Dudin P, Barinov A, Gregoratti L, Kiskinova M, Esch F, Dri C, Africh C, Comelli G
Sincrotrone Trieste, Area Science Park, I-34012 Basovizza-Trieste, Italy.
J Phys Chem B. 2005 Jul 21;109(28):13649-55. doi: 10.1021/jp0508002.
The formation conditions, morphology, and reactivity of thin oxide films, grown on a Rh(110) surface in the ambient of atomic or molecular oxygen, have been studied by means of laterally resolved core level spectroscopy, scanning tunneling microscopy and low energy electron diffraction. Exposures of Rh(110) to atomic oxygen lead to subsurface incorporation of oxygen even at room temperature and facile formation of an ordered, laterally uniform surface oxide at approximately 520 K, with a quasi-hexagonal structure and stoichiometry close to that of RhO(2). In the intermediate oxidation stages, the surface oxide coexists with areas of high coverage adsorption phases. After a long induction period, the reduction of the Rh oxide film with H(2) is very rapid and independent of the coexisting adsorption phases. The growth of the oxide film by exposure of a Rh(110) surface to molecular oxygen requires higher pressures and temperatures. The important role of the O(2) dissociation step in the oxidation process is reflected by the complex morphology of the oxide films grown in O(2) ambient, consisting of microscopic patches of different Rh and oxygen atomic density.
通过横向分辨芯能级光谱、扫描隧道显微镜和低能电子衍射等手段，研究了在原子氧或分子氧环境中生长在Rh(110)表面的薄氧化膜的形成条件、形貌和反应活性。即使在室温下，Rh(110)暴露于原子氧也会导致氧在次表面的掺入，并在约520 K时易于形成有序的、横向均匀的表面氧化物，其具有准六边形结构且化学计量比接近RhO₂。在中间氧化阶段，表面氧化物与高覆盖度吸附相区域共存。经过长时间的诱导期后，Rh氧化膜用H₂还原非常迅速，且与共存的吸附相无关。通过将Rh(110)表面暴露于分子氧来生长氧化膜需要更高的压力和温度。在O₂环境中生长的氧化膜的复杂形貌反映了O₂解离步骤在氧化过程中的重要作用，该氧化膜由具有不同Rh和氧原子密度的微观斑块组成。
