Jia Wei Bai

Photocatalytic Activity of TiO2/Ti Film Prepared by Sol-Gel Method on Methyl Orange Degradation

TiO2 film was deposited on titanium substrate by a sol-gel dip-coating process. Photocatalytic activities of the films prepared with and without template were compared. The TiO2 film deposited on Ti substrate obviously could not adsorb methyl orange on its surface and the titanium substrate had very weak activity under UV light irradiation. The TiO2 films prepared without the addition of PEG1000 were calcinated at 450 oC, 500 oC, 550 oC, and 600 oC and the film calcinated at 500 oC showed the optimum photocatalytic degradation activity. The addition of PEG1000 could promote degradation of methyl orange that can be attributed to the possible pore forming in the TiO2 film.

Photoelectrocatalytic Degradation of Methyl Orange on Porous TiO2 Film Electrode in NaCl Solution

Porous TiO2 films and smooth TiO2 films were fabricated by sol-gel dip-coating technique using titanium plate as support substrate. Photoelectrocatalytic (PEC) degradation of methyl orange was investigated in aqueous NaCl solution using the TiO2 films. PEC degradation efficiencies showed strong dependence on the concentrations of aqueous NaCl solutions and applied potentials. Photoelectrocatalytic activity of the porous TiO2 film was higher than that of the smooth TiO2 film at lower applied potential. 95.2% decolorization of the dye could be achieved in 50 minutes at applied potential of 0.6 V in 0.05 M NaCl solution on porous TiO2 films, while the efficiency was only 79.9% on smooth TiO2 films. Electrodegradation (ED) of these two film electrodes almost had no effect on methyl orange. Photocatalytic oxidation (PCO) degradation was 36.4% for the porous TiO2 thin film after 80 min, and 32.6% for the smooth TiO2 thin film during the same condition.

PEG and ODA as Composite Templates to Prepare Porous TiO2 Films by Sol-Gel Method

Porous TiO2 films were prepared through dip-coating on glass substrates using composite templates of PEG and ODA. Photocatalytic activity of the photocatalyst was evaluated by measuring removal rate of aqueous methyl orange under UV light irradiation. The addition of composite templates had obvious influence on surface morphology of the films. Layered and porous structures formed in the surface due to the function of templates. When the amount of PEG in the composite template increased from 0.1 g to 1.9 g, adsorption edge of the films moved to longer wavelength region. When the amount of PEG increased to 1.0 g, there were sharp decrease of specific surface area and cumulative pore volume. The improving photocatalytic activity as a result of addition of PEG can be noticed.

Characterization of TiO2 Film Prepared by Sol-Gel Method Using Ti(OC4H9)4

TiO2 film was dip-coated on glass substrate by a sol-gel process. Ti(OC4H9)4 was used as the titanium source. Surface morphology, crystallite phase, UV-Vis transmittance spectrum and pore size distribution of TiO2 powder prepared under the same conditions of the film were investigated. Surface of TiO2 film is fairly smooth with very slight roughness. No obvious hole or pore is found on the surface of the film. The strongest diffraction peak situated at 2θ=25.3o is the characteristic of anatase TiO2. The absorption edge of the TiO2 film is around 350 nm, while the transmittance fluctuates between 50% and 90%. The average pore size of the TiO2 particles calculated by BJH method is 23 nm. The total pore volume and specific surface area are 0.16 ml/g and 27 m2/g, respectively.

Photoelectrochemical Degradation of Cyanuric Acid in TiO2 Suspension

Photoelectrochemical degradation of cyanuric acid occurred when the applied potential exceeded 2 V by using Ti electrodes and TiO2 suspension in 0.3 M NaCl solution. The removal increased drastically when the applied potential was more than 5 V. The addition of HCO3- ion could accelerate photoelectrochemical degradation of cyanuric acid. An optimum removal of 85% was achieved when HCO3- ion concentration increased to 0.05 M. Further increase of HCO3- ion led to the decrease of removal, due to consumption of hydroxyl radicals and other oxidizing species by excessive bicarbonate. Photocatalytic oxidation had no capacity on degrading cyanuric acid whether in NaHCO3 aqueous solution or in the solution containing both Cl- and HCO3- ions.

