Reaction mechanism for CO oxidation on Cu(3 1 1): A density functional theory study

The microscopic reaction mechanism for CO oxidation on Cu(3 1 1) surface has been investigated by means of comprehensive density functional theory (DFT) calculations. The elementary steps studied include O2 adsorption and dissociation, dissociated O atom adsorption and diffusion, as well as CO adsorption and oxidation on the metal. Our results reveal that O2 is considerably reactive on the Cu(3 1 1) surface and will spontaneously dissociate at several adsorption states, which process are highly dependent on the orientation and site of the adsorbed oxygen molecule. The dissociated O atom may likely diffuse via inner terrace sites or from a terrace site to a step site due to the low barriers. Furthermore, we find that the energetically most favorable site for CO molecule on Cu(3 1 1) is the step edge site. According to our calculations, the reaction barrier of CO + O → CO2 is about 0.3 eV lower in energy than that of CO + O2 → CO2 + O, suggesting the former mechanism play a main role in CO oxidation on the Cu(3 1 1) surface.