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Sub-nanometer-thick Al2O3 Overcoat Remarkably Enhancing Thermal Stability of Supported Gold Catalysts
Chun-lei Wang,Jun-ling Lu
Author NameAffiliationE-mail
Chun-lei Wang Department of Chemical Physics, Hefei National Laboratory for Physical Sciences at the Microscale, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), CAS Key Laboratory of Materials for Energy Conversion, University of Science and Technology of China, Hefei 230026, China  
Jun-ling Lu Department of Chemical Physics, Hefei National Laboratory for Physical Sciences at the Microscale, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), CAS Key Laboratory of Materials for Energy Conversion, University of Science and Technology of China, Hefei 230026, China junling@ustc.edu.cn 
Abstract:
Supported gold nanoparticle catalysts show extraordinarily high activity in many reactions. While the relative poor thermal stability of Au nanoparticles against sintering at elevated temperatures severely limits their practical applications. Here atomic layer deposition (ALD) of TiO2 and Al2O3 was performed to deposit an Au/TiO2 catalyst with precise thickness con-trol, and the thermal stability was investigated. We surprisingly found that sub-nanometer-thick Al2O3 overcoat can su ciently inhibit the aggregation of Au particles up to 600 C in oxygen. On the other hand, the enhancement of Au nanoparticle stability by TiO2 overcoat is very limited. Di use reffectance infrared Fourier transform spectroscopy (DRIFTS) of CO chemisorption and X-ray photoelectron spectroscopy measurements both con rmed the ALD overcoat on Au particles surface and suggested that the presence of TiO2 and Al2O3 ALD overcoat on Au nanoparticles does not considerably change the electronic properties of Au nanoparticles. The catalytic activities of the Al2O3 overcoated Au/TiO2 catalysts in CO oxidation increased as increasing calcination temperature, which suggests that the embed-ded Au nanoparticles become more accessible for catalytic function after high temperature treatment, consistent with our DRIFTS CO chemisorption results.
Key words:  Au/TiO2  Sintering  Atomic layer deposition  Al2O3 overcoat  Nanoparticle stability
FundProject:
亚纳米厚的氧化铝包裹层可以显著提高负载型金纳米颗粒催化剂的热稳定性
王春雷,路军岭
摘要:
负载型金纳米颗粒催化剂在许多催化反应中展现出非常好的催化活性,但是金纳米颗粒在高温等反应条件下容易烧结团聚,极大地限制了金催化剂的应用。利用原子层沉积技术在Au/TiO2催化剂表面分别精确沉积了一层超薄的二氧化钛和氧化铝包裹层,并对比研究了包裹层对金纳米颗粒的热稳定性影响。原位红外漫反射CO吸附和x-射线光电子能谱数据证实了氧化物包裹层的存在。发现亚纳米厚的氧化铝包裹层能够在600 C完全避免金纳米颗粒的团聚;相反,二氧化钛包裹层对金纳米颗粒稳定性的提高没有明显效果。通过CO氧化探针反应的活性测试,发现随着煅烧温度的升高氧化铝包裹的Au/TiO2 催化剂的活性逐渐提高,表明高温处理可以促进被包裹金原子的暴露并表现出催化活性。提供了提高金纳米颗粒稳定性的有效方法,为拓展金催化剂在条件苛刻的反应中的应用奠定了技术基础.
关键词:  Au/TiO2  烧结  原子层沉积  氧化铝包裹  颗粒稳定性
DOI:10.1063/1674-0068/29/cjcp1604065
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