Sensitization of sol-gel derived titania-silica photocatalytic thin films with ascorbic acid

Yılmaz, Emre
The photocatalytic activity of semiconductor metal oxides can be improved by the addition of sensitizer which enhances the band gap by considerable red shift of the absorption edge of semiconductor. In the present study, the effect of ascorbic acid as sensitizer on the photocatalytic activity of titania-silica binary mixtures was studied. The SiO2-TiO2 mixtures having 50wt%Ti:Si composition were prepared with sol-gel method. The surface area and porosity of the samples were modified by using various amounts of polyethylene glycol (PEG) as template. The thin films of the samples were obtained by dip coating of glass plates to colloidal solutions. The samples were characterized by methylene blue adsorption method and UV-Vis spectrophotometry. The photocatalytic activities of the samples were measured with methylene blue degradation, methyl orange degradation and direct water splitting in the presence and absence of ascorbic acid. Increase in the surface area and reaction rate with increasing PEG addition until a threshold value was observed. Highest methylene blue degradation activity was observed for 27g PEG added sol-gel derived film and surface area of this film is measured as 44m2/m2. Ascorbic acid presence shows a significant increase in the photocatalytic degradation activity of methyl orange. The sensitization effect of ascorbic acid was also compared with the effect of EDTA. It was found that the effect of ascorbic acid on the methyl orange degradation rate is significantly higher than the effect of EDTA. However, the effect of EDTA is more pronounced in water splitting reaction.


Catalytic partial oxidation of propylene on metal surfaces by means of quantum chemical methods
Kızılkaya, Ali Can; Önal, Işık; Department of Chemical Engineering (2010)
Direct, gas phase propylene epoxidation reactions are carried out on model slabs representing Ru-Cu(111) bimetallic and Cu(111) metallic catalyst surfaces with periodic Density Functional Theory (DFT) calculations. Ru-Cu(111) surface is modelled as a Cu(111) monolayer totally covering the surface of Ru(0001) surface underneath. The catalytic activity is evaluated following the generally accepted oxametallacycle mechanism. It is shown that the Ru-Cu(111) surface has a lower energy barrier (0.48 eV) for the s...
Dynamic analysis of changes in diffusion and sorption parameters in the reaction of SO2with activated soda ash
Doǧu, Gülsen; Keskin, Alne; Doǧu, Timur (Wiley, 1988-8)
Variations in pore structure cause significant changes in diffusion resistance and adsorption characteristics during the reaction of SO2 with activated soda. Breakthrough and moment analysis of the SO2‐activated soda ash reaction showed that the effective diffusion coefficient of SO2 in the solid product (mostly Na2SO3) was about three times smaller than its value in the original activated soda. About 30% of the diffusion flux of SO2 in the solid product was found to be due to surface diffusion. The adsorpt...
Acidity characterization and adsorption characteristics of cobalt and lead doped SBA15 mesoporous materials
Güner, Özge; Üner, Deniz; Department of Chemical Engineering (2007)
In this study, the surface acidity of Co and/or Pb doped SBA15 mesoporous catalysts were investigated by both diffuse reflectance fourier transform (DRIFT) infrared spectroscopy and transmission mode fourier transform infrared spectroscopy. Pyridine was used to identify the Brønsted and Lewis acid sites of the surface, at room temperature. From the DRIFT spectrum typical stretching vibrations of isolated terminal silanol (Si-OH) groups were observed for all the catalysts. These silanol group bands dissappea...
Chemical vapor deposition of boron carbide
Karaman, Mustafa; Özbelge, Önder; Department of Chemical Engineering (2007)
Boron carbide was produced on tungsten substrate in a dual impinging-jet CVD reactor from a gas mixture of BCl3, CH4, and H2. The experimental setup was designed to minimise the effect of mass transfer on reaction kinetics, which, together with the on-line analysis of the reactor effluent by FTIR, allowed a detailed kinetic investigation possible. The phase and morphology studies of the products were made by XPS, XRD,micro hardness and SEM methods. XPS analysis showed the existence of chemical states attrib...
Applicability of the power model to mixed slurries with non-spherical particles and networking effect
Kutukcu, Basak; Ayrancı Tansık, İnci (Elsevier BV, 2018-10-01)
Industrial applications of solids suspension generally consist of mixed slurries that contain many solid phases with irregularly shaped particles at high concentrations. Since solid-liquid mixing is a power intensive operation it is critical to predict the just suspended speed, N-j(s), accurately. There is only one model available for mixed slurry N-js predictions: the power model. This model was developed for spherical particles. In this study, suspension behaviour of mixed slurries with non-spherical part...
Citation Formats
E. Yılmaz, “Sensitization of sol-gel derived titania-silica photocatalytic thin films with ascorbic acid,” M.S. - Master of Science, Middle East Technical University, 2012.