Institut für Physik, Carl von Ossietzky Universität, D-26111 Oldenburg, Germany.
J Chem Phys. 2019 Mar 28;150(12):124701. doi: 10.1063/1.5091102.
The alumina film formed by oxidation of NiAl(110) has gained enormous attention as a surface-science compatible model system for a crystalline and atomically flat oxide surface. A main disadvantage is its small thickness of only 0.5 nm that limits possible uses in catalytic studies at elevated temperature and pressure. This work demonstrates how small amounts of tungsten pre-deposited onto the NiAl surface modify the oxidation characteristic. Oxidizing the surface at 850 K in the presence of W particles increases the film thickness to 2.5 nm, a value that rises to more than 5 nm at 1050 K oxidation temperature. Thickness, stoichiometry, and morphology of the thickened alumina films are analyzed in detail by means of X-ray photoelectron spectroscopy, electron-diffraction, and scanning tunneling microscopy. The promoted oxide formation is ascribed to the unique redox properties of tungsten that stabilizes O molecules from the gas phase and produces active oxygen species for further reaction.
氧化铝薄膜通过 NiAl(110) 的氧化形成，作为一种与表面科学兼容的晶体和原子级平整氧化物表面的模型系统，引起了极大的关注。一个主要的缺点是其厚度只有 0.5nm，这限制了在高温高压下的催化研究中的可能应用。这项工作表明，少量的钨预先沉积在 NiAl 表面上如何改变氧化特性。在 850K 下，在存在 W 颗粒的情况下氧化表面会将膜厚度增加到 2.5nm，而在 1050K 的氧化温度下，厚度会增加到超过 5nm。通过 X 射线光电子能谱、电子衍射和扫描隧道显微镜详细分析了增厚氧化铝薄膜的厚度、化学计量和形态。这种促进的氧化形成归因于钨的独特氧化还原性质，它稳定了气相中的 O 分子，并产生了活性氧物种，以进行进一步的反应。
