Adsorption and Diffusion of CO on Clean and CO2-Precovered ZnO(10(1)over-bar0)

The interaction of CO on the clean and a CO2-precovered ZnO(10 (1) over bar0) surface has been investigated with low-temperature scanning tunneling microscopy in combination with density-functional theory calculations. On the clean surface, CO binds weakly to the surface Zn ions and diffuses readily along the [1 (2) over bar 10] direction even at liquid nitrogen temperature. In contrast, the presence of CO, significantly enhances the binding strength of the CO molecules in the vicinity and in turn suppresses their diffusion. These findings are believed to provide new insights of the atomistic interactions of distinct reagents on the ZnO surface, and hence shed light onto the roles of ZnO in the syngas-involved catalytic reactions.