کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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5424339 | 1395820 | 2010 | 8 صفحه PDF | دانلود رایگان |
The adsorption of carbon monoxide is studied on Au/Pd(1Â 0Â 0) alloys by means of reflection-absorption infrared spectroscopy (RAIRS) and temperature-programmed desorption (TPD). The alloy was formed by adsorbing a four-monolayer thick gold film on a Pd(1Â 0Â 0) substrate and by heating to various temperatures to form alloys with a range of palladium coverages. The alloy was characterized using X-ray photoelectron spectroscopy and the composition of the outermost layer measured using low-energy ion scattering spectroscopy. CO adsorbs on palladium bridge sites only for palladium coverages greater than 0.5 monolayers (ML) suggesting that next-nearest neighbor sites are preferentially populated by palladium atoms. CO adsorbs on atop palladium sites and desorbs at â¼350Â K corresponding to a desorption activation energy of â¼117Â kJ/mol. However, at lower palladium coverages, these sites are not occupied and CO desorption states are detected 170 and 112Â K corresponding to desorption activation energies of â¼53Â kJ/mol and â¼35Â kJ/mol, respectively, for these states. It is suggested that these states are due to a restructuring of the surface to form low-coordination gold sites that obscure the atop palladium site.
Journal: Surface Science - Volume 604, Issue 2, 15 January 2010, Pages 136-143