Understanding the doping mechanism of Sn in TiO 2 nanorods toward efficient photoelectrochemical performance

Doping metal ions into titanium dioxide (TiO 2 ) is an effective strategy toward the goal of high-performance photoelectrochemical (PEC) water splitting. Understanding the doping mechanism is crucial for tailoring the intrinsic properties of doped TiO 2 . In this study, we synthesized tin (Sn)-doped TiO 2 nanorods using a hydrothermal method and aim to understand the doping mechanism of Sn into TiO 2 for enhancing its PEC performance. The experimental results based on the morphological and structural analysis confirm the success of Sn doping into TiO 2 in which the dopant is homogeneously distributed in the structure of the nanorods. Density functional theory calculation combined with thermodynamic analysis provides clear evidence for the doping mechanism of Sn into TiO 2 crystal lattice. These results indicate that Sn dopant enters the rutile TiO 2 lattice as a substitute for Ti site and while the substituted Sn does not induce any localized state within the band gap of TiO 2 , it gives a significant amount of its valence electron to conduction, thereby helping to improve the photocatalytic activity. Compared with the TiO 2 nanorods sample, the Sn-doped TiO 2 nanorods sample shows highly efficient PEC performance, where its photocurrent density is significantly improved to 4.2 mA/cm 2 with a high photoconversion efficiency of 2.1%. Our results may afford a better understanding of the doping mechanism of Sn in TiO 2 and thus suggest that Sn-doped TiO 2 can serve as a potential photocatalyst material for a variety of solar energy-driven applications. Graphical Abstract