Surface hydroxylation of TiO2 yields notable visible-light photocatalytic activity to decompose rhodamine B in aqueous solution

●Ball milled TiO2 decomposes rhodamine B under visible light irradiation.●Ball-milling of TiO2 in aqueous medium yields a hydroxyl-rich surface layer.●The hydroxyl-rich layer facilitates dye adsorption on TiO2.●It also facilitates charge transfer to/from TiO2 under visible light irradiation.

A hydroxyl-rich layer forms on the surface of TiO2 by simple ball milling in aqueous medium. This layer facilitates the surface adsorption of the rhodamine B (RhB) molecules and yields a notable Vis-light photocatalytic activity for RhB decomposition in aqueous solution, demonstrating the efficiency of the simple milling process to impose the notable Vis-light activity. It has been interpreted that Vis-light-excited RhB loses electrons to the surface hydroxyl group more suitably to form RhB+, while dissolved oxygen takes electrons more suitably to form an O2−
• O2−
• radical, thereby yielding the notable Vis-light photocatalytic activity by the surface photosensitization.