کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5425408 | 1395855 | 2007 | 9 صفحه PDF | دانلود رایگان |
The adsorption of ethylene on gold-palladium alloys formed on a Pd(1Â 1Â 1) surface is investigated using a combination of temperature-programmed desorption (TPD) and reflection absorption infrared spectroscopy (RAIRS). Various alloy compositions are obtained by depositing four monolayers of gold on a clean Pd(1Â 1Â 1) surface and annealing to various temperatures. For gold coverages greater than â¼0.7, ethylene adsorbs primarily on gold sites, desorbing with an activation energy of less than 55Â kJ/mol. At gold coverages between â¼0.5 and â¼0.7, ethylene is detected on palladium sites in a Ï-bonded configuration (with a Ï-Ï parameter of â¼0.1) desorbing with an activation energy of between â¼57 and 62Â kJ/mol. Further reducing the gold coverage leads to an almost linear increase in the desorption activation energy of ethylene with increasing palladium content until it eventually reaches a value of â¼76Â kJ/mol found for ethylene on clean Pd(1Â 1Â 1). A corresponding increase in the Ï-Ï parameter is also found as the gold coverage decreases reaching a value of â¼0.8, assigned to di-Ï-bonded ethylene as found on clean Pd(1Â 1Â 1).
Journal: Surface Science - Volume 601, Issue 3, 1 February 2007, Pages 714-722