Abstract
The effects of surface acoustic waves (SAWs) and resonance oscillations (ROs) on the activity and selectivity of heterogeneous catalysts were reviewed. In ethanol oxidation over a Pd thin film deposited on the SAW propagation path, the SAW effects were greater for thicker Pd films and for oxidized surfaces than for metallic ones. Lattice displacement measurements and SAW propagation loss showed that the SAW effects of the oxidized catalyst surface are attributed to the interactions between electrons in the oxide layers and SAW. In RO of a poled ferroelectric Sr-doped lead zirconium titanate, the effects of a thickness extensional mode on ethanol oxidation over a Ag catalyst were associated with changes in surface potential and work functions of the Ag surface with RO. RO using a ferroelectric LiNbO3 single crystal caused a remarkably higher activity enhancement for ethanol oxidation on Pd and a selectivity change leading to higher ethylene production in the dehydration and dehydrogenation of ethanol on WO3. The SAWs and ROs are concluded to be useful for the design of a heterogeneous catalyst which has artificially controllable functions for chemical reactions.
