期刊
NANO LETTERS
卷 12, 期 3, 页码 1491-1497出版社
AMER CHEMICAL SOC
DOI: 10.1021/nl204242s
关键词
Stepped Pt single crystal; HP-STM; AP-XPS; surface oxide
类别
资金
- Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, of the U.S. Department of Energy [DE-AC02-05CH11231]
- Direct For Mathematical & Physical Scien
- Division Of Chemistry [1126374] Funding Source: National Science Foundation
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 O-2 pressures up to 1 Torr. HP-STM has revealed that nanometer-sized clusters are created on Pt(557) at 1 Torr of O-2 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 O-2 to 10(-8) Torr. Changes in the surface oxide concentration in response to variations in the O-2 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.
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