Synthesis and photocatalytic property of the ZrO<Subscript>2</Subscript>/TiO<Subscript>2</Subscript> pillared laponite

The ZrO2/TiO2 pillared laponite (Ti-Zr-lap) photocatalysts were prepared with intercalation reaction by supercritical fluid drying (SCFD),and characterized by XRD,TEM,SEM and BET surface area analysis,and the photocatalytic properties of Ti-Zr-lap were investigated by degradation of azo dye acid red B (ARB).The results showed that the ZrO2/TiO2 pillared structures in laponite could be formed,with the mass fraction of (Zr4++Ti4+)/laponite (Xm) increasing,the basal spacing and the BET surface area of Ti-Zr-lap significantly increased.The Ti-Zr-lap used as photocatalyst had the advantages of stable and porous layered structure,large surface area with the anatase type TiO2.Compared with the Ti-Zr-lap dried by air drying,the Ti-Zr-lap dried by SCFD showed better photocatalytic property which was very close to that of P25 TiO2.Using the Ti-Zr-lap as photocatalyst with the optimum Xm of 0.16 and the calcination temperature of 500 ℃,under the conditions of the initial concentration of ARB 20 mg/L,photocatalyst concentration of 1.5 g/L and irradiation time 60 min,the decoloring rate of ARB could achieve 98.3%,indicating that the Ti-Zr-lap had excellent photocatalytic property.     

Hydrothermal preparation and photocatalytic water splitting properties of ZrW<Subscript>2</Subscript>O<Subscript>8</Subscript>

ZrW₂O₈ was prepared by adjusting Zr:W mole ratio and HCl concentration in hydrothermal reaction processes. The obtained sample was crystallized in α-ZrW₂O₈ phase (cubic, P2₁3), with band gap energy of 4.0 eV. The properties of photocatalytic water splitting were examined under UV light irradiation. The average rate of H₂ evolution over 0.3wt% Pt/ZrW₂O₈ in the presence of CH₃OH as electron donor (ED) was 23.4 μmol/h, while the average rate of O₂ evolution over ZrW₂O₈ in the presence of AgNO₃ as electron scavenger (ES) was 9.8 μ mol/h. Moreover, H₂ was evolved over 0.3wt% Pt/ZrW₂O₈ from pure water splitting at a rate of 5.2 μ mol/h. The study indicated that the band structure of ZrW₂O₈ was suitable for reducing H⁺ to H₂ and oxidizing H₂O to O₂. The band structure and photocatalytic water splitting properties of ZrW₂O₈, different from either ZrO₂ (5.0 eV) or WO₃ (2.7 eV), were attributed to the hybridization of W5d and Zr4d in conduction band (CB) as well as the change in crystal structure.     

Antibacterial properties of TiO<Subscript>2</Subscript> ceramic pellets prepared using nano TiO<Subscript>2</Subscript> powder

Titanium dioxide (TiO₂) porous ceramic pellets with three dimension nano-structure were prepared using nano TiO₂ powder. The TiO₂ porous ceramic pellets were composed of TiO₂ nanoparticles with 14–16 nm in diameter and had porosity of 74.85%. The mean pore size of the TiO₂ porous ceramic pellets was 20.73 nm and the main pore size ranged from 3 to 16 nm. The mass loss of the TiO₂ ceramic pellets was less than 5% after 20 d immersion in water. The antibacterial properties of the TiO₂ pellets were studied. The sterilization rate of Colibacillus (hospital polluted water with bacterium) can reach 99% after 3 h photocatalytic process and these TiO₂ pellets are easy to be re-activated and cyclically be used. The shaping mechanism and photocatalysis sterilization mechanism of the TiO₂ pellets were discussed. Funded by the Applied Basis Research from Sichuan Province, the Research of Photo Purification to Environment with Nano TiO₂ (No. 05YJ029-010)     

In-situ TEM Study on Mierostruetural Evolution of Nanostruetured TiO2

The effect of electron beam on the microstructures and phase transformation of nanostructured TiO2 heat treated at various temperatures for different time was studied by in-situ TEM and SAED. Anatase ex-situ heated at 250℃ and 360℃ transformed to rutile while irradiated by the electron beam. With the increasing sizes and distribution of the powders on the amorphous carbon, the process of phase transformation by the electron beam was encumbered. These evolutions may be due to the changes of vacuum atmosphere and the properties of powders.     

