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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Revisiting the Au Particle Size Effect on TiO2-Coated Au/TiO2 Catalysts in CO Oxidation Reaction
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Revisiting the Au Particle Size Effect on TiO2-Coated Au/TiO2 Catalysts in CO Oxidation Reaction

机译：考察CO氧化反应中Au粒径对TiO2包覆Au / TiO2催化剂的影响

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It is well-known that the particle size of Au nanoparticles enormously affects the catalytic activity of supported gold catalysts in many reactions. The origin of the Au particle size effect is still widely debated. In this work, we precisely deposited different thicknesses of ultrathin TiO2 overcoats onto three Au/TiO2 catalysts with Au particle sizes of 2.9 +/- 0.6 (Au/TiO2-S), 5.0 +/- 0.8 nm (Au/TiO2-M), and 10.2 +/- 1.6 nm (Au/TiO2-L) using atomic layer deposition (ALD). High-resolution transmission electron microscopy illustrated the Au nanoparticles on these three samples were encapsulated by the TiO2 overcoat. X-ray photoelectron spectroscopy measurements showed that the Au nanoparticles remained at metallic state after applying TiO2 ALD overcoat. Diffuse reflectance infrared Fourier transform spectroscopy measurements of CO chemisorption further revealed that the TiO2 overcoat preferentially decorated at the low-coordination sites of Au nanoparticles and broadly tuned the population of these sites accessible for participating in reactions. In CO oxidation reaction, the TiO2 coated Au/TiO2-S catalysts strikingly demonstrated considerably higher activities than the uncoated Au/TiO2-M and Au/TiO2-L catalysts, even though the former ones contained significantly less amount of CO adsorption sites due to the TiO2 overcoating. Our work shows direct evidence that CO adsorption on the low-coordination Au sites is not the rate-determining step, and the Au particle size effect in CO oxidation is NOT related with either the number of the low-coordination Au sites or the changes in oxidation states. Size-related change in the length of perimeter sites at the Au-TiO2 interface could certainly play a role in the Au particle size effect.
机译：众所周知，在许多反应中，金纳米颗粒的粒径极大地影响了负载型金催化剂的催化活性。 Au粒径效应的起源仍被广泛争论。在这项工作中，我们精确地将不同厚度的超薄TiO2涂层沉积到三种Au尺寸为2.9 +/- 0.6（Au / TiO2-S），5.0 +/- 0.8 nm（Au / TiO2-M）的Au / TiO2催化剂上，并使用原子层沉积（ALD）制成10.2 +/- 1.6 nm（Au / TiO2-L）。高分辨率透射电子显微镜显示这三个样品上的Au纳米颗粒被TiO2涂层包裹。 X射线光电子能谱测量表明，金纳米粒子在应用TiO2 ALD外涂层后仍保持金属状态。 CO化学吸附的漫反射红外傅里叶变换光谱测量进一步揭示，TiO2涂层优先装饰在Au纳米颗粒的低配位位点上，并广泛调节了可参与反应的这些位点的数量。在CO氧化反应中，TiO2包覆的Au / TiO2-S催化剂比未包覆的Au / TiO2-M和Au / TiO2-L催化剂具有显着更高的活性，尽管前者由于TiO2外涂层。我们的工作表明直接证据表明，CO在低配位Au位上的吸附不是决定速率的步骤，CO氧化中的Au粒度效应与低配位Au位的数量或C的变化无关。氧化态。在Au-TiO2界面的周边位置长度的尺寸相关变化当然可以在Au粒径效应中起作用。

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