Catalytic activity of Pd activated by a shear horizontal leaky surface acoustic wave generated on LiTaO3

Abstract

A shear horizontal leaky surface acoustic wave (SH-LSAW) of 20.8 MHz has been generated on a 36°-rotated Y-cut LiTaO₃ single crystal, and the effect on the catalytic activity for ethanol oxidation of 10 nm and 100 nm thick Pd catalysts deposited on the propagation path of the wave was studied. When the SH-LSAW was applied at 1 W, the catalytic activity of a 10 nm Pd film increased by a factor of 3.6, and the activation energy of the reaction decreased from 66 to 26 kJ mol^–1. For a 100 nm thick Pd catalyst, the SAW caused less activity increase with a change in the activation energy from 60 to 46 kJ mol^–1. With a pulsed SH-LSAW, acoustoluminescence was observed on a Cu-doped ZnS layer deposited on the propagation path. This indicates that a high electric field is generated on the surface on which the SH-SAW propagates. The effects of the SH-LSAW are compared with those of the Rayleigh SAW obtained previously.