Onderwaater Willem G, Taranovskyy Andriy, van Baarle Gertjan C, Frenken Joost W M, Groot Irene M N
Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands.
European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex 9, France.
J Phys Chem C Nanomater Interfaces. 2017 Jun 1;121(21):11407-11415. doi: 10.1021/acs.jpcc.7b02054. Epub 2017 May 4.
Using a home-built reflectometer, we have investigated the changes in the optical reflectivity of a Pd(100) model catalyst during CO oxidation under high-pressure, high-temperature conditions. We observe changes in optical contrast when exposing the surface to CO oxidation conditions at 200 mbar from room temperature up to 400 °C. These changes in reflectivity are a result both of the formation of a surface oxide layer and of a change in surface roughness because of gas exposure. However, the reflectivity is more sensitive to the presence of a thin, flat oxide layer than to surface roughness. CO oxidation plays an important role in the decrease of the reflectivity. Since adding a reducing agent to the gas mixture renders it unlikely that the oxide thickness increases, we conclude that the observed decrease in reflectivity is dominated by increased surface roughness because of the catalytic reaction. We contribute this observed surface roughening to a Mars-van Krevelen-type reaction mechanism.
我们使用自行搭建的反射仪，研究了Pd(100)模型催化剂在高压、高温条件下CO氧化过程中的光学反射率变化。我们观察到，在200毫巴的压力下，从室温到400°C将表面暴露于CO氧化条件时，光学对比度会发生变化。反射率的这些变化是表面氧化物层形成以及气体暴露导致表面粗糙度变化的结果。然而，反射率对薄而平坦的氧化物层的存在比对表面粗糙度更敏感。CO氧化在反射率降低中起重要作用。由于向气体混合物中添加还原剂使得氧化物厚度不太可能增加，我们得出结论，观察到的反射率降低主要是由于催化反应导致表面粗糙度增加。我们将观察到的这种表面粗糙化归因于Mars-van Krevelen型反应机理。