Methyl Orange Photoelectrocatalytic Degradation Using Porous TiO2 Film Electrode in NaH2PO4 Solution

Porous TiO2 film was prepared by a sol-gel method using PEG1000 as pore forming template. The porous film and normal film were used as electrodes in a photoelectrocatalytic reactor. The functions of applied potential and concentration of NaH2PO4 to the photoelectrocatalytic degradation process of methyl orange were investigated. The results show that methyl orange cannot be degraded solely by the applied potential. Under the applied potential of 2 V, 49.9% of the initial dye can be removed on the normal TiO2 film electrode, which is much better than the 31.1% removal rate on the porous TiO2 film electrode. The normal TiO2 film electrode has better performance than the porous TiO2 film in the whole NaH2PO4 concentration range. After 80 min of reaction, degradation rate is 93.7% on the normal TiO2 film electrode. After 100 min of reaction, degradation rate is 89.7% on the porous TiO2 film electrode.

Properties of Porous TiO2 Films with Different Layers Coated on Glass Substrate

Porous TiOB2B films were dip-coated on glass substrate by sol-gel process. Ti(OCB4BHB9B)B4B was used as the titanium source and PEG1000 was used as a template. Surface morphology and UV-Vis transmittance spectra were investigated as the factor of the number of TiOB2B layers. The films containing 1 to 3 TiOB2B layers seem to be quite smooth with very slight roughness. While on the surface of the films containing 4 to 6 TiOB2B layers, particles aggregated on the surface accompanied with the formation of small holes. The adsorption edges of the coated films moved to higher wavelength region with increasing film layers. In the wavelength range from 350 to 450 nm, transmittances of the films declined first and then went up when the films got thicker.

Characterization of Porous TiO2 Films Prepared Using PEG of Different Molecular Weight

Porous TiO2 films were prepared through dip-coating on glass substrates using different molecular weight of PEG. Surface roughness increased with increasing PEG molecular weight. The film prepared with PEG400 was fairly smooth with slight roughness. The films prepared with high molecular PEG became rougher and there were some larger particles on the films. When the PEG molecular weight got higher, adsorption edge of the films tended to move toward shorter wavelength region. In the wavelength range between 350 and 450 nm, larger PEG molecules made higher film transmittance. The particles prepared using higher or lower molecular weight of PEG had less surface area than using PEG1000. The average pore sizes were 14 nm, 15 nm, 28 nm, and 52 nm, and the total pore volume were 0.12 ml/g, 0.13 ml/g, 0.08 ml/g, and 0.09 ml/g for the TiO2 powders prepared using PEG400 to PEG 6000.

A Combined System of TiO2 Suspension and Platinum Electrodes Used for Photoelectrochemical Degradation of a Dye in NaCl Solution

Photoelectrochemical (PEC) degradation of Procion Red MX-5B was investigated in aqueous NaCl solutions. PEC degradation efficiencies showed strong dependence on the concentrations of aqueous NaCl solutions and applied potentials. 95% decolorization of the dye could be achieved in 10 minutes at applied potential of 8 V in 0.3 M NaCl solution, while the efficiency was only 35% by photocatalytic oxidation. Electrodegradation can be as powerful as PEC degradation upon dye decolorization when the potential exceeds 5 volts. However, it can not mineralize dye degradation intermediates by itself alone. PEC degradation performed very high TOC removal capacity and nearly 80% of total organic carbon was removed in the first hour of reaction, compared with 50% removal in PCO process during the same period.

Photoelectrochemical Degradation of Procion Red MX-5B in TiO2 Suspension Using Na2SO4 as Electrolyte

Photoelectrochemical (PEC) degradation of Procion Red MX-5B was investigated in aqueous Na2SO4 solution. Higher electrolyte concentration resulted in higher current between the electrodes due to increased conductivities of the solutions. UV irradiation could obviously raise the current, and the differences became larger in accordance with the increase of the applied potentials. The pH declined in the first 30 minutes and became constant for the prolonged reaction time during both PEC degradation and photocatalytic oxidation. The applied potential could only slightly improve dye decolorization. Although a potential of 8 V was applied to 0.3 mol/l Na2SO4 solution, TOC removal efficiency of PEC degradation was almost as the same as that of photocatalytic oxidation.