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通过X射线光电子能谱和俄歇电子能谱对氧化(350℃,空气中)和还原(480℃氢气流中)状态的Pt—Ir/γ—Al_2O_3和Pt—Ir/SiO_2模型催化剂的表面特征进行了研究。试验发现,氧化状态下,样品表面上主要是PtO_2和Ir的高价氧化物以及少量PtO,还原过程使这些氧化物转化为金属,主要是以微细的金属簇的形式分散在表面上。Pt和Ir之间存在相互作用,是形成双金属簇的表现,同时还有少量由于金属烧结过程形成的较大的金属粒子,该状态下的Pt_(4f)和Ir_(4f)结合能较前者略低;SiO_2载体上的铂和铱的原子浓度与在γ—Al_20_3上有明显差异。
The surface characteristics of Pt-Ir / γ-Al_2O_3 and Pt-Ir / SiO_2 catalysts for oxidation (350 ℃ in air) and reduction (480 ℃ hydrogen flow) were investigated by XPS and Auger electron spectroscopy Were studied. It was found that in the oxidized state, the surface of the sample mainly consists of the high-valent oxides of PtO 2 and Ir together with a small amount of PtO. The reduction process converts these oxides into metals, mainly on the surface in the form of fine clusters of metals. The interaction between Pt and Ir is the result of the formation of bimetallic clusters with a small amount of larger metal particles formed by the sintering of metals. In this state, the binding energies of Pt 4 F and Ir 4 F are higher than those of the former Slightly lower; the atomic concentrations of platinum and iridium on the SiO 2 carrier are significantly different from those on γ-Al 2 O 3.