Effect of shear horizontal leaky surface acoustic wave on selectivity for ethanol decomposition of a copper thin-film catalyst deposited on a positively polarized ferroelectric LiTaO3 single crystal

The effect of dynamic surface lattice vibration on the selectivity of ethan ol decomposition over a thin-film copper catalyst was studied by using a sh ear horizontal leaky surface acoustic wave (SH-LSAW) generated by radio fre quency (RF) power on a positively polarized, 36 degrees rotated, y-cut LiTa O3 single crystal. The surface acoustic wave (SAW) caused a remarkably high enhancement of ethylene production but a small increase in acetaldehyde pr oduction, thus indicating the SAW's ability to dramatically change the sele ctivity. Laser Doppler measurements showed an irregular pattern of standing waves with different amplitudes up to 5 nm during SAW propagation. Contact potential difference measurements showed the generation of a negative volt age by the SAW propagation on the positively polarized ferroelectric surfac e. These changes are quite similar to those previously observed for a thick ness-extensional mode resonance oscillation and are associated with the cha racteristic features of a leaky wave. Selective production of ethylene by t he SAW is proposed to be related to the enhancement of the copper surface-o xygen atom interactions through dynamic lattice displacement. (C) 1999 Else vier Science B.V. All rights reserved.