LeRoy Eyring Center for Solid State Science, Arizona State University, Tempe, Arizona 85287, USA.
Key Laboratory of Bio-inspired Smart Interfacial Science and Technology of Ministry of Education, Beijing Key Laboratory of Bio-inspired Energy Materials and Devices, School of Chemistry and Environment, Beihang University, Beijing 100191, China.
Nat Commun. 2016 Jul 13;7:12251. doi: 10.1038/ncomms12251.
To probe the nature of metal-catalysed processes and to design better metal-based catalysts, atomic scale understanding of catalytic processes is highly desirable. Here we use aberration-corrected environmental transmission electron microscopy to investigate the atomic scale processes of silver-based nanoparticles, which catalyse the oxidation of multi-wall carbon nanotubes. A direct semi-quantitative estimate of the oxidized carbon atoms by silver-based nanoparticles is achieved. A mechanism similar to the Mars-van Krevelen process is invoked to explain the catalytic oxidation process. Theoretical calculations, together with the experimental data, suggest that the oxygen molecules dissociate on the surface of silver nanoparticles and diffuse through the silver nanoparticles to reach the silver/carbon interfaces and subsequently oxidize the carbon. The lattice distortion caused by oxygen concentration gradient within the silver nanoparticles provides the direct evidence for oxygen diffusion. Such direct observation of atomic scale dynamics provides an important general methodology for investigations of catalytic processes.
为了探究金属催化过程的本质并设计更好的基于金属的催化剂，非常需要从原子尺度理解催化过程。在这里，我们使用像差校正的环境透射电子显微镜来研究银基纳米粒子催化多壁碳纳米管氧化的原子尺度过程。通过银基纳米粒子直接对半定量估计被氧化的碳原子。我们提出了一个类似于 Mars-van Krevelen 过程的机制来解释催化氧化过程。理论计算结合实验数据表明，氧分子在银纳米粒子表面上解离，并通过银纳米粒子扩散到银/碳界面，随后氧化碳。银纳米粒子内氧浓度梯度引起的晶格畸变为氧扩散提供了直接证据。这种对原子尺度动力学的直接观察为催化过程的研究提供了一种重要的通用方法。
