Application of N-F-Codoped TiO2 for the Photocatalytic Reduction of Cr(VI) under Visible Light Irradiation

The visible light responsive N-F-codoped TiO₂ (hereafter denoted as NFT) was prepared by sol-gel method using NH₄F as precursor. NFT powders were characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and ultraviolet-visible diffuse reflection spectroscopy (UV-Vis-DRS). The as-prepared NFT powders could efficiently reduce Cr(VI) to Cr(III)under visible light irradiation. The photocatalytic activities of NFT on the reduction of Cr(VI) was found to be strongly dependent on pH and the initial concentration of dopant. At low pH, the reduction efficiency was high. The activity increased firstly with the increase of initial dopant concentration and then decreased gradually. The highest activity was achieved when the initial NH₄F /Ti molar ratio was 3. Moreover, addition of hole scavengers can greatly enhanced the Cr(VI) reduction rate due to synergistic effect. This study demonstrates a facile, fast and reproducible synthesis method for visible light responsive NFT photocatalyst and a potential way for environmental cleanup.