THE INFLUENCE OF TEMPERATURE AND SURFACE-COMPOSITION UPON THE COORDINATION OF ACETONE TO THE PD(111) SURFACE
Academic Article
Overview
Identity
Additional Document Info
Other
View All
Overview
abstract
The adsorption and reaction of (CH3)2CO and (CD3)2CO were examined on both clean and oxygen-dosed Pd(111) surfaces using HREELS and TPD. On the clean surface acetone was initially adsorbed into a slightly disordered phase that rearranged into 1-acetone ("end-on coordination") and 2-acetone ("side-on coordination") species upon heating to 200 K. These two acetone adsorption configurations were identified by their vibrational spectra. Both HREELS and TPD demonstrated that acetone adsorbed in the 1 configuration interacted weakly with the Pd(111) surface. These species either desorbed at 200 K without reacting or converted to 2-acetone during annealing the adiayer. In contrast, the interaction between the palladium surface and 2-acetone species was stronger than observed for 1 species. The higher surface-ad-sorbate bond strengths of 2-acetone resulted in competitive desorption and decomposition pathways for these species. On the oxygen-dosed Pd(111) surface, acetone adsorbed preferentially in the 1 configuration due to electronic factors arising from the increased Lewis acidity of this surface. The sequence of reactions involved in acetone decomposition is discussed along with the factors influencing the coordination of acetone in the 1 and 2 configurations. These results are compared with previous studies of acetone adsorption on the Ru(001) and Pt(111) surfaces, and serve to illuminate the influence of the surf ace-adsorbate bond upon the selectivity of acetone reactions on surfaces of Group VIII metals. 1989.
