Chemisorption and thermal decomposition of benzene on Pd(110): High-resolution electron energy loss spectroscopy, low-energy electron diffraction, and thermal desorption studies

Journal Article · Thu Sep 19 04:00:00 EDT 1991 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100172a056· OSTI ID:5157480

Fujisawa, M; Sekitani, T; Morikawa, Y; Nishijima, M ^[1]

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1. Kyoto Univ. (Japan)

The adsorbed state of benzene on Pd(110) at 300 K and its thermal decomposition process in the temperature region up to 700 K have been investigated by using high-resolution electron energy loss spectroscopy, low-energy electron diffraction, and multiplexed thermal desorption spectroscopy. Vibrational spectra show the existence of two adsorbed states of benzene on Pd(110) at 300 K. In one state, benzene is adsorbed with its C ring nearly parallel to the surface (flat benzene), and in the other state, at some angle (tilted benzene). The tilted benzene is located in the c(4{times}2) domains. For a small exposure ({approx lt}0.3 langmuir; fractional coverage {theta}{sub C{sub 6}H{sub 6}}{approx lt}0.07), the flat benzene predominates. With increasing exposure, conversion from flat to tilted benzene occurs, and the amount of tilted benzene is increased relative to that of flat benzene. For the saturation exposure (3 langmuirs: {theta}{sub C{sub 6}H{sub 6}} {approximately} 0.27), the tilted benzene predominates; the flat benzene also exists. Thermal decomposition of benzene on Pd(110) has been studied in detail. For a small exposure (0.3 langmuir), heating to 380-600 K forms the C{sub x}H{sub y}(x {ge} 1, y = 0,1) species as the decomposition products. By heating the sample to 600 K, they find only C adatoms exist on Pd(110). For the saturation exposure (3 langmuirs), by heating the sample to 400 K, they find the C(4{times}2) structure is well developed and the Pd(110) surface is mostly covered by tilted benzene. Heating to 400-650 K forms the C{sub x}H{sub y} (x = 1 or {ge} 3, y = 0,1) species. The decomposition temperature is shifted toward higher temperatures by the site-blocking effect of benzene admolecules themselves. The decomposition is accompanied by h{sub 2} desorption.

• OSTI ID: 5157480
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 95:19; ISSN 0022-3654; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
AROMATICS
BENZENE
CHEMICAL REACTIONS
CHEMISORPTION
DECOMPOSITION
DESORPTION
ELECTRON SPECTROSCOPY
ELEMENTS
ENERGY LEVELS
ENERGY-LOSS SPECTROSCOPY
EXCITED STATES
HYDROCARBONS
METALS
MILLER INDICES
MOLECULAR STRUCTURE
ORGANIC COMPOUNDS
PALLADIUM
PLATINUM METALS
PYROLYSIS
SEPARATION PROCESSES
SORPTION
SORPTIVE PROPERTIES
SPECTROSCOPY
SURFACE PROPERTIES
SURFACES
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENTS
VIBRATIONAL STATES