Synthesis and characterization of ultra-fine Cr<Subscript>2</Subscript>O<Subscript>3</Subscript> from hydrogen reduction of K<Subscript>2</Subscript>CrO<Subscript>4</Subscript>

As a part of the green process for manufacturing chromium compounds, two steps are involved in the synthesis of ultra-fine Cr2O3 powders： the first is the hydrogen reduction of K2CrO4 into intermediate trivalent （Cr^3＋） or tetravalent （Cr^4＋） chromium compounds; the second is the decomposing of the intermediate into Cr2O3 by heat treating. The intermediate is well characterized by means of SEM, XRD, and XPS. The possible reaction mechanism of the process is analyzed.     

Influence of rare earth co-dopant on the photocatalytic property of TiO<Subscript>2</Subscript> nano-particles

A series of nanometer TiO2 photocatalysts co-doped respectively with rare earth Er3+-Ce3+ and La3+-Fe3+ were prepared by sol-gel method,and the photocatalytic activity under ultra-violet light was evaluated by photocatalytic degradation of methyl blue.The crystallographic forms,particles size,and morphology were characterized by XRD and TEM.The results showed that the optimum heat temperature of co-doped TiO2 was 550 ℃,and the co-doped TiO2 kept anatase.The anatase crystal had the average size of 20 nm.The ...     

Effects of Nitrogen Doping on Microstructure and Photocatalytic Activity of Nanocrystalline TiO2 Powders

Nitrogen-doped TiO2 nanocrystalline powders were prepared by hydrolysis of tetrachloride titanium （TiCl4） in a mixed solution of ethanol and ammonium nitrate （NH4NO3） at ambient temperature and atmosphere followed by calcination at 400 ℃ for 2 h in air. FTIR spectra demonstrate that amine group in original gel is eliminated by calcination, and the TiO2 powder is liable to absorb water onto its surface and into its capillary pore. XRD and SEM results show that the average size of nanocrystalline TiO2 particles is no more than 60 nm and with increasing the calcination temperature, the size of particles increases. XPS studies indicate the nitrogen atom enters into the TiO2 lattice and occupies the position of oxygen atom. The nitrogen doping not only depresses the grain growth of TiO2 particles, but also reduces the phase transformation temperature of anatase to futile. The photocatalytic activity of the nitrogen-doped TiO2 powders has been evaluated by experiments of photocatalytic degradation aqueous methylene blue.     

Structural characteristics and photocatalytic activity of ambient pressure dried SiO<Subscript>2</Subscript>/TiO<Subscript>2</Subscript> aerogel composites by one-step solvent exchange/surface modification

An ambient pressure synthesis of SiO₂/TiO₂ binary aerogel was prepared through the low-cost precursors of titanium tetrachloride (TiCl₄) and sodium silicate (Na₂O·nSiO₂). After gelation, solvent exchange and surface modification were performed simultaneously and the modified gel was finally dried under ambient pressure. Microstructural analyses by transmission electron microscope (TEM) indicate that fabricated SiO₂/TiO₂ aerogel composite shows similar sponge-like nanostructure as silica aerogel, and the Brunauer–Emmett–Teller (BET) analysis shows that the specific surface area of the composite reaches 605 m²/g, and the average pore size is 9.7 nm. Such binary aerogel exhibits significant photocatalytic performance in this paper for treating model pollutant of methyl orange (MO), and the decolorizing efficiency of MO is detected as 84.9% after 210 mins exposure to UV light irradiation. Degraded gel suspends in the water so as to separate from solution for reuse, and after 4 times recycling, 70% degradation efficiency can be easily reached when composite catalyzed system is exposed for 210 mins under UV irradiation.     

