Insight by In Situ Gas Electron Microscopy on the Thermal Behaviour and Surface Reactivity of Cobalt Nanoparticles,ChemCatChem

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Insight by In Situ Gas Electron Microscopy on the Thermal Behaviour and Surface Reactivity of Cobalt Nanoparticles
ChemCatChem ( IF 3.8 ) Pub Date : 2018-07-24 , DOI: 10.1002/cctc.201800854
Kassiogé Dembélé _{1,

2} , Mounib Bahri ₁ , Georgian Melinte ₁ , Charles Hirlimann ₁ , Adrien Berliet ₂ , Sylvie Maury ₂ , Anne-Sophie Gay ₂ , Ovidiu Ersen _{1,

3,

4}

Affiliation

Here the thermal behaviour and the surface reactivity of cobalt catalysts supported by alumina‐silica and promoted by platinum were investigated by in situ transmission electron microscopy (in situ TEM) in a syngas environment. At the standard operating temperature of 220 °C, atomic diffusion and sintering processes onto the support are quite limited on the time scale of the TEM experiment. At temperatures between 350 and 450 °C, particles encapsulation occurred due to a higher CO dissociation and conversion into graphitic layers. Beyond 500 °C, carbon nanotubes (CNTs) growth is activated and the particles undergo (i) morphological changes through continuous elongation and contraction; and (ii) microstructural changes with the appearance of cobalt carbide. By comparing reactions under pure CO and a mixture CO−H₂, it was shown that the addition of dihydrogen to CO increased the rate of CNTs growth and modified the structure of the nanotubes. These results clearly demonstrate the strong ability of the in situ TEM to provide the main lines of the reactivity synopsis of nanocatalysts at a nanometric scale under temperature and reactive gas.

中文翻译：

原位气体电子显微镜对钴纳米颗粒的热行为和表面反应性的认识

在这里通过原位研究了由氧化铝-二氧化硅负载并由铂促进的钴催化剂的热行为和表面反应性。合成气环境中的透射电子显微镜（原位TEM）。在220°C的标准操作温度下，在TEM实验的时间范围内，原子扩散和烧结到支撑体上的过程受到很大限制。在350至450°C的温度下，由于更高的CO解离和转化成石墨层而发生了颗粒封装。超过500°C，碳纳米管（CNTs）的生长被激活，并且颗粒经历（i）通过连续的伸长和收缩而发生形态变化；（ii）微观结构随着碳化钴的出现而变化。通过比较纯CO和混合CO-H ₂下的反应，表明向CO中添加二氢增加了CNT的生长速率并改变了纳米管的结构。这些结果清楚地证明了原位TEM在温度和反应性气体下以纳米尺度提供纳米催化剂的反应概要的主要能力。

更新日期：2018-07-24

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