Activation of a thin film Pd catalyst for CO and ethanol oxidation by surface acoustic waves

The effects of surface acoustic waves (SAW) on the activity of an oxidized and reduced Pd thin film catalyst, deposited as a thin film on the propagation path, were examined for CO and ethanol oxidation, A 19.4 MHz Rayleigh SAW generated on a 128 degrees Y-cut LiNbO3 single crystal caused not only higher activity enhancement but also larger changes in the activation energy and reaction orders for CO oxidation over the oxidized than over the reduced Pd surface. The larger SAW effects on the oxidized Pd surface were also observed for ethanol oxidation. The SAW has been shown to have a significant effect on the strongly adsorbed species, The difference in the SAW effects between the oxidized and reduced Pd is explained on the basis of the difference in the contribution of SAW-induced lattice displacement, an electric field and a sonic wave-electron interaction.