Fakultät für Physik, Universität Wien, Sensengasse 8, A-1090 Wien, Austria.
J Chem Phys. 2010 Jan 14;132(2):024711. doi: 10.1063/1.3290813.
The catalytic activity of palladium toward selective hydrogenation of hydrocarbons depends on the partial pressure of hydrogen. It has been suggested that the reaction proceeds selectively toward partial hydrogenation only when a carbon-rich film is present at the metal surface. On the basis of first-principles simulations, we show that carbon can dissolve into the metal because graphite formation is delayed by the large critical nucleus necessary for graphite nucleation. A bulk carbide Pd(6)C with a hexagonal six-layer fcc-like supercell forms. The structure is characterized by core level shifts of 0.66-0.70 eV in the core states of Pd, in agreement with experimental x-ray photoemission spectra. Moreover, this phase traps bulk-dissolved hydrogen, suppressing the total hydrogenation reaction channel and fostering partial hydrogenation.
钯对碳氢化合物选择性加氢的催化活性取决于氢气的分压。有人认为，只有当金属表面存在富碳膜时，反应才会选择性地进行部分加氢。基于第一性原理模拟，我们表明，由于石墨成核所需的临界核较大，导致石墨形成延迟，因此碳可以溶解到金属中。形成了具有六方六层层状 fcc 类似超胞的块状碳化物 Pd(6)C。该结构的特征在于钯的芯态中芯能级位移为 0.66-0.70 eV，与实验的 X 射线光电子能谱一致。此外，该相捕获了体相溶解的氢，抑制了总加氢反应通道，促进了部分加氢。
