Effects of Thickness Extension Mode Resonance Oscillation of Acoustic Waves on Catalytic and Surface Properties. 5. Effects of Ferroelectric Crystal Thickness on the Catalytic Behavior of Ag for Ethanol Decomposition

The five kinds of ferroelectric z-cut LiNbO3 crystals with different thicknesses of 0.3, 0.5, 1.0, 2.0, and 2.2 mm were employed to reveal the effects of frequency in thickness extension mode resonance oscillation (TERO) of acoustic waves on the catalytic properties of a 100 nm thick Ag film deposited onto the crystals. The different thicknesses of the crystals provided 11.2, 7.3, 3.6, 1.8, and 1.6 MHz as the primary resonance frequency, respectively. In ethanol decomposition producing ethylene and acetaldehyde, the characteristics of the TERO that caused significant increases in catalytic activity for ethylene production were observed for the five frequencies, but the extent of activity increments depended on the frequency:  a maximum appeared at a medium frequency of 7.3 MHz. Remarkably large decreases in the activation energy for ethylene production occurred with 1.6−1.8 MHz, compared to those of the rest of the frequencies. Laser Doppler measurements showed the different distributions of lattice displ...