Department of Chemistry, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland.
J Chem Phys. 2010 Aug 28;133(8):084704. doi: 10.1063/1.3464481.
Density functional calculations were performed in order to investigate CO oxidation on two of the most stable bulk PdO surfaces. The most stable PdO(100) surface, with oxygen excess, is inert against CO adsorption, whereas strong adsorption on the stoichiometric PdO(101) surface leads to favorable oxidation via the Langmuir-Hinshelwood mechanism. The reaction with a surface oxygen atom has an activation energy of 0.66 eV, which is comparable to the lowest activation energies observed on metallic surfaces. However, the reaction rate may be limited by the coverage of molecular oxygen. Actually, the reaction with the site blocking molecular oxygen is slightly more favorable, enabling also possible formation of carbonate surface species at low temperatures. The extreme activity of strongly bonded surface oxygen atoms is more greatly emphasized on the PdO(100)-O surface. The direct reaction without adsorption, following the Eley-Rideal mechanism and taking advantage of the reaction tunnel provided by the adjacent palladium atom, has an activation energy of only 0.24 eV. The reaction mechanism and activation energy for the palladium activated CO oxidation on the most stable PdO(100)-O surface are in good agreement with experimental observations.
为了研究 CO 在两种最稳定的体相 PdO 表面上的氧化反应，我们进行了密度泛函计算。富氧的最稳定 PdO(100)表面对 CO 吸附惰性，而在化学计量比的 PdO(101)表面上的强烈吸附则通过 Langmuir-Hinshelwood 机制有利于氧化。与表面氧原子的反应具有 0.66 eV 的活化能，与金属表面上观察到的最低活化能相当。然而，反应速率可能受到分子氧覆盖率的限制。实际上，与位阻分子氧的反应稍微更有利，也能在低温下形成碳酸盐表面物种。在 PdO(100)-O 表面上，强键合表面氧原子的极端活性更为突出。直接反应，遵循 Eley-Rideal 机制，利用相邻钯原子提供的反应隧道，其活化能仅为 0.24 eV。在最稳定的 PdO(100)-O 表面上，钯原子促进的 CO 氧化反应的反应机制和活化能与实验观察结果相符。
