Behavior of Supported Palladium Oxide Nanoparticles under Reaction Conditions, Studied with near Ambient Pressure XPS,Analytical Chemistry

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Behavior of Supported Palladium Oxide Nanoparticles under Reaction Conditions, Studied with near Ambient Pressure XPS
Analytical Chemistry ( IF 6.7 ) Pub Date : 2015-07-15 00:00:00 , DOI: 10.1021/acs.analchem.5b01531
Astrid Jürgensen ₁ , Niels Heutz ₂ , Hannes Raschke ₁ , Klaus Merz ₂ , Roland Hergenröder ₁

Affiliation

Near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) is a promising method to close the “pressure gap”, and thus, study the surface composition during heterogeneous reactions in situ. The specialized spectrometers necessary for this analytical technique have recently been adapted to operate with a conventional X-ray source, making it available for routine quantitative analysis in the laboratory. This is shown in the present in situ study of the partial oxidation of 2-propanol catalyzed with PdO nanoparticles supported on TiO₂, which was investigated under reaction conditions as a function of gas composition (alcohol-to-oxygen ratio) and temperature. Exposure of the nanoparticles to 2-propanol at 30 °C leads to immediate partial reduction of the PdO, followed by a continuous reduction of the remaining PdO during heating. However, gaseous oxygen inhibits the reduction of PdO below 90 °C, and the oxidation of 2-propanol to carboxylates only occurs in the presence of oxygen above 90 °C. These results support the theory that metallic palladium is the active catalyst material, and they show that environmental conditions affect the nanoparticles and the reaction process significantly. The study also revealed challenges and limitations of this analytical method. Specifically, the intensity and fixed photon energy of a conventional X-ray source limit the spectral resolution and surface sensitivity of lab-based NAP-XPS, which affect precision and accuracy of the quantitative analysis.

中文翻译：

接近环境压力XPS研究负载型氧化钯纳米粒子在反应条件下的行为

接近环境压力的X射线光电子能谱（NAP-XPS）是弥合“压力差”的一种有前途的方法，因此，可以在原位进行异质反应过程中研究表面成分。最近，这种分析技术所需的专用光谱仪已经过改装，可与常规X射线源配合使用，使其可用于实验室中的常规定量分析。这在用TiO ₂负载在TiO ₂上的PdO纳米颗粒催化的2-丙醇的部分氧化的原位研究中表明了这一点。，这是在反应条件下根据气体组成（醇与氧的比率）和温度的函数进行研究的。将纳米颗粒在30°C下暴露于2-丙醇会导致PdO立即部分还原，然后在加热过程中连续还原残留的PdO。但是，气态氧气会在90°C以下抑制PdO的还原，只有在温度高于90°C的氧气存在下，2-丙醇才能氧化为羧酸盐。这些结果支持金属钯是活性催化剂材料的理论，并且它们表明环境条件显着影响纳米颗粒和反应过程。该研究还揭示了这种分析方法的挑战和局限性。具体来说，

更新日期：2015-07-15

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