物理化学学报 >> 2015, Vol. 31 >> Issue (11): 2151-2157.doi: 10.3866/PKU.WHXB201510083

催化和表面科学 上一篇    下一篇

Ni在ZrO2(111)薄膜表面的生长、电子结构及热稳定性

韩永,徐倩,鞠焕鑫,朱俊发*()   

  • 收稿日期:2015-08-06 发布日期:2015-11-13
  • 通讯作者: 朱俊发 E-mail:jfzhu@ustc.edu.cn
  • 基金资助:
    国家自然科学基金(U1232102, 21403205);国家重点基础研究发展规划项目(973)(2013CB834605)

Growth, Electronic Structure and Thermal Stability of Ni on ZrO2(111) Thin Film Surfaces

Yong. HAN,Qian. XU,Huan-Xin. JU,Jun-Fa. ZHU*()   

  • Received:2015-08-06 Published:2015-11-13
  • Contact: Jun-Fa. ZHU E-mail:jfzhu@ustc.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(U1232102, 21403205);National Key Basic Research Programof China (973)(2013CB834605)

摘要:

利用X射线光电子能谱、紫外光电子能谱和低能电子衍射研究了Ni纳米颗粒在ZrO2(111)薄膜表面的生长模式、电子结构及热稳定性. ZrO2(111)薄膜外延生长于Pt(111)单晶表面,厚度约为3 nm.结果表明,当Ni气相沉积到ZrO2(111)薄膜表面上时,遵循Stranski-Krastanov生长模式,即先二维生长至0.5 ML(monolayer),然后呈三维岛状生长.随着覆盖度的减小, Ni 2p3/2峰逐渐向高结合能位移.利用俄歇参数法分析发现,引起该峰向高结合能位移的主要原因来源于终态效应的贡献,但在低的Ni覆盖度时,也有部分初态效应的贡献,说明Ni在ZrO2表面初始生长时,两者存在较强的界面相互作用, Ni向ZrO2衬底传递电荷,形成带部分正电荷的Niδ+.两种不同覆盖度(0.05和0.5 ML)的Ni/ZrO2(111)模型催化剂热稳定性研究表明,当温度升高时, Ni逐渐被氧化成Ni2+,并伴随着向ZrO2衬底的扩散.本文从原子水平上认识了Ni与ZrO2表面的相互作用和界面结构,为理解实际ZrO2担载的Ni催化剂结构提供了重要的依据.

关键词: 镍, 二氧化锆, 模型催化剂, X射线光电子能谱, 紫外光电子能谱

Abstract:

The growth mode, electronic structure, and thermal stability of Ni nanoparticles on thin ZrO2(111) film surfaces were investigated using X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and low-energy electron diffraction. Stoichiometric ZrO2(111) thin films with thickness of 3 nm were epitaxially grown on a Pt(111) single-crystal surface. The results indicate that the growth of Ni vapor deposited on thin ZrO2(111) films follows two-dimensional growth up to 0.5 ML (monolayer), followed by threedimensional growth (i.e., the Stranski-Krastanov growth mode). The Ni 2p3/2 binding energy (BE) increases with decreasing Ni coverage. We used the Auger parameter method to differentiate the contributions to this BE shift from the initial-state and final-state effects. The main contribution to the Ni 2p core level BE shift is made by the final-state effect. However, at low Ni coverages, the initial-state effect also contributes. This suggests that at the initial stage of Ni growth on the ZrO2(111) surface, Ni and ZrO2 interact strongly, leading to charge transfer from Ni to the ZrO2 substrate, with the appearance of partially positively charged Niδ+. Thermal stability studies of Ni/ZrO2(111) model catalysts with two different coverages (0.05 and 0.5 ML) indicate further oxidation of Ni to Ni2+ and concurrent diffusion of Ni into the ZrO2 substrate at elevated temperatures. These findings provide an atomic-level fundamental understanding of the interactions between Ni with ZrO2, which is essential for identifying the structures of real ZrO2-supported Ni catalysts.

Key words: Nickel, Zirconia, Model catalyst, X-ray photoelectron spectroscopy, Ultraviolet photoelectron spectroscopy

MSC2000: 

  • O643