Formation of Nanometer-Sized Surface Platinum Oxide Clusters on a Stepped Pt(557) Single Crystal Surface Induced by Oxygen: A High-Pressure STM and Ambient-Pressure XPS Study
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- 作者：Zhongwei Zhu ; Franklin (Feng) Tao ; Fan Zheng ; Rui Chang ; Yimin Li ; Lars Heinke ; Zhi Liu ; Miquel Salmeron ; Gabor A. Somorjai
- 刊名：Nano Letters
- 出版年：2012
- 出版时间：March 14, 2012
- 年：2012
- 卷：12
- 期：3
- 页码：1491-1497
- 全文大小：421K
- 年卷期：v.12,no.3(March 14, 2012)
- ISSN：1530-6992
文摘
We studied the oxygen-induced restructuring process on a stepped Pt(557) single crystal surface using high-pressure scanning tunneling microscopy (HP-STM) and ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) at O2 pressures up to 1 Torr. HP-STM has revealed that nanometer-sized clusters are created on Pt(557) at 1 Torr of O2 and at room temperature. These clusters are identified as surface Pt oxide by AP-XPS. The appearance of clusters is preceded by the formation of 1D chain structures at the step edges. By using a Pt(111) surface as a reference, it was found that the step sites are the nucleation centers for the formation of surface oxide clusters. These surface oxide clusters disappear and the stepped structure is restored on Pt(557) after evacuating O2 to 10鈥? Torr. Changes in the surface oxide concentration in response to variations in the O2 gas pressure are repeatable for several cycles. Our results that small clusters are initiated at step sites at high pressures demonstrate the importance of performing in situ characterization of stepped Pt catalysts under reaction conditions.