DFT study of TiO₂ brookite (210) surface doped with silver and molybdenum

Abstract

The most popular semiconductor in dye-sensitized solar cells (DSSCs) is titanium dioxide (TiO2) because of its low cost, non-toxicity, and good stability. However, the DSSCs still have low efficiency due to the low light absorption of TiO2 in the visible region. Understanding the properties of TiO2 can contribute to improving the efficiency of DSSCs. In this study, we use density functional theory to investigate the electronic and optical properties of TiO2 brookite (210) surface mono-doped and co-doped with 4d transition metals, silver, and molybdenum. Our results show that the band gap energy of brookite (210) surface is 3.514 eV, which reduces to 1.143 eV and 0.183 eV when doped with Ag and Mo, respectively. However, doping with both Ag and Mo yielded a band gap of 0.387 eV. The results suggest the presence of Ag and Mo 4d states below the conduction band minimum, which could be responsible for the narrowing of the band gap on brookite (210) surface. Both mono-doped and co-doped brookite (210) surfaces have higher visible light absorbance compared to the undoped brookite (210) surface and extends to the near-infrared region.

Mechanistic Understanding in Manipulating Energetics of TiO2 for Photocatalysis

“…A composite catalyst of Cu 3 P-g-C 3 N 4 nano-heterojunctions with TiO 2 can produce synergistic effects in photocatalytic H 2 generation. Multilayer p-n and n-n heterojunctions are effective methods to enhance photocatalysis, as they have built-in electric and/or magnetic fields. − Magnetic Fe 3 O 4 –TiO 2 composites provide an added benefit of the separation of photocatalysts using an external magnetic field after the reaction is done. , Moreover, for a complete understanding of the process and reaction mechanisms, the photoactivity of doped/co-doped TiO 2 by transition metals or nonmetals needs to be studied more by computer simulation, such as a simulation by density functional theory (DFT) ,− or first-principles study, to identify the nature of the crystal structure, defects, stabilization, charge separation and compensation, and optical absorption coefficients. More theoretical studies such as WO 3 /WO 3 and WO 3 /TiO 2 heterojunctions should be conducted to calculate interfacial energies of different heterojunctions to determine their structure–property relationships and tune nanostructure morphology.…”

“…Pure single-crystalline and rhombohedral TiO 2 NPs with exposed {001} facets are recently found to have lower defect density and high electron mobility that can be employed to enhance photocatalysis . Various binary and ternary co-doping (such as Zn and Mg-doped TiO 2 , Zn and V-doped TiO 2 , Fe–Pr co-doped TiO 2 , Zr–Y co-doped TiO 2 , Ag–Mo co-doped TiO 2 , W–Mo–V-doped TiO 2 , Fe–Nd and Cd–Nd co-doped TiO 2 , Fe/Ce/La-doped TiO 2 , ) of TiO 2 also synthesized for enhanced photocatalytic activity as they produce a remarkable reduction in TiO 2 bandgap. Doped TiO 2 in porous platforms is another area, where immense interest exists for photocatalytic water purification. , …”