Static and Dynamic Effects of Ferroelectric Piezoelectrics upon Adsorptive Catalytic Properties of Combined Thin Metal and Semiconducting Oxide Films.

一种极化铁电压电材料暴露了正极和负极表面，并允许产生表面声波（SAW）。本研究采用铌酸锂（LinbO_3）单晶作为载体，在其上沉积半导体氧化物（TiO_2,SnO）或金属（Pd）等催化活性相。研究了载体极化方向对复合催化活性相吸附和催化性能的静态影响以及20 MHz声表面波对复合催化活性相吸附和催化性能的动态影响。不同气体（H_2、CO、CO_2、C_2H_4）在TiO_2/LiNbO_3和SnO/LiNbO_3上的化学吸附引起的表面电导率变化，正极性载体明显大于负极性载体，且随着吸附气体电离势的增大，极性载体之间的差异也越来越大。这些极性方向依赖性是由半导体氧化物与LinbO_3表面接触引起的能带弯曲来解释的。对于钯沉积的SAW催化剂，发现SAW的强度对少量O_2和H_2的吸附非常敏感。考察了氧化（CO+O_2, H_2+ O_2）、分解（CH_3OH, CH_3OH +O_2）和加氢（C_2H_4+H_2）等不同催化反应的声呐效应，发现极性分子反应的声呐效应显著。

A poled ferroelectric piezoelectrics exposes the positive and negative polar suraces and permits the generation of surface acoustic wave(SAW). In the present work, a poled single crystal of lithium niobate(LinbO_3) was employed as support on which catalytically active phases such as semiconducting oxides(TiO_2,SnO) or metal(Pd) were deposited as thin layers. The static effects of polarization-direction of the support as well as the dynamic effects due to SAW(20 MHz) upon the adsorptive and catalytic properties of the combined catalytically active phases were studied. The changes in surface conductivity due to the chemisorption of various gases such as H_2,CO,CO_2 and C_2H_4 on TiO_2/LiNbO_3 and SnO/LiNbO_3 were markedly greater than for the positive polar support than for the negative polar one, and the differences between the polar supports became larger with increasing ionization potential of the adsorbed gases. These polar direction-dependences were accounted for in terms of band bending caused in the semiconducting oxides by contact with LinbO_3 surface. For the Pddeposited SAW catalysts, the intensity of SAW was found to be sensitive to the adsorption of small amounts of O_2 and H_2. The SAW effects were examined for different kinds of catalytic reactions such as oxidation (CO+O_2, H_2+o_2), decomposition (CH_3OH, CH_3 OH+O_2) and hydrogenation (C_2H_4+H_2), and it was observed that the dynamic SAW effects were prominent for the reactions involving polar molecules.