| To date, TiO2 is coming a hot research topic of green environmental protection technology due to low cost, good chemical stability, non-toxic, high catalytic activity, resistance to corrosion and high quantum efficiency. However, pure TiO2 can only absorb less than 387.5 nm wavelength ultraviolet light because of its wide band gap(Eg=3.2 eV), and the UV spectrum only accounts for about 4% of the solar spectrum. Therefore, in order to make TiO2 photocatalytic technology move truly towards practical application, it is necessary that its absorption wavelength range be widened to visible light area. Existing studies have found that,proper doping of TiO2 nanomaterials or surface modification such as non-metal ion doping, metal ions modification and noble metal, metal ions modified can enhance the absorption of visible light, and effectively restrain the recombination of photogenerated electrons and holes, thus improve the visible light catalytic activity. According to this goal, in this article, TiO2 photocatalytic materials including nano-powders, nanotubes were prepared by sol-gel method, homogeneous precipitation method and anodic oxidation method. TiO2 photocatalytic materials was modified by non-metal B, S and noble metal Ru. The photocatalytic activities of the materials were discussed by photocatalytic degradation of methyl ene blue, and then the photoelectrocatalytic kinetic equation of a certain better material in degradation of methylene blue (MB) was established. Field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy (Raman), thermogravimetric analysis-differential thermal analysis (TG-DTA), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FT-IR), and UV-Vis spectrophotometer techniques were used to analyse and characterize the morphology, phase composition and thermal physical properties, element composition and chemical states, surface functional groups and the optical properties and other aspects of the materials. The main results are as follows:(1) Undoped TiO2, Ru/TiO2, B/TiO2 and B/Ru/TiO2 powders were prepared by the sol-gel method. The results showed that B occupy the TiO2 lattice gap to form B-O-Ti bonds, and partial B loaded on the surface of TiO1 grain to form B2O3; B, Ru doping could introduce hydroxyl groups on the surface of TiO2, making TiO2 acquiring more activity, and B doping could introduce more hydroxyl than Ru doping; The optimum preparation process and photocatalytic activity of the powder samples (2 h degradation) were obtained:TiO2, optimal calcining temperature of 500℃, 76.89%; Ru/TiO2, Ru doped with 0.005%, optimal calcining temperature of 500℃ and 72.80%; B/TiO2,B doped with 1%, optimal calcining temperature of 650℃ and 93.40%; B/Ru/TiO2, Ru doped with 0.005%, B doped with 1%, optimal calcining temperature of 600℃ and 80.84%. Comparison with the commercial TiO2-P25(65.46%), photocatalytic activity of the samples was improved in varying degrees under the same photocatalytic conditions.(2) S-doped TiO2 nano-powders were prepared by homogeneous precipitation method. The photocatalytic activities of the powders were evaluated according to their photodegradation behavior of methylene blue under visible light. The results indicated that the obtained powders were uniform with particle size about 20 nm.Partial S atoms occupy O sites in the TiO2 lattice to form Ti-O-S bonds, and the sulphur content was about 0.1 at.%. The structure of all the powders were anatase at the calcination temperature of 350～600℃, and the grain growth was increasingly complete with the increase of calcination temperature. In addition, the S-doped TiO2 nano-powders had a fairy visible photocatalytic activity. Under 18 W white fluorescent lights, the samples, calcinated at 550℃, degradated methylene blue in 2 h, corresponding the degradation rate of 80.67%. Comparison with the commercial TiO2-P25(65.46%), photocatalytic activity of the samples was increased by nearly 15%.(3) In the inorganic fluoride solution, RuO2 loaded TiO2 nanotube arrays were fabricated by anodic oxidation method combined with impregnation on pure titanium substrate sheet. The results showed that RuO2/TiO2 nanotubes remain the structural characteristics of the pure TiO2 nanotubes. Some of Ru ions were incorporated into the TiO2 lattice to form a solid solution by substituting Ti, while others were existed as RuO2 nanoparticles. The absorption light wavelength redshift was observed for RuO2/TiO2 nanotubes, and their optical absorption ability was enhanced in the entire visible region as compared to pure TiO2 nanotubes. The 4 h photoelectrocatalysis degradation rate against methylene blue increased from 27% for pure TiO2 nanotubes to 79% for RuO2TiO2 ones. The recycling process for the prepared nanotubes array film in this work is simple, and their photoelectrocatalysis degradation ability is basically unchanged after using 20 times. In the photoelectrocatalytic oxidation system, the optimal degradation parameters were as follows:the initial concentration of MB was 10 mg/L, the initial pH value was 2.11, the applied DC voltage value was 2.5 V and the concentration of applied electrolyte was 0.10 mol/L.The reaction of photoelectrocatalytic degradation was well fitted to the first-order reaction kinetic characteristics, which could be described by Langmuir-hinshelwood kinetic model. The kinetic equation was C=Coexp(-0.0998Co03901[-1gH+]-0.1998E1.7405cel04669t).(4) In the organic fluoride solution, RuO2/TiO2 nanotube arrays photocatalyst were fabricated by anodic oxidation method combined with impregnation. The results showed that Ru existed in the form of RuO2 disperse uniformly on the surface of TiO2 nanotubes, and the crystal structure of TiO2 nanotube was not changed by the load of RuO2; the load of RuO2 was conducive to the promotion of active groups Ti-OH on the surface of TiO2 nanotubes; the best impregnation concentration of ruthenium chloride solution is 0.0030 mol/L, RuO2TiO2 nanotube arrays, obtained under the impregnation concentration, got the best visible light catalytic activity. The 2 h photocatalysis degradation rate against methylene blue increased from 38% for pure TiO2 nanotubes to 69% for RuO2/TiO2 ones. This study thought that RuO2/TiO2 nanotube array had better photocatalytic properties, mainly because the RuO2 capture of hole promoted the effective separation of the RuO2/TiO2 nanotube composites photoproduction electronic-hole, to improve the service life of carrier, and increased the TiO2 nanotube surface hydroxyl oxygen adsorption. |
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