Rapid proton exchange between surface bridging hydroxyls and adsorbed molecules on TiO2

The rapid proton exchange between surface bridging hydroxyls and adsorbed molecules on TiO2 was investigated, which was modulated by surface healing. [Display omitted] •The interactions of adsorbed molecules with the surface sites on TiO2 were investigated.•The surface hydroxyls, defects and Ti sites were modulated by surface healing process.•The rapid proton exchange between the defect-involved bridging hydroxyl groups and the adsorbed molecules was confirmed.•The increase in non-defective surface sites enhanced ζ potential and hindered interfacial electron transfer activity. Understanding the interactions of adsorbed molecules with TiO2 surfaces is important for diverse applications, such as photocatalysis and self-cleaning surfaces. Herein, we investigated the interactions of adsorbed molecules with surface sites on TiO2. The 1H NMR spectra showed that surface healing led to an interesting upfield shift in the chemical shifts of hydroxyls of adsorbed molecules, which is caused by rapid proton exchange between the defect-involved bridging hydroxyls and adsorbed molecules. Infrared spectroscopy confirmed that surface healing decreases the number of surface hydroxyl groups and enhances the number of non-defective surface Ti sites required for methanol adsorption. Therefore, we proposed that undissociative adsorption of methanol is the preferential interaction mode with the non-defective sites of the TiO2 surface but dynamic equilibrium between dissociative and undissociative adsorption exists around surface defect sites. The increase in non-defective surface sites enhanced the surface ζ potential and hindered interfacial electron transfer activity.