Application of Resonance Oscillation to the Design of Heterogeneous Catalysts with Artificially Controllable Functions for Chemical Reactions

射频功率作用于极化铁电晶体上的压电效应所产生的体声波共振振荡（RO）会引起金属薄膜表面的动态畸变。在C_2H_5OH和CO氧化以及C_2H_5OH在Ag和Pd催化剂上的分解过程中，发现厚度扩展模式RO （TERO）不仅能提高催化活性，而且能提高反应选择性。相比之下，厚度-剪切模式共振振荡（TSRO）没有激活效应。激光多普勒和光电发射光谱测量表明，TERO引起了金属催化剂在垂直于表面的较大晶格位移，并引起了金属催化剂的功函数位移，而TSRO没有发生这种变化。TERO对催化剂活化的影响取决于铁电基底的极化方向和共振频率，表明大的垂直晶格位移和引起晶格位移的位点密度是催化剂强活化的原因。Ag和AgAu合金催化剂在乙醇分解中的TERO效应存在本质差异。TERO诱导的活化只发生在银金属上的乙烯生产上，而TERO效应对合金成分有很强的依赖性。乙烯生产的活化几乎与合金成分无关，但乙醛生产的活化在表面Au含量约80%时达到最大值，此时垂直晶格位移最小。因此，有人提出，在Ag-Au原子相互作用变得强烈的情况下，AgAu二元合金催化剂上的TERO对乙醛生产的影响增加。反渗透对金属非均相催化反应的影响是一种新现象，对开发具有人工控制功能的非均相催化剂具有重要意义。

Resonance oscillation (RO) of bulk acoustic waves generated by piezoelectric effects on poled ferroelectric crystals by rf electric power causes the dynamic distortion of thin metal film surfaces deposited. In C_2H_5OH and CO oxidation and C_2H_5OH decomposition on Ag and Pd catalysts, thickness-extension mode RO (TERO) was found to have a capability of enhancing not only catalytic activity, but also reaction selectivity. In contrast, thickness-shear mode resonance oscillation (TSRO) showed no activation effects. Laser Doppler and photoemission spectroscopic measurements showed that TERO caused large lattice displacement vertical to the surface and to induce work function shifts of the metal catalysts, whereas no such changes occurred with TSRO. The TERO effects on catalyst activation depended on the polarization direction of ferroelectric substrates and resonance frequency, indicating that large vertical lattice displacement and the density of sites causing lattice displacement are responsible for strong catalyst activation. The TERO effects were intrinsically different in ethanol decomposition between Ag and AgAu alloy catalysts. TERO-induced activation occurred only for ethylene production on a Ag metal, whereas TERO effects had strong dependence on alloy compositions. The activation for ethylene production was nearly independent of alloy composition, but that for acetaldehyde production exhibited a maximum at around 80% surface Au content where the vertical lattice displacement became the smallest. Thus, it was proposed that the TERO effects on acetaldehyde production over the AgAu binary alloy catalysts increased in the case where Ag-Au atom interactions became strong. The RO effects on heterogeneous catalysis by metals are new phenomena and are concluded to be quite useful for the development of a heterogeneous catalyst with artificially controllable functions for chemical reactions.