TiO 2 hollow sphere was synthesized by hydrothermal method using trifluoroacetic acid (TFA) and Ti(SO 4 ) 2 as raw materials, and it was applied to photocatalytic oxidization of elemental mercury (Hg 0 ) in the simulated flue gas. The prepared samples were well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (UV-vis DRS) and nitrogen adsorption/desorption. The results showed that only anatase phase TiO 2 hollow sphere was obtained. The average diameter of TiO 2 hollow spheres was about 800 nm and the shell thickness was about 200–400 nm. When M , the molar ratio of TFA to Ti(SO 4 ) 2 , was higher than a certain value, the photocatalytic activity of prepared TiO 2 hollow spheres began to reduce. When M = 2, addition TFA content was the best quantity, which got the best TiO 2 hollow spheres and provided the most appropriate F − decomposed from TFA during the sample preparation, which was helpful to its photocatalytic ability. In the experimental temperature range, the photocatalytic oxidation efficiency decreased with the increasing of reaction temperature, and the intensity of UV irradiation had an important effect on the photocatalytic reaction. When UV irradiation intensity was 303.45 μW cm −2 and reaction temperature was 55 °C, TiO 2 hollow sphere sample prepared at M = 2 had the highest photocatalytic ability and the mercury removal efficiency reached up to 82.75%.
Template-free method is used to facilely synthesize TiO 2 hollow microspheres via one-step hydrothermal method. Interestingly, the TiO 2 hollow microspheres have porous shell with thickness of about 450 nm. The formation mechanism of the hollow@porous TiO 2 microspheres involves the formation and aggregation of TiO 2 nanoparticles followed by oriented growth, etching of HF, and then Ostwald ripening and transformation process. The prepared TiO 2 microspheres show a reversible capacity of ~170 mAh g −1 after 150 cycles at a current density of 0.6 C and also exhibit a good rate capability of 40.8 mAh g −1 at a current density of 24 C due to the unique hollow@porous structure, which can offer more sites for the storage and insertion of Li ions, and accelerate electrolyte diffusion and Li ions transport. The results also indicate that the as-prepared TiO 2 material possesses excellent electrochemical performances, which may be an ideal anode material for lithium ion battery.
C/Ti 3 C 2 /(001)TiO 2 hollow microspheres were prepared by combining the template method, self-assembly and hydrothermal method . Anatase TiO 2 nanosheets with rich oxygen vacancies formed on the microspheres and exposed active (001) facets due to the spherical surface. TC was removed 92.3% by C/Ti 3 C 2 /(001)TiO 2 -HMs within 160 min, 28.4% by TiO 2 and 49.5% by (001)TiO 2 /Ti 3 C 2 under the same condition. The high removal efficiency of C/Ti 3 C 2 /(001)TiO 2 -HMs could be because the oxygen vacancies exposed on the surface of (001)TiO 2 afforded more active sites, extended the light absorption range and promoted the generation of electron-hole pairs. The composite C/Ti 3 C 2 /(001)TiO 2 structure could suppress the recombination of electron-hole pairs and prolong their lifetime. The degradation pathway of TC was discussed. The TC removal efficiency of C/Ti 3 C 2 /(001)TiO 2 -HMs was confirmed by treating the wastewater from the Slender West Lake. The production principle of oxygen vacancy could be used for preparing MXene composites with excellent catalytic properties and the C/Ti 3 C 2 /(001)TiO 2 -HMs could be a potential choice for treating wastewater.
Kai Wei,Kexin Li,Liushui Yan,Shenglian Luo,Huiqin Guo,Yuhua Dai,Xubiao Luo
In this paper, graphitic carbon nitride nanosheets/titanium dioxide hollow microspheres heterojunctions (g-C 3 N 4 NSs/TiO 2 HMSs) with excellent photocatalytic activity were successfully fabricated by a simple one-step synthesis strategy in the assistance of hydrothermal carbon microspheres. Hydrothermal carbon microspheres act as both dispersant and structure-directing agent for the simultaneous construction of graphitic carbon nitride nanosheets and titanium dioxide hollow microspheres. The synergistic photocatalytic effects in the 4-fluorophenol/hexavalent chromium [4-FP/Cr(VI)] and hexavalent chromium/trivalent arsenic [Cr(VI)/As(III)] multi-component composite pollution systems were studied by using as-prepared g-C 3 N 4 NSs/TiO 2 HMSs under different pH conditions. Interestingly, the efficiencies of 4-FP degradation, Cr(VI) reduction, and As(III) oxidation were simultaneously improved in the 4-FP/Cr(VI) and Cr(VI)/As(III) multi-component synergistic photocatalytic systems relative to the single-component photocatalytic systems. The synergistic photocatalytic mechanisms in the 4-FP/Cr(VI) and Cr(VI)/As(III) multi-component synergistic photocatalytic systems were systematically discussed.
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