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

极化铁电压电体暴露了正负极表面，并允许产生声表面波(SAW)。本工作以极化的LiNbO_3单晶为载体，在其上沉积了半导体氧化物(TiO_2、SnO)或金属(Pd)等催化活性相。研究了载体极化方向的静态效应和声表面波(20 MHz)的动态效应对复合催化活性相吸附和催化性能的影响。由于H_2、CO、CO_2和C_2H_4等多种气体在TiO_2/LiNbO_3和SnO/LiNbO_3上的化学吸附，表面电导率的变化明显大于负极性载体，并且随着吸附气体电离势的增加，极性载体之间的差异变大。用半导体氧化物与LiNbO_3表面接触引起的能带弯曲来解释这些极化方向的关系。结果表明，表面声表面波对少量O_2和H_2的吸附很敏感。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)等不同类型的催化反应的声表面波效应，发现在涉及极性分子的反应中，动态声表面波效应显著。

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.