Adsorbed states of acetone and their reactions on Rh(111) and Rh(111)-(2 times 2)O surfaces

Journal Article · Thu May 02 04:00:00 EDT 1991 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100162a059· OSTI ID:5890628

Houtman, C; Barteau, M A ^[1]

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1. Univ. of Delaware, Newark (United States)

The binding and decomposition of acetone on clean and modified Rh(111) surfaces were studied by using TPD (temperature-programmed desorption) and HREELS (high-resolution electron energy loss spectroscopy). On the clean surface the {eta}{sup 2}(C,O) configuration was the dominant form of acetone. This species was characterized by a {nu}(CO) frequency of 1,380 cm{sup {minus}1}. This value was 430 cm{sup {minus}1} below the {nu}(CO) frequency of liquid acetone, indicating a substantial reduction in bond order arising from the binding of acetone to the metal surface via the {pi} and {pi}* orbitals of the carbonyl. The strength of this interaction was also indicated by the reactivity of the {eta}{sup 2}(C,O)-acetone intermediate. All acetone molecules adsorbed in the first monolayer on the clean surface decomposed to CO, H{sub 2}, and surface carbon. This decomposition exhibited a primary kinetic isotope effect upon deuterium substitution in both TPD and HREELS experiments. Thus C-H rather than C-C scission was the rate-determining step in acetone decomposition on Rh(111). Three different methods of estimating the acetone decomposition kinetics from the hydrogen TPD were compared. Accurate modeling of the kinetics required inclusion of the effect of hydrogen atom recombination kinetics on the rate of hydrogen evolution from the surface. Modification of the surface by addition of a (2 {times} 2) overlayer of oxygen resulted in a change in the acetone binding configuration from {eta}{sup 2}(C,O) to {eta}{sup 1}(O). This shift was the result of electronic modification of the surface by the electronegative oxygen atoms.

• DOE Contract Number: FG02-84ER13290
• OSTI ID: 5890628
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 95:9; 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
ACETONE
ADSORPTION
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CLEANING
CONTROL
DATA
DECOMPOSITION
DECONTAMINATION
ELECTRON SPECTROSCOPY
ELEMENTS
ENERGY LEVELS
ENERGY-LOSS SPECTROSCOPY
EXPERIMENTAL DATA
INFORMATION
ISOTOPE EFFECTS
ISOTOPIC EXCHANGE
KETONES
KINETICS
METALS
MILLER INDICES
MOLECULAR STRUCTURE
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
OXYGEN
PLATINUM METALS
PYROLYSIS
REACTION KINETICS
RHODIUM
SORPTION
SPECTROSCOPY
SURFACE PROPERTIES
SURFACES
TEMPERATURE CONTROL
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TEMPERATURE RANGE 0065-0273 K
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENTS