Oxygen vacancies induced by multi-valences of iodine in two-step hydrothermal synthesized I/TiO 2 with enhanced visible photoactivity.
A facile and efficient way of generating oxygen vacancies in visible light activated one-dimensional iodine doped TiO 2 photocatalysts was first reported in this work. A two-step hydrothermal synthesis was used to synthesize TiO 2 nanomaterials modified by iodic acid (HIO 3 ) as a dopant. Detailed analysis was conducted to illustrate the intrinsic doping/reaction mechanisms of iodic acid in the modification of the TiO 2 matrix. The phase and structure evolution were deduced from X-ray diffraction (XRD), Raman, and scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) was conducted to analyze the generation of oxygen vacancies and the formation of I–O–Ti bonds in the TiO 2 lattice. Multi-valences of iodine, due to the reduction of iodic acid, facilitated the generation of oxygen vacancies and 3d state Ti 3+ species in the TiO 2 lattice. The visible light absorption and enhanced photocatalytic activity of the TiO 2 nanomaterials were attributed to existing oxygen vacancies, iodine multi-valences in I–O–Ti bonds, and 3d state Ti 3+ sites in the TiO 2 lattice. The photocatalytic degradation efficiency under visible light ( λ > 400 nm) followed a pseudo first-order kinetic model. Rutile nanowires using a two-step synthesis method produced the highest methylene blue (10 mg L −1 ) degradation rate constant, K ap , of 7.92 × 10 −3 min −1 compared to other synthesized nanomaterials. The K ap value obtained was an order of magnitude greater than commercial P25 (3.87 × 10 −4 min −1 ) and pristine TiO 2 nanowires (4.18 × 10 −4 min −1 ). The iodine doped TiO 2 photocatalysts can be used in TiO 2 /light irradiation advanced oxidation processes (AOPs) in water treatment using sunlight or a visible light source, rather than an ultraviolet irradiation source.