Reaction properties of NO and CO over an Ir(211) surface

Abstract

The adsorption and thermal reactivity of NO and CO over an Ir(211) surface were studied using x-ray photoelectron spectroscopy, infrared reflection absorption spectroscopy, and temperature-programed desorption. NO adsorbed on the atop site of the (111) terrace and the bridge site of the (100) step at 273K. In contrast, CO adsorbed only on the atop site at 273K, initially on the (111) terrace and then on the (100) step. Both atop NO and bridge NO decomposed to N2 through the recombination of atomic nitrogen, indicating that the Ir(211) surface provides high NO dissociation activity. When NO and CO were coadsorbed, the preadsorption of atop CO on the terrace sites selectively inhibited the adsorption of atop NO on the terrace sites, while preadsorption of atop CO on the step sites significantly inhibited the adsorption of bridge NO on the step sites. These results indicate that NO may be selectively reduced by CO in the presence of O2 when Ir(211) is used as the catalyst.