我們計畫研究奈米粒子上的非侷域電子(靠近費米能級的電子)如何影響催化性質。觸媒的催化性質由觸媒表面電子結構決定，然而此電子結構由諸多互相影響的因素決定。因此，要精準地控制奈米粒子的電子結構，例如加一個或兩個電子，是很不容易的事。我們計畫研究MgO/Ag(001)和CuO/Cu(110)上鉑金(Pt)和銠(Rh)奈米粒子的催化能力，因為電子可以穿隧氧化物薄膜，於金屬基板和奈米粒子間移轉。透過控制氧化物薄膜的厚度，我們可以打開或是關閉此穿隧路徑。因為氧化物薄膜的厚度不太影響其他決定電子結構的因素，我們可以藉此研究轉移電荷單獨對催化性質的影響，進一步探討非侷域電子(靠近費米能級的電子)對催化性質的效應。我們的研究包含三個方面：催化模型系統的製備與特徵量測，表面催化反應的特徵量測，密度泛涵計算模擬。前兩項將使用各式表面探測技術與超高真空系統，後者將確認電荷轉移，並計算出在不同表面位置的活化能與反應能量，以確認轉移電荷對催化反應的影響。 ;We propose to investigate how non-localized electrons, those near fermi level, in supported nanoclusters govern catalytic properties. The catalytic properties are determined by the electronic structures of surfaces of catalysts, whereas the electronic structures are determined by many factors. These factors are not independent of each other, but strongly correlated. A precise control of the electronic structure of supported nanoclusters, such as adding one or two electrons to the nanoclusters, is not a ready job. We propose to study the reactivity of Pt and Rh nanoclusters supported on MgO/Ag(001) and CuO/Cu(110), as electrons may tunnel, via the oxide films, between the nanoclusters and metal substrates. By varying the oxides thickness, one may open or shut down the tunneling channel. As varying the oxide thickness alters little the other factors which determine surface electronic structures, this approach allows us to investigate the sole effect of the transferred charge on catalytic properties and furthermore to address the fundamental issue — the effect of non-localized electrons on catalytic properties. The scheduled investigations contain three aspects: preparation and characterization of model systems, monitoring of surface reactions and density-functional-theory simulations. The first two will be performed with various surface probe techniques under ultrahigh vacuum. The latter will confirm the charge transfer between the metal substrates and clusters, and also the effect of transferred electrons by giving the activation barrier and reaction energy for each process in reactions.
