Effects of S Doping and Oxygen Vacancy on the Physical Properties of Rutile TiO₂ for Photocatalysis Applications...

This study explores the effects of sulfur (S) doping and oxygen vacancy (OV) creation on the fundamental properties of TiO₂, which plays a crucial role in photocatalysis applications. Using density functional theory (DFT + U), we investigate how S doping and OV impact the structural, electronic, mechanical, and optical properties of rutile TiO₂. The structural results reveal that the lattice constants of undoped rutile TiO₂ are a = b = 4.63 Å and c = 2.98 Å, which are consistent with reported values. Upon S doping at concentrations of 6.25%, 12.5%, and 18.75%, the lattice constants expand to a = b = 4.89 Å, 5.14 Å, and 5.31 Å, and c = 3.27 Å, 3.69 Å, and 3.82 Å, respectively. This expansion is attributed to the difference in atomic radii between sulfur and oxygen atoms. In contrast, the presence of OV leads to a reduction in the lattice constants, with values of a = b = 4.17 Å and c = 2.82 Å. Our findings on the electronic properties indicate that both S doping and OV contribute to an improvement in the electronic structure, notably shifting the electronic bandgap toward the visible spectrum. Moreover, the mechanical properties show that S doping increases the material's rigidity, while the introduction of OV results in a reduction of mechanical strength. This highlights a trade-off between improved photocatalytic activity and material durability. Lastly, the optical properties exhibit a red-shift in absorption due to S doping and the formation of OV, offering valuable insights for designing efficient photocatalysts for visible-light-driven applications.