Enhanced photoactivity of Bi2WO6 by iodide insertion into the interlayer for water purification under visible light

An iodine intercalated Bi2WO6 was fabricated by a facile hydrothermal method (160 degrees C, 2 h) and characterized by field emission scanning electron microscope, high resolution transmission electron microscopy, nitrogen adsorption/desorption isotherms, X-ray diffraction and X-ray photoelectron spectroscopy, Fourier-transform infrared and UV-Vis diffuse reflectance spectra. The I-0.30-Bi2WO6 with an I/W molar ratio of 0.30 was highly effective for the degradation and mineralization of 2-chlorophenol, rhodamine B, bisphenol A, phenol, ciprofloxacin and sulfamethoxazole in water under visible light. Furthermore, the visible-light-driven photocatalytic activity of Bi2WO6 was enhanced 3.1 times by the introduction of I-. The characterized results indicated that I- mainly inserted into the interlayer of Bi2WO6, expanding the layer spacing, favoring the efficient charge separation and transfer and prohibiting the recombination of the photogenerated electrons and holes. Specially, the XPS analysis indicated the ions substitued the absorbed oxygen to chemically bond in the layered Bi2WO6, resulting in the change of the electric charge distribution of Bi2WO6. Moreover, the BET surface area was increased from 25.2 m(2) g(-1) for Bi2WO6 to 66.7 m(2) g(-1) for I-0.30-Bi2WO6 for more surface active sites. In addition, the band gap was narrowed for expanded optical absorption in the visible light region. ESA and radicals trapping experiments verified holes were the main active species for the degradation of organic pollutants. Simultaneously, the more positive potential of valence band in iodine intercalated Bi2WO6 could enhance the oxidative power of the photogenerated holes, resulting in the efficient removal of refractory organic pollutants in water.