Carbon Monoxide Adsorption On Pd-deposited Cu(1 1 0) Surface: Infrared Reflection Absorption And Temperature Programmed Desorption Studies

摘要

We investigated carbon monoxide (CO) adsorption and desorption behaviors on 0.1-nm-, 0.15-nm-, and 0.3-nm-thick-Pd-deposited Cu(1 1 0) surfaces using infrared reflection absorption (IRRAS) and temperature-programmed desorption (TPD) spectroscopic methods. CO was exposed to the 0.1-nm-thick-Pd/Cu( 1 1 0) surface at the substrate temperature of 90 K. The IR band attributable to CO bonded to Cu atoms emerged at 2092 cm~(-1): the band was located at 2100 cm~(-1) at saturation coverage, with a shoulder at 2110 cm~(-1). In addition to these bands, weak absorptions attributable to the Pd-CO bonds appeared at 2050 and 1960 cm~(-1). With increasing Pd thickness, the Pd related-bands became increasingly prominent Particularly at the early stage of exposure, the band at 2115 cm~(-1) became visible. The band at 2117 cm~(-1) dominated the spectra all through the exposures for the 0.3-nm-thick-Pd surface. The TPD spectra of the surfaces showed two remarkable features at around 220-250 and 320-390 K, ascribable, respectively, to Cu-CO and Pd-CO. The desorption peaks shifted to higher temperatures with increasing Pd thickness. Based on the TPD and IRRAS results, we discuss the adsorption-desorption behaviors of CO on the Pd/Cu(1 1 0) surfaces.