Kinetics of low-temperature CO oxidation on Au(111)

Abstract

The oxidation of carbon monoxide on oxygen-modified Au(111) surfaces is studied using a combination of reflection-absorption infrared spectroscopy (RAIRS) and temperature-programmed desorption (TPD). TPD reveals that CO desorbs in two states with the low-temperature state have a peak temperature between ~130 and 150 K, and the higher-temperature state having a peak temperature that varies from ~175 to ~220 K depending on the initial oxygen and CO coverages. Infrared spectroscopy indicates that the low-temperature CO desorption state is predominantly associated with CO adsorbed on Au δ+ sites, while the higher-temperature states are due to CO on Au0 sites. No additional vibrational features are detected indicating that CO reacts directly with adsorbed atomic oxygen on gold to form CO2. Estimates of the activation energy for CO2 formation suggest that they are in the same range and found for supported gold catalysts at reaction temperature below ~300 K.