Structure sensitivity and selectivity of proton abstraction from alkynes on the polar faces of zinc oxide

Journal Article · Thu Aug 27 00:00:00 EDT 1987 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100302a025· OSTI ID:6043341

Vohs, J M; Barteau, M A

The terminal alkynes, C/sub 2/H/sub 2/, CH/sub 3/CCH, and C/sub 6/H/sub 5/CCH, decomposed on the (0001)-Zn polar face of ZnO, but not on the (0001)-O polar face. These alkynes were ultimately dehydrogenated on the (0001)-Zn polar face to produce water and to deposit carbon atoms on the surface. Adsorbed carbon was oxidized by lattice oxygen by lattice oxygen during TPD experiments, giving rise to CO and CO/sub 2/ desorption peaks at 780 K. Carbon oxidation was also found to be accompanied by zinc metal evolution. In contrast to the (0001)-Zn face, the (0001)-O face was found to be inactive for dehydrogenation of alkynes, and XPS results indicated that the alkynes did not adsorb dissociatively on this surface. Acetylene and phenylacetylene formed the corresponding acetylide species via dissociative adsorption on the active Zn-polar face. Methylacetylene adsorbed dissociatively on the (0001)-Zn polar face via abstraction of a methyl proton to form stable propargyl species exclusively. This result contrasts with the selectivity of proton abstraction both in the gas phase and on Ag(110), for which abstraction of the acetylenic proton is preferred. These results suggest that covalent contributions to the surface-adsorbate bond on ZnO may play a significant role in determining the selectivity of acid-base reactions on the (0001)-Zn surface.

• Research Organization: Univ. of Delaware, Newark
• OSTI ID: 6043341
• Journal Information: J. Phys. Chem.; (United States), Vol. 91:18
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALKYNES
DECOMPOSITION
DEHYDROGENATION
CATALYSIS
ZINC OXIDES
CATALYTIC EFFECTS
SURFACE PROPERTIES
BASES
CATALYSTS
EXPERIMENTAL DATA
INORGANIC ACIDS
CHALCOGENIDES
CHEMICAL REACTIONS
DATA
HYDROCARBONS
HYDROGEN COMPOUNDS
INFORMATION
NUMERICAL DATA
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
ZINC COMPOUNDS
400201* - Chemical & Physicochemical Properties