Unraveling the atomic structure and dissociation of interfacial water on anatase TiO (101) under ambient conditions with solid-state NMR spectroscopy.

Anatase TiO is a widely used component in photo- and electro-catalysts for water splitting, and the (101) facet of anatase TiO is the most commonly exposed surface. A detailed understanding of the behavior of HO on this surface could provide fundamental insights into the catalytic mechanism. This, however, is challenging due to the complexity of the interfacial environments, the high mobility of interfacial HO, and the interference from outer-layer HO. Herein, we investigate the HO/TiO interface using advanced solid-state NMR techniques. The atomic-level structures of surface O sites, OH groups, and adsorbed HO have been revealed and the detailed interactions among them are identified on the (101) facet of anatase TiO. By following the quantitative evolution of surface O and OH sites along with HO loading, it is found that more than 40% of the adsorbed water spontaneously dissociated under ambient conditions on the TiO surface at a loading of 0.3 mmol HO/g, due to the delicate interplay between water-surface and water-water interactions. Our study highlights the importance of understanding the atomic-level structures of HO on the surface of TiO in catalytic reactions. Such knowledge can promote the design of more efficient catalytic systems for renewable energy production involving activation of water molecules.