Atomic insights into the interaction of CO 2 with the mixed-terminated ZnO(101̅ 0) surface were achieved in detail by low-temperature scanning tunneling microscopy (LT-STM) together with density functional theory (DFT) calculations. The binding site and adsorption geometry were directly imaged by LT-STM, revealing that the CO 2 molecules are chemisorbed and turned into surface carbonate species. The strong interaction of CO 2 with the ZnO(101̅ 0) surface in turn activates the surface, i.e., reconstructs the local surface such that facilitates further CO 2 bindings, leading to the formation of a one-dimensional assembly structure which grows along the [0001̅ ] direction. DFT simulations indicated that the superior agglomeration energies along ⟨0001̅ ⟩ directions as well as the CO 2 -induced surface reconstruction are responsible for the directional growth of the surface carbonate chains.

The interaction of CO on the clean and a CO 2 -precovered ZnO(101̅ 0) 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 [12̅ 10] direction even at liquid nitrogen temperature. In contrast, the presence of CO 2 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 syngasinvolved catalytic reactions.

The adsorption and organization state of methanol on the ZnO surface is of importance for understanding the mechanism of the related (photo)­catalytic reactions. In this work, by using high-resolution scanning tunneling microscopy in combination with density functional theory, we have unambiguously identified both the physi- and chemisorbed methanol species on the nonpolar ZnO(101̅0) surface, whose distribution obviously depends on the temperature. The physisorption of methanol dominates at liquid nitrogen temperature but can transform into chemisorption upon either thermal annealing or electron injection. Moreover, the chemisorbed methanol mostly retains an undissociated state and tends to form a special one-dimensional chain structure along the [0001] direction mediated by the intermolecular hydrogen bonding interactions. These findings are believed to provide fundamental information for a deepened understanding of methanol chemistry over the ZnO surface.