Journal of Physical Chemistry B, Vol.106, No.25, 6538-6542, 2002
Extraordinary lattice displacement by pulse thickness extension mode resonance oscillation of acoustic wave and its effect on the activity for ethanol oxidation of a thin Pd film catalyst
Pulse radio frequency (rf) electric power was applied to a ferroelectric single crystal of z-cut LiNbO3 to generate pulse thickness extension mode resonance oscillation (p-TERO) of bulk acoustic wave, and the effects of p-TERO on the catalytic activity for ethanol oxidation of a Pd catalyst deposited on the crystal were studied. The employment of the pulse method made it possible to introduce several times larger rf power to the catalyst, compared to conventional continuous rf power introduction. The p-TERO remarkably increased catalytic activity for acetaldehyde production, and its effects were particularly great in a high rf power region. A laser Doppler method was developed to monitor lattice displacement caused by p-TERO. The patterns of lattice displacement became nonuniform in a high rf power region by the appearance of extraordinary lattice displacement. Very large activity increases in the region were associated with the lattice displacement. The mechanism of catalyst activation by p-TERO is discussed.