Superwetting of TiO 2 by light-induced water-layer growth via delocalized surface electrons

Significance TiO 2 , which is chemically stable, harmless, and inexpensive, has been widely used for industrial applications. Recently, TiO 2 -coated materials, exhibiting superwetting under sunlight, have been developed for environmental solutions. However, the mechanism responsible for superwetting of TiO 2 is still in controversy despite many studies. We clarified its origin by performing tip-based in situ measurements of the growth dynamics of the photo-adsorbed water layers, as associated with delocalized surface electrons. Combined with molecular dynamics simulations, we provided conclusive clues that the “water wets water” process promotes water adsorption on the water layers, producing superwetting.