Qingnan Zhao

Effect of surface structure on photocatalytic activity of TiO2 thin films prepared by sol-gel method

TiO2 thin films with different surface structures are prepared from alkoxide solutions containing polyethylene glycol (PEG) via the sol-gel method. The effects of PEG addition to the precursor solution on the surface structures and photocatalytic activity of the resultant thin films are studied. The larger the amount of PEG added to the precursor solution, the larger the size and number of pores produced in the resultant films when PEG added to the gel films decomposed completely during heat-treatment. The adsorbed hydroxyl content of such porous thin films is found to increase with increasing amount of PEG. However, the transmittance of the films decreases due to the scattering of light by pores of larger size and bigger number in the films. Photocatalytic degradation experiments show that methyl orange is efficiently decolorized in the presence of the TiO2 thin films by exposing its aqueous solution to ultraviolet light and the suitable surface structures remarkably enhance the photocatalytic activity of TiO2 films.

Photocatalytic activity of nanometer TiO2 thin films prepared by the sol-gel method

Abstract Transparent TiO2 nanometer thin films with high photocatalytic activity were prepared on soda-lime glass substrates via the sol–gel method using the TiO2 sol solution. The valency state of Ti element and the chemical compositions in TiO2 thin films were analyzed with X-ray photoelectron spectroscopy (XPS). Experimental results showed that besides Ti, O and C elements there is a small amount of Na and Ca elements diffused from the glass substrates and besides Ti(IV) there is a certain amount of Ti(III) and Ti(II) in TiO2 thin film. Heating temperature of 500°C may be adopted to convert TiO2 gel films into TiO2 (anatase) crystalline films and also the TiO2 (anatase) crystalline films show the highest photocatalytic activity. It was also found that the heat treatment for a suitable time at 500°C improves remarkably the photocatalytic activity of the TiO2 thin film, although for too long a time, rather deteriorates it. These results are explained on the basis of the changes in the surface structure and Ti3+ concentration with the heat treatment time.

Preparation and characterization of super-hydrophilic porous TiO2 coating films

In this study, the super-hydrophilic TiO2 coating films are prepared from alkoxide solutions containing polyethylene glycol (PEG) by the sol‐gel method on soda lime glass. The effects of PEG addition to the precursor solution on the super-hydrophilic property and microstructure of the resultant coating films are studied. The larger the amount and molecular weight of PEG, the larger are the size and numbers of pores produced in the resultant coating films on the decomposition of PEG during heat treatment. The adsorbed hydroxyl content of such porous coating films is found to increase due to the larger size and number of pores in the coating films. However, the transmittance of the coating film decreases due to the scattering by the larger size and number of pores. The contact angle for water of porous TiO2 coating film decreases with the increase of the adsorbed hydroxyl content, capillary force and roughness of the resultant coating films.

Highly Efficient Visible-Light-Induced Photocatalytic Activity of Nanostructured AgI/TiO2 Photocatalyst

Nanostructured AgI/TiO(2) photocatalyst was synthesized by a feasible approach with AgNO(3), LiI, and Ti(OBu)(4) and characterized by X-ray diffraction, transmission electron microscopy, angle-dependent X-ray photoelectron spectroscopy, diffusive reflectance UV-vis spectroscopy, Raman spectroscopy, photoluminescence, and the Brunauer-Emmett-Teller technique. The results of characterization reveal that the nanostructured AgI/TiO(2) has a novel core/shell/shell nanostructure of AgI/Ag-I(2)/TiO(2). Compared with TiO(2) (P25) supported AgI, the formation of the nanostructure results in substantial shifting of the absorption edge of AgI to red, enhancement of the absorption intensity, and the appearance of a strong tail absorption above 490 nm, which is assigned to the absorption of I(2) and Ag. Photocatalytic tests show that the nanostructured AgI/TiO(2) photocatalyst exhibited very high visible-light-induced photocatalytic activity for the photodegradation of crystal violet and 4-chlorophenol, which is 4 and 6 times higher than that of P25 titania supported AgI, respectively. The highly efficient visible-light-induced photocatalytic activity of the nanostructured AgI/TiO(2) is attributed to its strong absorption in the visible region and low recombination rate of the electron-hole pair due to the synergetic effect among the components of AgI, Ag, I(20, and TiO(2) in the nanostructured AgI/TiO(2).

The grain size and surface hydroxyl content of super-hydrophilic TiO2/SiO2 composite nanometer thin films

The grain size and surface hydroxyl content of super-hydrophilic TiO2/SiO2 composite nanometer thin films JIAGUO YU∗ State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, 430070, People’s Republic of China; Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, People’s Republic of China E-mail: yujiaguo@public.wh.hb.cn

XPS Study of N-doped TiOx Thin Films Prepared By DC Reactive Magnetron Sputtering

The N-doped TiOx films, coated on glass substrates, were prepared by DC reactive magnetron sputtering using Ti metal target in a mixture of Ar, O2 and N2. The dependence of the films composition on ratio of N2 partial pressure to total pressure was investigated using X-ray photoelectron spectroscopy (XPS). The XPS results show that N1s line is composed of three peaks at the binding energies of 396.0±0.2eV, 399.9±0.2eV and 402.0±0.4eV, respectively; for an increasing ratio two regimes are observed. For the ratio between 0.01 and 0.05, with the increase of the ratio, the N1s concentration at 396.0±0.2eV increases from 0.002 to 0.007 and the O1s concentration at 531.9±0.2eV increases from 10.8 to 62.7; for the ratio between 0.05 and 0.11, with the increase of the ratio, the N1s concentration at 396.0±0.2eV decreases from 0.007 to 0.003 and the O1s concentration at 531.9±0.2eV decreases from 62.7 to 18.7. The O1s at a binding energy 531.9±0.2eV corresponds to hydroxyl groups. With the increase of the ratio, the atomic ratio O/Ti varies from 1.98 to 1.93, and the chemical state of the Ti is kept at Ti. The more N1s at 396.0±0.2eV, the more O1s at 531.9±0.2eV, that is, more hydroxyl groups (OH) on the surface of the N-doped TiO2 film.

The Structure and Photocatalytic Activity of CeO2 Doped TiO2 Films Deposited onto Glass by Magnetron Sputtering

In this paper, the CeO 2 doped TiO2 films, coated on glass substrates, were prepared by R.F and D.C sputtering for CeO 2 target and pure Ti target, respectively. The structure of the ilms was analyzed using XRD, XPS and SEM, the photocatalytic properti es of the films were characterized by degradation of methyl orange solution. The resul ts showed that the films were amorphous before annealed or annealed at lower than 300 C; after annealing at 300 C and 330 C, the films were TiO2-anatate, and the SEM images of the films revealed nanometer size crystal and pores; The films showed a substantially enhanced activity for t he degradation of the methyl orange as compared to the pure TiO 2 film. The highly photocatalytic activity of the CeO 2/TiO2 films was attributed to the TiO2-anatate, the structure of the films was nanometer size cryst al and pores, and the potential of Ce /Ce couple (E=~1.5eV versus NHE) is more positive than that of the H /H, which makes the electrons of the conduction band (TiO 2) be transferred more easily to Ce /Ce than to H/H. The results were discussed in detail.