Iron Carbidization on Thin-Film Silica and Silicon: A Near-Ambient-Pressure X-ray Photoelectron Spectroscopy and Scanning Tunneling Microscopy Study,ACS Catalysis

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Iron Carbidization on Thin-Film Silica and Silicon: A Near-Ambient-Pressure X-ray Photoelectron Spectroscopy and Scanning Tunneling Microscopy Study
ACS Catalysis ( IF 11.3 ) Pub Date : 2018-06-28 00:00:00 , DOI: 10.1021/acscatal.8b02076
Xiong Zhou _{1,

2} , Gilbère J. A. Mannie ₁ , Junqing Yin ₁ , Xin Yu _{1,

2} , C. J. Weststrate ₃ , Xiaodong Wen _{1,

2} , Kai Wu ₄ , Yong Yang _{1,

2} , Yongwang Li _{1,

2} , J. W. Niemantsverdriet _{1,

3}

Affiliation

Model catalysts consisting of iron particles with similar size deposited on thin-film silica (Fe/SiO₂) and on silicon (Fe/Si) were used to study iron carbidization in a CO atmosphere using in situ near-ambient-pressure X-ray photoelectron spectroscopy. Significant differences were observed for CO adsorption, CO dissociation, and iron carbidization when the support was changed from thin-film silica to silicon. Stronger adsorption of CO on Fe/Si than that on Fe/SiO₂ was evident from the higher CO equilibrium coverage found at a given temperature in the presence of 1 mbar of CO gas. On thin-film silica, iron starts to carbidize at 150 °C, while the onset of carbidization is at 100 °C on the silicon support. The main reason for the different onset temperature for carbidization is the efficiency of removal of oxygen species after CO dissociation. On thin-film silica, oxygen species formed by CO dissociation block the iron surface until ∼150 °C, when CO₂ formation removes surface oxygen. Instead, on the silicon support, oxygen species readily spill over to the silicon. As a consequence, oxygen removal is not rate-limiting anymore and carbidization of iron can proceed at a lower temperature.

中文翻译：

薄膜二氧化硅和硅上的铁碳化：近环境压力X射线光电子能谱和扫描隧道显微镜研究

模型催化剂由沉积在薄膜二氧化硅（Fe / SiO ₂）和硅（Fe / Si）上的具有相似尺寸的铁颗粒组成，用于通过原位近环境X射线研究CO气氛中的铁碳化作用光电子能谱。当载体从薄膜二氧化硅变为硅时，观察到CO吸附，CO解离和铁碳化的显着差异。与Fe / SiO ₂相比，CO在Fe / Si上的吸附更强从在1 mbar CO气体存在下在给定温度下发现的较高的CO平衡覆盖率可以明显看出这一点。在薄膜二氧化硅上，铁在150°C时开始发生碳化，而硅载体上的碳化开始于100°C。碳化起始温度不同的主要原因是一氧化碳解离后去除氧的效率高。在薄膜二氧化硅上，由CO分解形成的氧会阻塞铁表面，直到〜150°C，此时CO _2的形成会去除表面的氧。相反，在硅载体上，氧很容易溢出到硅上。结果，除氧不再是限速的，铁的碳化可以在较低的温度下进行。

更新日期：2018-06-28

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