Electronic band structures of TiO<Subscript>2</Subscript> with heavy nitrogen doping

The first-principles density-functional calculation was conducted to investigate the electronic band structures of titanium dioxide with heavy nitrogen doping （TiO2-xNx）.The calculation results indicate that when x≤0.25,isolated N 2p states appear above the valence-band maximum of TiO2 without a band-gap narrowing between O 2p and Ti 3d states.When x≥0.50,an obvious band gap narrowing between O 2p and Ti 3d states was observed along with the existence of isolated N 2p states above the valence-band of TiO2,indicating that the mechanism proposed by Asahi et al operates under heavy nitrogen doping condition.     

Synthesis and characterization of VO<Subscript>2</Subscript>/mesoporous carbon composites for hybrid capacitors

VO₂/ordered mesoporous carbon (CMK-3) composites were prepared by solid-state reaction process. The microstructures were characterized by X-ray diffraction (XRD), nitrogen adsorption and desorption, field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The experimental results showed that the vanadium oxide in the composites was vanadium dioxide (VO₂) with monoclinic structure, which was artificially loaded on the outer surface of CMK-3. VO₂/ordered mesoporous carbon composites present a significantly improved capacitive performance (131 F/g) increased by 40.86% compared to that of CMK-3 carbon (93 F/g). Therefore, as-prepared VO₂/mesoporous carbon composites suggest promising applications in hybrid capacitors.     

UV-vis and photoluminescent spectra of TiO<Subscript>2</Subscript> films

TiO₂ fims have been deposited on glass substrates using DC reactive magnetron sputtering at different oxygen partial pressures from 0. 10 Pa.to 0.65 Pa. The transmittance (UV-vis) and photoluminescence (PL) spectra of the films were recorded. The results of the UV-vis spectra show that the deposition rate of the films decreased at oxygen partial pressure P(O₂)≥0.15 Pa, the band gap increased from 3.48 eV to 3.68eV for direct transition and from 3.27 eV to 3.34 eV for indirect transition with increasing the oxygen partial pressure. The PL spectra show convincingly that the transition for films was indirect, and there were some oxygen defect energy levels at the band gap of the films. With increasing the O₂ partial pressure, the defect energy levels decreased. For the films sputtered at 0.35 and 0.65 Pa there were two defect energy levels at 2.63 eV and 2.41 eV, corresponding to 0.72 eV and 0.94 eV below the conduction band for a band gap of 3.35 eV, respectively. For the films sputtered at 0.10 Pa and 0.15 Pa, there was an energy band formed between 3.12 eV and 2.06 eV, corresponding to 0.23 eV and 1.29 eV below the conduction band. ZHAO Qing-nan : Born in 1963 Funded by Natural Science Foundation of Hubei Province, China.     

Characterization and photocatalytic activity of KSr<Subscript>2</Subscript>Nb<Subscript>5</Subscript>O<Subscript>15</Subscript> with tungsten bronze structure

Tungsten bronze (TB) type potassium strontium niobate KSr₂Nb₅O₁₅ was prepared by solid-state reaction method, and was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-vis diffuse spectrum. The photocatalyst shows high photocatalytic activity of photodegrading acid red G. The effects of photocatalyst dosage and initial concentration of acid red G on the photodegradation process were studied. The kinetics of photocatalytic degradation of acid red G by KSr₂Nb₅O₁₅ catalyst follows the first order reaction.     

Improved Breakdown Strength in (Ba<Subscript>0.6</Subscript>Sr<Subscript>0.4</Subscript>)<Subscript>0.85</Subscript>Bi<Subscript>0.1</Subscript>TiO<Subscript>3</Subscript> Ceramics with Addition of CaZrO<Subscript>3</Subscript> for Energy Storage Application

