Identifying Different Adsorption States of Methanol on ZnO(101̅0): A Scanning Tunneling Microscopy and Density Functional Theory Study

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(1010) 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.