利用扫描隧道显微镜(STM)和X射线光电子能谱(XPS)对Pt(111)表面制备的Fe单层薄膜及其在不同环境气氛条件下的多种结构进行了研究.在温度为487K的Pt(111)表面制备出了完整的Fe单层薄膜Fe/Pt(111).对Fe/Pt(111)依次升高温度进行超高真空退火,STM和XPS结果表明退火温度高于800 K时,表面Fe原子扩散到次表层区域,形成次表层Fe结构Pt/Fe/Pt(111).Pt/Fe/Pt(111)在O_2氧化气氛中经850 K退火可转变成表面FeO薄膜FeO/Pt(111).FeO/Pt(111)结构在温和的H_2还原气氛中(600K)转变成表面Fe结构,进一步的还原处理(800K)则可以重新生成Pt/Fe/Pt(111).控制样品的环境气氛在O_2和H_2之间切换,使得表面Fe(FeO)和次表面Fe可以重复地转变.本研究实现了多种Fe-Pt表面结构的可控制备,可为合理地设计高效、价廉的催化剂提供借鉴.
Monolayer Fe films on Pt(111) and their derived structures under different environments were investigated by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). The growth of monolayer Fe films was seen at 487 K. The surface compo-sition and structure of the Fe/Pt(111) surface were monitored by XPS and STM during stepwise annealing under vacuum. Surface Fe was driven into the subsurface region during annealing above 800 K. This resulted in a Pt-skin surface of Pt/Fe/Pt(111). Oxidation of the Pt-skin structure in O_2 produced a FeO surface structure, FeO/Pt(111). This was transformed into a surface Fe structure by mild reduction in H_2 (600 K) and into subsurface Fe by further severe reduction (800 K). The transformation of surface Fe (FeO) and subsurface Fe in Pt(111) was reversible in cycled oxidation and reduction treatments. The results demonstrated the controlled preparation of various Fe-Pt surfaces. This can be important for the design of high-performance and low-cost catalysts.
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