Jarnuzi Gunlazuardi

Water disinfection using an immobilised titanium dioxide film in a photochemical reactor with electric field enhancement

We have produced an adherent defect TiO2 film reactor in which the performance is greatly improved by the application of a small positive bias (electric field enhancement) to boost hydroxyl radical production. In the reactor the light, electric field and photocatalyst combined to disinfect water containing Clostridium perfringens spores and Escherichia coli. Singly, neither light, the electric field or the combination of light and fixed film could significantly reduce the numbers of indicator bacteria. We believe that water disinfection using an immobilised titanium dioxide film photochemical reactor with electric field enhancement could provide an effective and energy efficient source of hydroxyl radicals for water disinfection.

Effect of catalyst type on the kinetics of the photoelectrochemical disinfection of water inoculated with E. coli

The rates of the photoelectrochemical disinfection of Escherichia coli at TiO2 electrodes were measured as a function of concentration and applied potential. Two different TiO2 photoelectrodes were used: a thermally treated titanium plate and a porous film prepared by a sol–gel hydrolysis technique. The kinetics of the disinfection process were found to depend upon the nature of the electrode material. For the thermal film they were first order, and half order for the sol–gel film. It was also found that the catalytic activity per unit surface area of catalyst is many orders of magnitude greater than that observed using TiO2 slurries; this was attributed to the reduced rate of electron-hole recombination afforded by the application of a small potential bias (∼1 V vs Ag/AgCl), and hence the exploitation of the electric field enhancement (EFE) effect.

Preparation and Characterization of Magnetite-Silica Nano-Composite as Adsorbents for Removal of Methylene Blue Dyes from Environmental Water Samples

Magnetite-silica nanocomposites (Fe3O4/SiO2) have been synthesized and characterized and were used as an effective sorbent material for dyes removal from environmental water samples. They were prepared by a simple procedure via a co precipitation of iron (II) and iron (III) ion mixture in ammonium hydroxide and then was impregnated by a sodium silicate. The prepared samples were characterized using Zeta potential, XRD, VSM, TEM, EDS, and porosity analysis. The result of characterization showed that Fe3O4 nanoparticles have been coated by silica. The composite have been superparamagnetic behaviour at room temperature and contain both meso-and microporosity system. Mesoporosity contributes dominantly to the pore volume. Adsorption performance of magnetic-silica nanoparticles were examined its ability to adsorp methylene blue dye in aqueous solution. The 20 mg/L of initial concentration of methelene blue, 1 gr/L adsorbent in solution and under shakker for 5 hour, the remain of methylene blue in solution was 13,3% for Fe3O4/SiO2 (3:1), 30,2% for Fe3O4/SiO2 (2:1) and 24,2 % for Fe3O4/SiO2 (1:1). The composite was effective to adsorb dyes in water and can be easily recovered from treated water with helping of magnetic bar.

Preparation and Characterization of Fe3O4/TiO2 Composites by Heteroagglomeration

Fe3O4/TiO2 composites were prepared by heteroagglomeration. The composites of different Fe3O4 to TiO2 weight ratio were prepared by mixing of prepared Fe3O4 with TiO2 in aqueous slurry, under ultrasonic treatment. All prepared samples were characterized by XRD, VSM, SEM/EDS, raman spectroscopy and BET. The prepared composites contained TiO2 (anatase and rutile) and Fe3O4 crystal phases. The magnetization hysteresis loop for Fe3O4/TiO2 nanocomposites indicated that the hybrid catalyst showed superparamagnetic characteristics at room temperature. Photocatalytic performance of the prepared composites was examined by its ability to degrade methylene blue dye in aqueous solution. The photocatalytic activity of Fe3O4/TiO2 composites was lower than that of pure TiO2 sample because of the presence of non-active photocatalytic in composite (iron oxide). Under UV irradiation, the photocatalytic activity of Fe3O4/TiO2 (1:1) composite was relatively similar to Fe3O4/TiO2 (1:2), however, under sunlight irradiation, the photocatalytic activity of Fe3O4/TiO2 (1:2) composite was relatively increase. The Fe3O4/TiO2 composite can be easily recovered from treated water in slurry-type reactor by the application of an external magnetic field.

Photo-electro-catalytic performance of highly ordered nitrogen doped TiO2 nanotubes array photoanode

Highly ordered nitrogen doped TiO2 nanotube arrays (N-TNTAs) were synthesized via a one step anodization method at 40 V for 1 hour, in the electrolyte containing ammonium fluoride (NH4F), water and triethylamine solution, followed calcination under N2 atmosphere at 450oC for 3 h. The obtained samples were characterized by means of FE-SEM image showed that the N-TNTs are in a highly ordered array, having inner diameters, wall thickness, tube length of 65 nm, 30 nm and 900 nm, respectively. The X-ray diffraction (XRD) patterns of N-TNTAs and undoped TiO2 nanotubes arrays (TNTAs) are identical consists of anatase phase, which suggests that the doping of N does not affect the crystalline structure. X-ray photoelectron spectroscopy (XPS), revealed that N atom was incorporated into the lattice of a TiO2 nanotube array film. The infrared spectra, showed a new peak at 1240 cm-1 may indicate the incorporation of N into the lattice of TiO2 through substituting O atoms, in the form of ~N-Ti-O~. A red shift of the absorption edge toward the visible region of N-TNTAs are observed by diffuse reflectance spectroscopy (DRS), which is corresponding to a band gap of 2.8 eV. The photo-electro-catalytic (PEC) degradation efficiency toward methylene blue solution under visible light illumination of the N-TNTAs electrode was 89%, in which the rate constant of N-TNTAs electrode was 8 times better compared to that the undoped TNTAs photo-electrode.