(Ba_0.6Sr_0.4)_0.85Bi_0.1TiO₃ ceramics doped with x wt%CaZrO₃ (x= 0-10) were synthesized by solid-state reaction method. The effects of CaZrO₃ amount on the dielectric properties and structure of (Ba_0.6Sr_0.4)_0.85Bi_0.1TiO₃ ceramics were investigated. X-ray diffraction results indicated a pure cubic perovskite structure for all samples and that the lattice parameter increased till x=5 and then slightly decreased. A homogenous microstructure was observed with the addition of CaZrO₃. Dielectric measurements revealed a relaxor-like characteristic for all samples and that the diffusivity γ reached the maximum value of 1.78 at x=5. With the addition of CaZrO₃, the dielectric constant dependence on electric field was weakened, insulation resistivity enhanced and dielectric breakdown strength improved obviously and reached 19.9 kV/mm at x=7.5. In virtue of low dielectric loss (tan δ<0.001 5), moderate dielectric constant (ε_r >1 500) and high breakdown strength (E_b >17.5 kV/mm), the CaZrO₃ doped (Ba_0.6Sr_0.4)_0.85Bi_0.1TiO₃ ceramic is a potential candidate material for high power electric applications.     

Photocatalytic performance of TiO<Subscript>2</Subscript> thin films connected with Cu micro-grid

Aiming at reducing the recombination of photo-induced carriers in semiconductor photocatalytic process, we prepared TiO₂ thin film with its surface modified by a connected Cu micro-grid via a microsphere lithography strategy, which showed higher photocatalytic activity than the pure TiO₂ film. The improvement of photocatalytic activity of Cu micro-grid to the TiO₂ film is due to the charge carrier separation and electron transfer by the conducting metal grid. The photocatalytic activity was improved as metal loading increased, which obtained the best performance at a certain loading amount, and then decreased at higher loading amount. This phenomenon was attributed to the metal’s bulk effect which could be explained by the relationship between the energetic positions and the metal cluster size. Supported by the National Natural Science Foundation of China (Grant Nos. 50672003, 50872005) and the National Basic Research Program of China (“973” Project) (Grant No. 2007CB613302) and the Fok Ying Tong Education Foundation (Grant No. 111050)     

Carbon nanotube coating on titanium substrate modified with TiO<Subscript>2</Subscript> nanotubes

A combination of carbon nanotubes (CNTs) and titanium (Ti) modified with TiO2 nanotubes (TiO2 NTs) was fulfilled with the aim of improving bioactivity of Ti implant.First,well-ordered TiO2 NTs were prepared by the electrochemical anodization of Ti in an ethylene glycol electrolyte containing 1 wt% NH4F and 10 wt% H2O at 20 V for 50 min,followed by annealing.Then,the carboxylated CNTs were coated onto the TiO2 NTs using electrophoretic deposition (EPD) technique.The growth of hydroxyapatite (HA) on the samples was investigated by soaking them in simulated body fluid (SBF).The result showed the CNTs-coated Ti with the modification of TiO2 NTs (CNTs-TiO2 NTs) was more efficient to induce HA formation than the CNTs-coated smooth Ti (CNTs-Ti).The vitro cell response was evaluated using osteoblast cells (MC3T3-E1).The good cell proliferation and strong cell adhesion could be obtained on the CNTs-TiO2 NTs.These results indicated that CNT coating on the Ti modified with TiO2 NTs could be potentially useful for the periodontal ligament combination on dental implants.     

Pool boiling on the superhydrophilic surface with TiO<Subscript>2</Subscript> nanotube arrays

Surface with TiO₂ nanotube arrays (TNTAs) is superhydrophilic and of great specific area. This paper investigates the pool boiling characteristics at the thermal interface with TNTAs. The results show that the TNTAs interface can enhance the pool boiling heat transfer compared to the pure Ti metal plate. The bubbles formed at the initial nucleation state are very small and released in higher frequency. The pool boiling heat transfer enhancement at the TNTAs interface may be attributed to the high density of nucleate site, high intrinsic heating area of nanotubes layer, superhydrophilicity and the vertically oriented nanotube structure. Supported by the National Natural Science Foundation of China (Grant No. 50846069)     

Hierarchical Co<Subscript>3</Subscript>O<Subscript>4</Subscript> microstructures decorated with Ag and Cu oxides: Study of photocatalytic and electrochemical properties

