Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands.
Phys Chem Chem Phys. 2011 Aug 7;13(29):13167-71. doi: 10.1039/c1cp20989b. Epub 2011 Jun 16.
The surface structure of Pd(100) during CO oxidation was measured using a combination of a flow reactor and in situ surface X-ray diffraction coupled to a large-area 2-dimensional detector. The surface structure was measured for P(O(2))/P(CO) ratios between 0.6 and 10 at a fixed total gas pressure of 200 mbar and a fixed CO pressure of 10 ± 1 mbar. In conjunction with the surface structure the reactivity of the surface was also determined. For all P(O(2))/P(CO) ratios the surface was found to oxidize above a certain temperature. Three different types of oxides were observed: the surface oxide, an epitaxial layer of bulk-like PdO, and a non-epitaxial layer of bulk-like PdO. As soon as an oxide was present the reactivity of the surface was found to be mass transfer limited by the flux of CO molecules reaching the surface.
使用结合了流动反应器和原位表面 X 射线衍射与大面积 2 维探测器的方法，测量了 Pd(100) 在 CO 氧化过程中的表面结构。在总气压为 200 毫巴和 CO 压力为 10 ± 1 毫巴固定的情况下，在 P(O(2))/P(CO) 比值在 0.6 到 10 之间测量了表面结构。结合表面结构，还确定了表面的反应性。对于所有的 P(O(2))/P(CO) 比值，发现表面在一定温度以上会发生氧化。观察到三种不同类型的氧化物：表面氧化物、体相 PdO 的外延层和体相 PdO 的非外延层。一旦存在氧化物，表面的反应性就会受到到达表面的 CO 分子通量的限制，成为质量传递限制。