PHOTOCURRENT ENHANCEMENT OF CdS QUANTUM DOT SENSITIZED TiO2 ELECTRODE IN THE PRESENCE OF GOLD NANO PARTICLES

PHOTOCURRENT ENHANCEMENT OF CdS QUANTUM DOT SENSITIZED TiO 2 ELECTRODE IN THE PRESENCE OF GOLD NANO PARTICLES . Photo current enhancement of CdS Quantum Dot (CdS-QD) sensitized TiO 2 electrode in the presence of gold nano particles had been investigated. CdS quantum dots were prepared by successive ionic layer adsorption and reaction (SILAR) method, in which solution containing Cd(CH 3 COO) 2 and Na 2 S were used as a precursor. Where as, gold nano particles was synthesized using solution containing HAuCl 4 as a precursor, NaBH 4 as a reducing agent and polyvinyl pyrrolydone (PVP) as a stabilizer. The film of CdS quantum dots and Au nano particles were characterized by UV-Vis spectrophotometer, Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), and electro chemical working station. Photo electrochemical study revealed that CdS-sensitized TiO 2 electrode with gold nanoparticles have been able to increase photocurrent of 54 A/cm 2 to 68 A/cm 2 , so the photocurrent enhancement of approximately 25% was observed. This observation indicates that the gold nanoparticles is potentially applicable to enhance photocurrent in a CdS-QD sensitized TiO 2 electrode, which may lead to the development of more efficient solar cell.

Photocatalytic Decomposition of Glycerol Solution on TiO2 Nanotube Arrays (TNTA) Doped with C and N to Produce Hydrogen

Carbon and Nitrogen-doped TNTA were synthesized by in-situ anodic oxidation of Ti using glycerol containing NH4F followed by annealing with 20% H2/Argon at 500 °C. Variation water content in the electrolyte solution (25 and 37.5 v%) and time of anodic oxidation (1, 2, 4 and 6 h) that influence the morphology of TNTA and H2 produced was examined. At water content 37.5 v% in the electrolyte solution, FESEM results indicated that the disorder with not vertically oriented of the tube were observed. For water content 25 v%, TNTA with average inner diameters of 81 to 105 nm, wall thicknesses from 15 to 27 nm and lengths from 882 to 1705 nm were synthesized for 1-6 h anodization. Morphology of TNTA such as well developed, vertically oriented, ordered and long could influence photon absorption and, therefore, influence the accumulative H2 production. The result indicated that the average inner diameter of the tubes increase as anodic oxidation time increased up to 6 h, on the other hand, the tube length reached the maximum at 4 h anodic oxidation. TNTA that anodized for 2 h, water content in the electrolyte solution 25 v% with average tube length 1570 nm showed the highest accumulative H2 production (47 mmol/m2photocatalyst).

Electrodeposition of gold nanoparticles on mesoporous TiO2 photoelectrode to enhance visible region photocurrent

Electrodeposition of gold nanoparticles (Au NPs) on the mesoporous TiO2 photoelectrode to enchance visible region photocurrent have been investigated. Mesoporous TiO2 was prepared by a sol gel method and immobilized to the fluorine doped tin oxide (FTO) substrate by dip coating technique. Gold nanoparticles were electrodeposited on the TiO2 surface and the result FTO/TiO2/Au was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), UV-Vis diffuse reflectance spectroscopy (DRS), and X-ray diffraction (XRD). The generated photocurrent was evaluated with an electrochemical workstation (e-DAQ/e-recorder 401) using 60 W wolfram lamp as visible light source. The photoelectrochemical evaluation indicated that the presence of gold nanoparticles on TiO2 photoelectrode shall enhance the photocurrent up to 50%.

Copper-Zinc-Titania Nanocomposite as Catalyst for CO2 Photo-Reduction: A Surface Deactivation Study

In this paper, a surface deactivation study of Cu1.0-Zn0.5-Ti98.5 oxide nanocomposite (CZT-ONC) as catalyst for photo-reduction of CO2 in aqueous solution is reported. The photo-reduction experiments were conducted through five experimental cycles. The results demonstrated that the activity of the CZT-ONC decreased by increasing the number of testing cycle. The causes for declining the activity of the CZT-ONC catalyst was studied by investigating the surface condition of the catalyst before and after used by mean X-ray photoelectron spectroscopy (XPS) and field emission-scanning electron spectroscopy (FE-SEM) techniques and the results are discussed. It was found that the surface conditions (chemical state of the elements and morphology) of the CZT-ONC catalyst have been critically altered. Change in surface condition pointed that the deactivation process on the surface of the CZT-ONC was occurred and it could be considered to be the reasons for declining of the activity.

Formation of Tio2 Thin Film for Dye‐Sensitized Solar Cell Application Using Electrophoresis Deposition

One of important processes on the fabrication of dye‐sensitized solar cell (DSSC) is formation of TiO2 thin film. Thickness of TiO2 thin film is needed to be controlled in order to obtain optimum TiO2 thickness. Electrophoresis deposition is simple method for thin film deposition which enable us to control the thickness of thin film. In this work, the formation of TiO2 thin film on indium‐doped tin oxide (ITO) glass using electrophoresis deposition is numerically and experimentally studied. We have succeeded to control the thickness of TiO2 thin film by changing of electrophoresis applied voltage and deposition time. In the experiment, TiO2 particles were suspended into isopropyl alcohol solution. Mg(NO3)2 was added to the solution in order to obtain the stable solution for electrophoresis. We found numerically that the Mg(NO3)2 in the range from 10−6 M to 10−4 M, is appropriate condition for the electrophoresis deposition. Using this method, we have fabricated DSSC device and study the effect of TiO2 thi...