Characterization and improved solar light activity of vanadium doped TiO₂/diatomite hybrid catalysts

Highlights: • V-doped TiO₂/diatomite composite photocatalyst was synthesized. • The physiochemical property and solar light photoactivity were characterized. • The presence and influence of V ions in TiO₂ matrix was systematically analyzed. • The photocatalysis for Rhodamine B were studied under solar light illumination. - Abstract: V-doped TiO₂/diatomite composite photocatalysts with different vanadium concentrations were synthesized by a modified sol–gel method. The diatomite was responsible for the well dispersion of TiO₂ nanoparticles on the matrix and consequently inhibited the agglomeration. V-TiO₂/diatomite hybrids showed red shift in TiO₂ absorption edge with enhanced absorption intensity. Most importantly, the dopant energy levels were formed in the TiO₂ bandgap due to V⁴⁺ ions substituted to Ti⁴⁺ sites. The 0.5% V-TiO₂/diatomite photocatalyst displayed narrower bandgap (2.95 eV) compared to undoped sample (3.13 eV) and other doped samples (3.05 eV) with higher doping concentration. The photocatalytic activities of V doped TiO₂/diatomite samples for the degradation of Rhodamine B under stimulated solar light illumination were significantly improved compared with the undoped sample. In our case, V⁴⁺ ions incorporated in TiO₂ lattice were responsible for increased visible-light absorption and electron transfer to oxygen molecules adsorbed on the surface of TiO₂ to produce superoxide radicals ·O₂^–, while V⁵⁺ species presented on the surface of TiO₂ particles in the form of V₂O₅ contributed to e^––h⁺ separation. In addition, due to the combination of diatomite as support, this hybrid photocatalyst could be separated from solution quickly by natural settlement and exhibited good reusability