AVS 50th International Symposium
    Surface Science Wednesday Sessions
       Session SS-WeP

Paper SS-WeP10
Effects of Thickness Extension Resonance Oscillation of Acoustic Wave on Activity/Selectivity of Metal Catalysts with Two Layer Structures

Wednesday, November 5, 2003, 11:00 am, Room Hall A-C

Session: Poster Session
Presenter: Y. Oka, Nagaoka University of Technology, Japan
Authors: Y. Oka, Nagaoka University of Technology, Japan
Y. Nakajima, Nagaoka University of Technology, Japan
N. Saito, Nagaoka University of Technology, Japan
H. Nishiyama, Nagaoka University of Technology, Japan
Y. Inoue, Nagaoka University of Technology, Japan
Correspondent: Click to Email
We have so far reported that the thickness-extension resonance oscillation (TERO) of acoustic wave generated on a ferroelectric crystal by a piezoelectric effect has the ability to markedly enhance the catalytic activity and to significantly change the reaction selectivity of metal-catalyzed reactions. The catalyst activation by TERO was associated with large and dynamic lattice displacement vertical to the catalyst surfaces. The TERO effects were different among the metal catalysts. In aiming at raising the efficiency of the TERO effects, it is of interest to examine the TERO effects on two-layer structure catalysts combining the different kinds of metal phases. In the present study, a metal catalyst combining Mo with Ag was employed. A ferroelectric z-cut LiNbO@sub 3@ single crystal was used as substrate, on which Ag film was deposited at a thickness of 100 nm, followed by the deposition of Mo with different thickness in the range 20- 100 nm. Auger electron spectroscopic measurements showed that the two-layer structures were maintained during catalytic run. In ethanol decomposition on the Mo/Ag catalysts with different thickness of Mo layer, major gas phase products were ethylene and acetaldehyde. With turning TERO on, only the activity for ethylene production remarkably increased. The activation coefficient, defined as the ratio of the activity with TERO-on to that with TERO-off was 16 for 100nm, 17 for 75 nm, 24 for 50 nm, and 27 for 20 nm Mo layer, indicating that the TERO-inducing activation for ethylene production became larger as the thickness of Mo layer was smaller. Lattice displacement of Mo/Ag catalysts increased with decreasing thickness of the Mo layer. There was a correlation between the extent of lattice displacement and catalyst activation by the TERO in the two layer structures. These results have demonstrated that the combination of different metal phases is useful for extending TERO effects to catalyst activation.