Nakai Ikuyo, Kondoh Hiroshi, Shimada Toru, Resta Andrea, Andersen Jesper N, Ohta Toshiaki
Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
J Chem Phys. 2006 Jun 14;124(22):224712. doi: 10.1063/1.2205856.
We studied the mechanism of CO oxidation on O-precovered Pd(111) surfaces by means of fast x-ray photoelectron spectroscopy (XPS). The oxygen overlayer is compressed upon CO coadsorption from a p(2 x 2) structure into a (square root(3) x square root(3))R30 degrees structure and then into a p(2 x 1) structure with increasing CO coverage. These three O phases exhibit distinctly different reactivities. (1) The p(2 x 2) phase does not react with CO unless the surface temperature is sufficiently high (<290 K). (2) In the square root(3) x square root(3))R30 degrees phase, the reaction occurs exclusively at island peripheries. CO molecules in a high-density phase formed under CO exposure react with oxygen atoms, leading to quite a small apparent activation energy. (3) The reaction proceeds uniformly over the islands in the p(2 x 1) phase.
我们借助快速X射线光电子能谱（XPS）研究了在预覆盖氧的Pd(111)表面上CO氧化的机理。随着CO共吸附，氧覆盖层从p(2×2)结构压缩为（√3×√3）R30°结构，然后随着CO覆盖度的增加进一步压缩为p(2×1)结构。这三种氧相表现出明显不同的反应活性。（1）p(2×2)相不与CO反应，除非表面温度足够高（<290 K）。（2）在（√3×√3）R30°相中，反应仅在岛的边缘发生。在CO暴露下形成的高密度相中的CO分子与氧原子反应，导致相当小的表观活化能。（3）反应在p(2×1)相的岛上均匀进行。
