کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5426740 | 1395900 | 2006 | 10 صفحه PDF | دانلود رایگان |

The interaction of O2 with Pd(1Â 1Â 1), Pd(1Â 1Â 0) and Pd(1Â 0Â 0) was studied in the pressure range 1-150Â Torr by the techniques of temperature programmed decomposition (TPD), Auger electron spectroscopy (AES) and low energy electron diffraction (LEED). The oxidation of Pd was rate-determined by oxygen diffusion into Pd metal followed by the diffusion into PdO once the bulk oxide layer was formed. The dissolution of oxygen atoms into Pd metal followed the Mott-Cabrera model with diffusion coefficient 10â16Â cm2Â sâ1 at 600Â K and activation energy of 60-85Â kJÂ molâ1. The bulk oxide phase was formed when a critical oxygen concentration was reached in the near-surface region. The formation of PdO was characterized by a decrease in the oxygen uptake rate, the complete fading of the metallic Pd LEED pattern and an atomic ratio O/Pd of 0.15-0.7 as measured by AES. The diffusion of oxygen through the bulk oxide layer again conformed to the Mott-Cabrera parabolic diffusion law with diffusion coefficient 10â18Â cm2Â sâ1 at 600Â K and activation energy of 111-116Â kJÂ molâ1. The values for the diffusion coefficient and apparent activation energy increased as the surface atom density of the single crystals increased.
Journal: Surface Science - Volume 600, Issue 13, 1 July 2006, Pages 2752-2761