Baoshun Liu

Low temperature fabrication of V-doped TiO2 nanoparticles, structure and photocatalytic studies

V-doped TiO(2)nanoparticles were synthesized at low temperature and characterized by X-ray diffraction (XRD), Raman spectroscopy (RS), transmission electron microscopy (TEM), Brunauer-Emmet-Teller (BET), X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, and photoluminescence (PL) spectroscopy, respectively. It is found the nanoparticle shape changed from needle, to short stick and then to cubic with the increase of doped V concentration, which was also accompanied by the improvement of crystallinity. The specific surface area (S(BET)) decreased with increasing V content. It is confirmed that V ions can be doped in TiO(2) by substituting Ti(4+) ions, which suppressed the CB --> VB and surface recombination of photoinduced electrons and holes, and a relation was found between the PL spectra and the UV photocatalytic activity. There was an optimum V content for the V-doped TiO(2) to present the best UV-light induced photoactivity, but they were visible-inactive. At last, the effect of the doping V as trapping centers on photocatalysis was investigated in detail, and used to explain the difference between the photocatalysis under the illumination of UV light and visible light.

Mesoporous TiO2 Core–Shell Spheres Composed of Nanocrystals with Exposed High-Energy Facets: Facile Synthesis and Formation Mechanism

A facile new method that combines electrospray and hydrothermal treatment is used to prepare mesoporous core-shell TiO(2) spheres with high specific surface areas and high pore volumes. Interestingly, the resulting TiO(2) spheres are composed of anatase TiO(2) nanocrystals with exposed step-like {001} and smooth {010} facets. The percentage of exposed {001} facets can be adjusted by changing the experimental parameters used in the electrospray and hydrothermal treatment processes, such as the contents of poly(N-vinyl-2-pyrrolidone) and acetic acid. The combination of high specific surface area (>100 m(2) g(-1)), high pore volume (>0.30 cm(3) g(-1)), useful pore size (10-15 nm), spherical core-shell structure, and exposed high energy facets makes these TiO(2) spheres an important candidate for use in many photoelectrochemical applications. The formation mechanism of the mesoporous TiO(2) spheres is also studied. The great advantage of this method is that interesting and complicated mesoporous superstructures can be prepared using electrospray technology.

Hierarchical TiO2 spherical nanostructures with tunable pore size, pore volume, and specific surface area: facile preparation and high-photocatalytic performance

Anatase TiO2 hierarchical nanostructural microspheres with tunable pore size, pore volume, and specific surface area were prepared by a facile two-step method of electrospray and hydrothermal treatment. Compared to the calcination, the hydrothermal treatment can transfer the electrosprayed TiO2 microspheres to porous hierarchical nanostructures. Adding ammonia in the hydrothermal process has a great effect on the pore structure of TiO2 microspheres. The hydrothermal-treated samples with >2.0 ml ammonia being added are composed of both big and small nanocrystals. Some of the large nanocrystals grow in the [001] direction and contain step-like {101} surfaces. The large nanoparticles are formed through the combination of small particles by dehydration, which finally leads to the change of TiO2 microspheres from mesoporous to large-porous structure. The effects of the specific surface area, the pore volume, and the pore size on the photocatalytic activity are studied. It is considered that the pores on the surface layer of TiO2 microspheres are like a door that can control the diffusion of reactants between the outside and the inside. If the size of pores on the surface is big enough to allow the fast diffusion of reactants, the photocatalytic activity will increase with the increase of specific surface area and pore volume. In addition, further calcination on the TiO2 spheres after hydrothermal treatment can increase the photocatalytic activity, which is better than the commercial P25.

Synthesis, Characterization, and Photocatalysis of Fe-Doped : A Combined Experimental and Theoretical Study

Fe-doped TiO2 was prepared by hydrothermal treating Ti peroxide sol with different amount of iron nitrate. Fe ions can enter TiO2 lattice by substituting Ti4

Polymeric Adsorption of Methylene Blue in TiO2 Colloids—Highly Sensitive Thermochromism and Selective Photocatalysis

The polymeric adsorption of methylene blue (MB) on a TiO(2) surface is reported. The MB molecule on the TiO(2) surface mainly exists as the H-trimeric adsorption state, which results in the MB@TiO(2) polymeric sol. The trimeric adsorption leads to a remarkable blueshift of visible-light adsorption of MB. Electrostatic attraction is important for trimeric adsorption of MB on TiO(2) surfaces. The trimer-monomer equilibrium is highly sensitive on temperature changes, showing an interesting reversible thermochromism. The MB@TiO(2) polymeric sol can be photodegraded under UV illumination without destroying the equilibrium of trimer-monomer. Compared with anionic methyl orange, the TiO(2) colloid hydrosol shows highly selective photocatalysis of MB and other cationic dyes, including crystal violet, methylene green, and victoria blue B. The MB@TiO(2) polymeric sol is stable under visible-light illumination because interfacial transfer of electrons does not exist between MB and TiO(2).

Facile synthesis of transparent superhydrophobic titania coating by using soot as a nanoimprint template

This paper develops a robust method for the facile synthesis of transparent superhydrophobic TiO2 film by using the flame soot layer as a nanoimprint template. After the nanoimprint and calcination process, the TiO2 coating exhibited the inverse roughness structure of the soot layer with high transparent properties. And subsequent hydrophobic modification with 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FAS) rendered the transparent surfaces superhydrophobic (168 ± 4° for water). The transparency and superhydrophobicity of the TiO2 coating could be controlled by adjusting the initial concentration of the TiO2 suspension. The coating possesses excellent chemical stabilities and good mechanical resistance. Moreover, a superhydrophobic–superhydrophilic micropattern was further fabricated by illumination with ultraviolet light through a photomask. This fabrication process is expected to be extended to other transparent superhydrophobic coatings and to be used in many research fields.

