Morphology and chemical states of Ni supported on Ti-modified CeOx(111) interfaces

SURFACE SCIENCE

卷:699

Article

Du, Linze¹  Ginting, Elfrida^1,2  Zhou, Jing¹ 

[1] Univ Wyoming, Dept Chem, Laramie, WY 82071 USA

[2] State Univ Medan, Jl Willem Iskandar,Pasar 5, Medan 20221, Sumatera Utara, Indonesia

关键词: Doped ceria;    Mixed oxide;    Metal nanoparticles;    Nickel;    X-ray photoelectron spectroscopy;    Scanning tunneling microscopy;   

DOI  :  10.1016/j.susc.2020.121624

来源: Elsevier

【 摘 要 】

Low coverage of Ni was deposited onto well-ordered Ti-doped CeOx (111) (1.5 < x < 2) thin films at 300 K under ultrahigh vacuum conditions. The morphology and interaction of Ni with Ti-ceria interfaces were investigated with X-ray photoelectron spectroscopy and scanning tunneling microscopy. Ti doped-CeOx (111) mixed oxide interfaces can be prepared by physical vapor deposition of submonolayer coverages of Ti onto both fully oxidized CeO2 (111) and partially reduced thin films (e.g. CeO1.92) at room temperature followed by heating to 700 K. Ti is oxidized to Ti4+ at the cost of ceria reduction. Titania features are uniformly distributed on CeOx with an average height of 0.31 nm. Upon Ni deposition over both Ti-CeO2 (111) and Ti-CeO1.92 surfaces at 300 K, oxidation of Ni to NiO occurs and thus both metallic Ni and Ni2+ species are present in the particles formed over Ti-CeOx surfaces. The extent of Ni oxidation depends on the nature of Ti-CeOx. 28% of deposited Ni is in the +2 state over Ti-CeO2. With heating to 700 K, the percent of the Ni2+ species increases to 37% over Ti-CeO2. However, metallic Ni is the predominant species over Ti-CeO1.92. The difference in the Ni species present in the particles results in a different particle sintering behavior with heating. Compared to pure ceria, modifications of ceria with addition of Ti metal dopants can significantly stabilize Ni as smaller nanoparticles upon heating.

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