Interaction of Methanol and Hydrogen on a ZnO (0001) Single Crystal Surface

Abstract

Thermal reactions of CH3OH on a ZnO (0001) surface with and without coadsorbed atomic hydrogen have been investigated using a temperature-programmed desorption (TPD) technique. Both H-2 and CH2O desorb at 510 and 580 K during CH3OH decomposition on ZnO(0001). When H atoms are adsorbed on ZnO(0001), the recombinative desorption of H-2 takes place at around 450 K. In the process of CH3OH decomposition on ZnO(0001), H-2 desorption is not observed until the surface temperature reaches 510 K. These observations indicate that surface-bound H atoms are not produced up to 510 K. When CD3OD and H are coadsorbed, the desorption of both H-2 and HD is observed at 445 K. HD should be formed by the exchange reaction between CD3O-D and H on the surface, which indicates that the CD3O-D bond is partially broken to form an associative CD3 center dot center dot center dot D complex. We suggest two different pathways for the formation of CH2O from CH3OH on ZnO(0001). At 510 K, CH2O and H-2 are formed from the surface reaction of CH3O and H. Desorption of CH2O at 580 K is related to the complete decomposition of CH3O.