Origin of hydroxyl pair formation on reduced anatase TiO2(101)

The interaction of water with metal oxide surfaces is of key importance to several research fields and applications. Because of its ability to photo-catalyze water splitting, reducible anatase TiO2 (a-TiO2) is of particular interest. Here, we combine experiments and theory to study the dissociation of water on bulk-reduced a-TiO2(101). Following large water exposures at room temperature, point-like protrusions appear on the a-TiO2(101) surface, as shown by scanning tunneling microscopy (STM). These protrusions originate from hydroxyl pairs, consisting of terminal and bridging OH groups, OHt/OHb, as revealed by infrared reflection absorption spectroscopy (IRRAS) and valence band experiments. Utilizing density functional theory (DFT) calculations, we offer a comprehensive model of the water/a-TiO2(101) interaction. This model also explains why the hydroxyl pairs are thermally stable up to similar to 480 K.

Automated summary

The interaction between water and metal oxide surfaces is crucial in various research fields and applications, especially reducible anatase TiO2. This study combines experiments and theory to investigate the dissociation of water on bulk-reduced a-TiO2(101). The results show that after water exposure, point-like protrusions appear on the a-TiO2(101) surface, which originate from hydroxyl pairs (OHt/OHb). The study also provides a comprehensive model of the water/a-TiO2(101) interaction and explains the thermal stability of the hydroxyl pairs up to 480 K.