Facile one-pot fabrication and high photocatalytic performance of vanadium doped TiO₂-based nanosheets for visible-light-driven degradation of RhB or Cr(VI)

Graphical abstract: - Highlights: • V-TNSs with high stability and recyclable usability were prepared by one-pot method. • Vanadium doping results in the changes in the structure, vacancy and red shift range. • Vanadium doping leads to obviously increase of the Ti³⁺ ions content. • Doped vanadium can effectively trap electrons to enhance the separation of charges. • V-TNSs exhibit excellent visible-light photoactivity for RhB solution or Cr(VI). - Abstract: Vanadium doped TiO₂-based nanosheets (V-TNSs) with different V/Ti ratios were prepared by a facile one-pot hydrothermal method using vanadium nitrate and P25 as the vanadium precursor and titanium precursor, respectively. The results indicated that as-synthesized photocatalysts exhibited sheet-like structure with large specific surface area (270–340 cm²/g) and small thickness (4–5 nm). XPS results revealed that vanadium exists in the form of V⁴⁺ and V⁵⁺, and the binding energies of Ti−O bonds have been changed with the concentration of vanadium. Vanadium doping resulted in considerable enhancement of visible light absorption, red-shift, and the band-gap of photocatalysts reduced from 3.18 eV to 2.91 eV. The density functional theory (DFT) calculations for band structure and total energy also provided a good explanation and further confirmation for the experimental results. It has been found that the photo-activity increased gradually with the concentration of vanadium, and then decreased after attaining a maximum with an optimal content of vanadium at 1.0 at.% for RhB or Cr(VI). The reaction rate K_app of 1.0%-V-TNSs are 9.27-fold and 3.26-fold as compared to undoped TNSs under UV–vis and visible light irradiation, respectively. The cyclic tests that performed six times demonstrated high stability and reusability of the photocatalysts. A possible alternate mechanism for the enhancement of the photocatalytic activity under visible-light irradiation was also proposed.