Unveiling the Surface Structure of ZnO Nanorods and H 2 Activation Mechanisms with 17 O NMR Spectroscopy.

ZnO plays a very important role in many catalytic processes involving H 2 , yet the details on their interactions and H 2 activation mechanism are still missing, owing to the lack of a characterization method that provides resolution at the atomic scale and follows the fate of oxide surface species. Here, we apply 17 O solid-state NMR spectroscopy in combination with DFT calculations to unravel the surface structure of ZnO nanorods and explore the H 2 activation process. We show that six different types of oxygen ions in the surface and subsurface of ZnO can be distinguished. H 2 undergoes heterolytic dissociation on three-coordinated surface zinc and oxygen ions, while the formed hydride species migrate to nearby oxygen species, generating a second hydroxyl site. When oxygen vacancies are present, homolytic dissociation of H 2 occurs and zinc hydride species form from the vacancies. Reaction mechanisms on oxide surfaces can be explored in a similar manner.