Low-Temperature Heterolytic Adsorption of H₂ on ZnO(1010) Surface

Abstract

The interaction of molecular hydrogen with a ZnO(101̅0) surface at cryogenic conditions was investigated by in situ scanning tunneling microscopy (STM) experiments combined with density functional theory (DFT) calculations. The H2 molecules were found splitting at an extremely low temperature ∼20 K and growing into a novel one-dimensional chain structure along the [0001] direction, which extends as long as several hundred nanometers and possesses substantial thermal stability up to ∼220 K. Both high-resolution STM images and DFT calculations reveal that the initial H2 splitting occurs through a physisorbed precursor state followed by forming heterolytic bonds to the Zn and O ions belonging to two neighbored Zn–O pairs of the ZnO(101̅0) surface. These findings have shed new light on the active roles of ZnO in various hydrogen-related techniques as well as in hydrogenation reactions.