CO oxidation by atomically adsorbed oxygen on Ag(110) in the temperature range 100-300 K

The catalytic CO oxidation reaction with atomically adsorbed oxygen on Ag(110) has been analyzed by means of molecular beam titration, molecular beam relaxation (MBRS), qualitative LEED, and reactive thermal desorption measurements (RTDS). The reaction has been observed and characterized in the temperature range 100-300 K. The CO2 formation rate depends strongly on the reaction temperature. Additionally, the angular distribution of the desorbing CO2 is strongly peaked along the surface normal independent of the angle of incidence. Consequently, a Langmuir-Hinshelwood (LH) type model has to be applied for the whole reaction temperature range. The titration curves show two separate structures which are assigned to two reaction channels due to the existence of kinetically distinct oxygen species. These oxygen species are metastable in the sense that they are passivated in a thermally activated process which is proposed to be connected with the formation of the oxygen-induced reconstruction. The stabilized oxygen reacts again with CO at higher temperatures (above 250 K). A reaction scheme is presented which consistently reproduces the experimental results and allows the determination of the kinetic parameters of the reaction.