Carbon monoxide adsorption on Pd-deposited Cu(1 1 0) surface: Infrared reflection absorption and temperature programmed desorption studies

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 Pdsingle bondCO 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 Cusingle bondCO and Pdsingle bondCO. 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.