide range of astronomical locations including planetary atmospheres, atmospheres of cool stars, and dense and diffuse clouds in the interstellar medium.…”

Mechanistic Study of Selective Oxidation of Methanol over a Monolayer V2O5/CeO2 Catalyst

“…Moreover, no bands in the range of 3200− 3350 cm −1 , which are typical of the ν(OH) stretching vibrations of adsorbed molecules of methanol, are observed. 19 This means that even at 150 °C, methanol is dissociatively adsorbed on vanadia, forming methoxy groups.…”

“…The temperature was measured using a K-type thermocouple spot-welded to the back of the plate. The sample holder could be transferred between the analytical chamber and the HPC using a manipulator . Methanol and oxygen were introduced into the HPC separately by using variable leak valves.…”