Three-dimensional hierarchical Co₃O₄ microstructures decorated with Ag and Cu oxides were prepared via displacement reaction and subsequent annealing treatment. Photocatalytic properties measurements revealed that the photocatalystic activities of CuO/Co₃O₄ composites (Co₃O₄ microstructures decorated with CuO) were enhanced while those of Ag₂O/Co₃O₄ composites (Co₃O₄ microstructures decorated with Ag₂O) were reduced, when compared with those of pure hierarchical Co₃O₄ microstructures toward the degradation of methyl orange. In addition, CuO/Co₃O₄ composites exhibited an excellent recyclability ability of photodegradation. The electrochemical properties test indicated that both of the composite oxide electrodes exhibited excellent pseudocapacitive performance with relatively high specific capacitance and good long-term cycling stability. With the increase of the loaded Ag₂O and CuO dosages deposited on the Co₃O₄ microstructures surface, the specific capacitance values of the composites were increased. Ag₂O/Co₃O₄ composite electrodes showed higher specific capacitance values and better cycling stability than CuO/Co₃O₄ composite ones.     

Photocatalytic degradation of rhodamine B dye with MWCNT/TiO<Subscript>2</Subscript>/C<Subscript>60</Subscript> composites by a hydrothermal method

Multi-walled carbon nanotube (MWCNT)/TiO2/C60 composite catalysts were prepared by hydrothermal method. TiO2 was deposited on the MWCNT surface. Their photocatalytic activities for degradation of Rhodamine B dye were studied. X-ray diffraction, field emission transmission electron microscopy, ultraviolet-visible light absorption spectrum and photoluminescence spectrum were carried out to characterize the composite catalysts. The results indicated that MWCNTs and C60 could greatly enhance the photocatalytic activity of TiO2.     

Hydrothermally Synthesizing Nanospheres of Pd Loaded TiO<Subscript>2</Subscript> for Photocatalytically Reducing CO<Subscript>2</Subscript> in Isopropanol to Isopropyl Formate

Photocatalytic reduction of CO₂ was carried out on villiform spherical catalysts of Pd-TiO₂ in isopropanol solution. The catalysts were synthesized by hydrothermal method, their structures, morphologies and optical absorption properties were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and UV-vis absorption spectroscopy (UV-vis). The photocatalytic activities with different loading amounts and morphologies were evaluated for determining the dominant effect and optimizing the catalyst preparation. Based on a villiform spherical TiO₂ with the largest specific surface area in our experiments, we prepared a set of catalysts with various loading amounts of palladium and tested them by bubbling CO₂ through the slurry of catalyst and isopropanol. The highest formation rate of isopropyl formate was 276.6 μmol/g·cat/h. Eventually we proposed the reaction mechanism.     

Fabrication and photocatalytic activity of Ag<Subscript>3</Subscript>PO<Subscript>4</Subscript>-TiO<Subscript>2</Subscript> heterostructural nanotube arrays

To extend the absorption capability of TiO₂ into visible light region and inhibit the recombination of photogenerated electrons and holes, we put forward an effective strategy of the coupling of TiO₂ with a suitable semiconductor that possesses a narrow band gap. Meanwhile, Ag₃PO₄-TiO₂ heterostructural nanotube arrays were prepared by the two-step anodic oxidation to obtain the TiO₂ nanotube arrays and then by a deposition-precipitation method to load Ag₃PO₄. The samples were characterized by field emission scanning electron microscopy (FESEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), and UV-vis diffuse reflectance spectroscopy (UV-vis DRS). The experimental results showed that Ag₃PO₄ nanoparticles were uniformly dispersed on the highly ordered TiO₂ nanotube arrays, which increased the visible-light absorption of TiO₂ photocatalyst. The photocurrent density and photocatalytic degradation of methyl orange indicated that the performance of Ag₃PO₄-TiO₂ heterostructural nanotube arrays was better than that of the TiO₂ nanotube arrays, which could be attributed to the effective electron-hole separation and the improved utilization of visible light.