Acoustic surface lattice vibration by resonance oscillation and its effects on the selectivity of ethanol decomposition over a thin Pd film catalyst surface

The effects of acoustic surface lattice vibration on the reaction selectivity of ethanol decomposition over a thin Pd film deposited on a positive polar ferroelectric LiNbO3 substrate were studied. Ethanol decomposition on the Pd surface produced ethylene as dehydration and acetaldehyde as dehydrogenation. The artificially forced acoustic lattice vibration due to thickness-extensional mode resonance oscillation increased ethylene production remarkably but little enhancement of acetaldehyde production: the selectivity for ethylene production was increased significantly. Three-dimensional laser Doppler measurements showed standing wave patterns, indicating that acoustic lattice vibration had large lattice displacement vertical to the surface: its amplitude reached 43 nm at 2 W. In photoelectron emission spectra, acoustic lattice vibration increased the threshold energy of electron emission from the Pd surface, which indicated an increase in a work function-relating factor. A model for the effects of acoustic surface lattice vibration is proposed.