Constructing a tunable defect structure in TiO2 for photocatalytic nitrogen fixation
The photocatalytic system capable of precisely regulating oxygen vacancies (OVs) concentration which could help illuminate the effect of OVs concentration on N2 fixation activity are still scarce. Here, we demonstrate that the excessive OVs in TiO2, while increasing the adsorption activation capacity of N2 molecules, exhibits disappointing activity due to a decrease in charge separation efficiency. With the optimized OVs concentration, TiO2 can increase the charge separation efficiency by 3 times and hold a significant activation towards N2 molecules. The normalized N2 photofixation rate is 324.86 μmol•h-1•g-1 (full spectrum) and the corresponding apparent quantum yield (AQY) under 365 nm reaches 1.1%, which are at a relatively high level among the literature report. The origin of this excellent activity is clearly attribute to the OV defect structures, which coordinates the charge separation efficiency and the dissociative adsorption capacity of N2. This work establishes the relationship between OVs concentration and activity, and helps to construct a highly efficient nitrogen-fixing photocatalyst by optimizing the OVs concentration.