Formation of Metastable Water Chains on Anatase TiO2(101)

Anatase TiO2 is indispensable material for energy-harvesting applications and catalysis. In this study, we employ scanning tunneling microscopy and study water adsorption on most stable TiO2(101) surface of anatase. We demonstrate that at very low temperatures (80 K) water has the transient mobility that allows it to move on the surface and form extended chains. In contrast with many other oxides, these water chains are only metastable in nature. Adsorption at higher temperatures, where sustained diffusion is observed (190 K), leads to isolated water monomers in accord with prior literature. We speculate that the observed low-temperature mobility is a result of adsorption in a long-lived precursor state with a low diffusion barrier.