Investigation of Electron Behavior in Nano‐TiO2 Photocatalysis by Using In Situ Open‐Circuit Voltage and Photoconductivity Measurements

The in situ open-circuit voltages (Voc ) and the in situ photoconductivities have been measured to study electron behavior in photocatalysis and its effect on the photocatalytic oxidation of methanol. It was observed that electron injection to the conduction band (CB) of TiO2 under light illumination during photocatalysis includes two sources: from the valence band (VB) of TiO2 and from the methanol molecule. The electron injection from methanol to TiO2 is slower than that directly from the VB, which indicates that the adsorption mode of methanol on the TiO2 surface can change between dark and illuminated states. The electron injection from methanol to the CB of TiO2 leads to the upshift of the Fermi level of electrons in TiO2 , which is the thermodynamic driving force of photocatalytic oxidation. It was also found that the charge state of nano-TiO2 is continuously changing during photocatalysis as electrons are injected from methanol to TiO2 . Combined with the apparent Langmuir-Hinshelwood kinetic model, the relation between photocatalytic kinetics and electrons in the TiO2 CB was developed and verified experimentally. The photocatalytic rate constant is the variation of the Fermi level with time, based on which a new method was developed to calculate the photocatalytic kinetic rate constant by monitoring the change of Voc with time during photocatalysis.

Electrospinning preparation and photocatalytic activity of porous TiO 2 nanofibers

Porous TiO2 nanofibers were prepared via a facile electrospinning method. The carbon nanospheres were mixed with the ethanol solution containing both poly(vinylpyrrolidone) and titanium tetraisopropoxide for electrospinning; and subsequent calcination of as-spun nanofibers led to thermal decomposition of carbon nanospheres, leaving behind pores in the TiO2 nanofibers. The morphology and phase structure of the products were investigated with scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Furthermore, the photocatalytic activity of porous TiO2 nanofibers was evaluated by photodecomposition of methylene blue under UV light. Results showed that the porous TiO2 nanofibers have higher surface area and enhanced photocatalysis activity, compared to nonporous TiO2 nanofibers.

A stochastic study of electron transfer kinetics in nano-particulate photocatalysis: a comparison of the quasi-equilibrium approximation with a random walking model

In the photocatalysis of porous nano-crystalline materials, the transfer of electrons to O2 plays an important role, which includes the electron transport to photocatalytic active centers and successive interfacial transfer to O2. The slowest of them will determine the overall speed of electron transfer in the photocatalysis reaction. Considering the photocatalysis of porous nano-crystalline TiO2 as an example, although some experimental results have shown that the electron kinetics are limited by the interfacial transfer, we still lack the depth of understanding the microscopic mechanism from a theoretical viewpoint. In the present research, a stochastic quasi-equilibrium (QE) theoretical model and a stochastic random walking (RW) model were established to discuss the electron transport and electron interfacial transfer by taking the electron multi-trapping transport and electron interfacial transfer from the photocatalytic active centers to O2 into consideration. By carefully investigating the effect of the electron Fermi level (EF) and the photocatalytic center number on electron transport, we showed that the time taken for an electron to transport to a photocatalytic center predicated by the stochastic RW model was much lower than that predicted by the stochastic QE model, indicating that the electrons cannot reach a QE state during their transport to photocatalytic centers. The stochastic QE model predicted that the electron kinetics of a real photocatalysis for porous nano-crystalline TiO2 should be limited by electron transport, whereas the stochastic RW model showed that the electron kinetics of a real photocatalysis can be limited by the interfacial transfer. Our simulation results show that the stochastic RW model was more in line with the real electron kinetics that have been observed in experiments, therefore it is concluded that the photoinduced electrons cannot reach a QE state before transferring to O2.

一种可见光活性的等离子体纳米Au-Cu(I)@Na 2 Ti 6 O 13 光催化滤膜的制备和对乙醛的降解

Abstract The present article reports a novel self-standing nanostructured Au-Cu(I)@Na2Ti6O13 plasmonic photocatalytic membrane, which is prepared by a hydrothermal reaction followed by a simple subsequent heat treatment process. The morphological structure, elemental composition, crystalline phases, and optical properties of the membrane were studied in detail by field-emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and ultraviolet-visible spectroscopy. Compared with that of a pure Na2Ti6O13 membrane, the Au-Cu(I)@Na2Ti6O13 membrane displayed much higher photocatalytic activity for the decomposition of acetaldehyde, a typical volatile organic compound, under visible light illumination. It was found that the photocatalytic activity of the Au-Cu(I)@Na2Ti6O13 membrane increased as the amount of Au was increased. The membrane loaded with 2.85 wt% Au showed the highest photocatalytic activity in the decomposition of acetaldehyde of the investigated materials. We found that in the photocatalyst membrane, Na2Ti6O13 acted as a support material, Au displayed plasmonic absorption, and Cu(I) behaved as a co-catalyst. The present membrane materials can avoid the self-aggregation typically observed during the course of photocatalytic reactions. As a result, they can be easily separated, recycled, and reactivated after their practical application, making these functional materials attractive for use in air cleaning applications.