Combinatorial doping of TiO₂ with platinum (Pt), chromium (Cr), vanadium (V), and nickel (Ni) to achieve enhanced photocatalytic activity with visible light irradiation

Titanium dioxide (TiO₂) was doped with the combination of several metal ions including platinum (Pt), chromium (Cr), vanadium (V), and nickel (Ni). The doped TiO₂ materials were synthesized by standard sol-gel methods with doping levels of 0.1 to 0.5 at.%. The resulting materials were characterized by x-ray diffraction (XRD), BET surface-area measurement, scanning electron microscopy (SEM), and UV-vis diffuse reflectance spectroscopy (DRS). The visible light photocatalytic activity of the codoped samples was quantified by measuring the rate of the oxidation of iodide, the rate of degradation of methylene blue (MB), and the rate of oxidation of phenol in aqueous solutions at λ > 400 nm. 0.3 at.% Pt-Cr-TiO₂ and 0.3 at.% Cr-V-TiO₂ showed the highest visible light photocatalytic activity with respect to MB degradation and iodide oxidation, respectively. However, none of the codoped TiO₂ samples were found to have enhanced photocatalytic activity for phenol degradation when compared to their single-doped TiO₂ counterparts.