| Semiconductor photocatalysis has attracted wide attention on photodegradation of organic pollutants in recent decades. Among these semiconductor materials, TiO2 as photocatalyst has been widely used for its relatively high catalytic reactivity, nontoxicity, physical and chemical stability, and cost-effectiveness. However, the intrinsic defects of TiO2, such as low utilization rate of visible light and quantum yield efficiency, poor adsorbing affinity of target pollutants and the problem of separation and recovery, are major bottleneck drawbacks for its practical application.Based on the above research background, this paper mainly focuses on the synthesis of graphene/TiO2 Nanotube Arrays (GR/TNAs) and graphene/TiO2 fiber (GTF) by using electro-deposition method and Sol-gel-forcespinning method, respectively. The major contents of this thesis are summarized as follows:(1) Graphene/TiO2 Nanotube Arrays (GR/TNAs) photoelectrodes were fabricated by in-situ anodization and electro-deposition method. The surface morphology, structure, photoluminescence spectra (PL), and photocatalytic activity of the samples were investigated. The as-prepared graphene/TNAs (GR/TNAs) photoelectrodes showed significant improvement in the separation of photogenerated carriers and excellent photocatalytic stability, the removal efficiency was still as high as 75%after 10 cycles. The effects of irradiation time, initial concentration, ionic strength and bias potential on the removal of rhodamine B (Rh. B) by TNAs and GR/TNAs were studied systematically for the first time. The GR/TNAs exhibited significantly enhanced photocatalytic activity compared to unmodified TNAs. Results showed that after 60 min illumination at pH of 6.0, the degradation rate of Rh.B for GR/TNAs photoelectrodes reached 75%, which was 1.45 times higher than TNAs. NO3-, Ca2+ and Mg2+in the solution promoted the degradation of Rh.B, while SO42-, Cl" and F" suppressed the removal rate. When the bias potential was applied, Rh. B degradation rate increased to 90% at 0.5 V.(2) Titanium tetrabutoxide (TBOT) and ethyl acetoacetate (EAcAc) will be used as sources of titanium and chelating agent, respectively, and GO will be dispersed into the solvent, tetrahydrofuran (THF), by ultrasonic treatment. Dry centrifugal spinning method is going to be used to fabricate the fibers precursor, and then followed by water vapor annealing to make TiO2 crystalline phase form and GO be reduced at the same time. The addition of GO was changed to fabricate GTF with different content of graphene. The method has applied an invention patent, and got authorized by SIPO of China (No. ZL 201310064816.6). The as-prepared GTF was characterized by many instruments and technologies to confirm that GO was reduced and introduced into the fibers successfully. Compared with PTF, the Ti2p of 0.1 GTF made a red shift of 0.2 eV. The results showed that carbon atom was introduced into the lattice of Tid and the C-Ti bond was formed. In addition, there are oxygen vacancies and Ti3+on the surface of GTF.0.1 GTF possessed the biggest BET specific surface area (86.772 m2/g), nearly 2 times bigger than PTF. The introducing of graphene made the adsorption edge of GTF red shift, narrowed the band gap in the order of 0.1GTF (2.59 eV)< 0.05GTF (2.65 eV)< 0.025GTF (2.74 eV)< PTF (3.02 eV). The results of photocatalysis showed that GTF exhibited significantly enhanced photocatalytic activity compared to unmodified PTF. Results showed that after 30 min illumination of visible light, the degradation rate of X-3B for 0.1 GTF reached 98%, about 4 times higher than TNAs. Under the irradiation of UV light for 30 min, the photocatalytic efficiency of X-3B with 30 mg/L was higher than P25 by 10%. During the photocatalytic oxidation reaction, h+played the most important role in all the photo-induced reactive species. (3) Graphene/TiO2 fiber (GTF) photocatalysts were synthesized by a sol-gel combined with centrifugal force spinning process followed by calcining at 500℃in N2, steam and air, respectively. The synthesized catalysts contain only anatase phase, and N2-calcinated sample showed an obvious lattice distortion. Compared with GOTF-air and GOTF-N2, more oxygen-containing functional groups on GO in 0.1 GTF have been reduced. A hydrophilic surface can be observed in steam-and air-calcinated fiber due to the large amount of surface Ti-OH. For fiber obtained in steam, Ti 2p made a red shift of 0.2 eV to the lower bonding energy is observed, indicating the presence of Ti3+.0.1GTF possessed the biggest BET specific surface area and pore volume than GOTF-air and GOTF-N2. The photocatalytic results showed that 0.1 GTF exhibited highest photocatalytic activity and the degradation rate of X-3B (30 mg/L) almost reached 100% after 120 min under visible light irradiation, while the degradation rate of GOTF-air and GOTF-N2 was 63% and 42%, respectively. |
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