Highly efficient visible-driven reduction of Cr(VI) by a novel black TiO2 photocatalyst

Finding a facile and practical method to produce black TiO2 remains a challenge. Bismuth-vanadium co-doped black TiO2 (BVBT) was synthesized as a visible light driven photocatalyst by a simple one-pot hydrothermal method. The synthesized BVBT was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), UV-vis diffuse reflectance spectroscopy (UV-Vis DRS). The light absorption of the synthesized Bi-V co-coped black TiO2 nanoparticles was significantly improved in the visible and infrared regions. The XRD patterns indicated that the black TiO2 contained mixed phases of brookite, anatase, and rutile of TiO2. This was further confirmed by Raman spectroscopy. The photocatalytic activity of the sample was evaluated by reduction of hexavalent chromium (Cr(VI)) under visible light irradiation. Among investigated hole (h+) scavengers, ethylenediaminetetraacetic acid (EDTA) led to the highest reduction of Cr(VI) with a molar ratio of 1:5 (EDTA:Cr(VI)). The results indicated that the Bi-V co-coped black TiO2 nanocomposite can reduce 94% of 1 mg/L of Cr(VI) within 20 min irradiation time (pH 3 and catalyst dose of 1 g/L). Introducing a simple method to synthesize black TiO2 which has absorption in the visible and infrared region can open up new applications.