Adsorption of carbon monoxide Au/Pd(100) alloys in ultrahigh vacuum: Identification of adsorption sites

作者：Li Zhenjun; Gao Feng; Furlong Octavio; Tysoe Wilfred T^*

来源：Surface Science, 2010, 604(2): 136-143.

DOI：10.1016/j.susc.2009.10.031

• Reflection-adsorption infrared spectroscopy
• Temperature-programmed desorption
• X-ray photoelectron spectroscopy
• Low-energy ion scattering
• Chemisorption
• Palladium-gold alloy
• Carbon monoxide

The adsorption of carbon monoxide is studied on Au/Pd(1 0 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(1 0 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 similar to 350 K corresponding to a desorption activation energy of similar to 117 kJ/mol. However, at lower palladium coverages, these sites are not occupied and CO, desorption states are detected 170 and 112 K corresponding to desorption activation energies of similar to 53 kJ/mol and similar to 35 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.

• 出版日期2010-1-15