Enhanced direct degradation of photogenerated holes induced by dissolved O2 chemisorbed on oxygen-deficient nano-TiO2

Due to the high electronegativity, dissolved O2 molecules can form strong chemisorption on oxygendeficient nano-TiO2, which can alter the photocatalytic degradation process. Regarding this point, there is a lack of sufficient investigation so far, although there have been many reports on oxygendeficient nano-TiO2. Here, we make the dissolved O2 adsorbed on the oxygen-deficient nano-TiO2 by simply stirring for a long time. The characterization and theoretical calculation results show that the chemisorption of O2 significantly enhances the surface hydrogen bonding and results in a substantial increase in the co-adsorbed H2O molecules and -OH groups. The co-chemisorbed oxygen species promote the separation of electron-hole pairs, meanwhile accelerate the migration and accumulation of holes to the surface, which effectively enhances the direct oxidation of photogenerated holes. The findings of this work suggest that for long continuous reactions, the role of chemisorbed dissolved O2 molecules on the photocatalytic degradation activity of oxygen-deficient nano-TiO2 has to be considered.(c) 2023 Elsevier Ltd. All rights reserved.