Photocatalytic Performance of TiO2 as a Catalyst
- 1. Photocatalytic Performance of Dye Doped Graphene Supported Titania Under Sunlight Presented by: Muhammad Aamar Azam M.Phil Physics - UAF
- 2. Problem • Use of TiO2 as catalyst is solution of energy problem as it converts solar energy into chemical energy. • Due to large bang gap (3.2 eV) of TiO2 works in UV range spectrum which is only 5 % of sunlight. Objective • The aim of this work is to improve its photocatalytic performance by doping a suitable dye in it so that it works in visible range spectrum.
- 3. Titanium Dioxide (TiO2) as a Catalyst TiO2 is a white powder solid It is most studied photocatalyst in field of photocatalysis Atmospheric oxygen is used for reaction It has strong oxidizing power It is cheap, non-toxic, abundant Chemically stable High resistance to photo-corrosion Found in three phases i) Anatase ii) Rutile iii) Brookite
- 4. Why anatase
- 5. Photocatalysis Photocatalysis is a reaction which uses light to activate a substance (catalyst) which modifies the rate of a chemical reaction without being involved itself. Photosynthesis Photosynthesis is a process by which plants prepare their own food (oxygen and glucose) by using Chlorophyll (natural photocatalyst) in the presence of carbon dioxide and water under sunlight.
- 6. holes and electrons breakdown the organic matter to carbon dioxide and water. chlorophyll turn water and carbon dioxide into oxygen and glucose Opposite
- 7. Photocatalyst o It is a substance that takes part in a chemical reaction and can alter the rate of reaction, without being consumed at the end of the reaction. Reaction Kinetics o A catalytic reaction is compared to a reaction which is not using catalyst. o top curve=uncatalyzed reaction o lower curve=catalyzed reaction o Activation energy=energy difference between energy of reactant and top of energy curve Addition of a catalyst reduces the activation energy.
- 8. Principle of photocatalysis • TiO2 absorbs light • Electron-Hole pairs are produced • Electrons reduces nearby oxygen • Highly oxidizing Holes oxidizes nearby water • Both anion and radical break organic compounds
- 9. Improvement in Photocatalytic Activity Photocatalytic activity of TiO2 can be improved by following i) By increasing the electron-hole recombination time ii) By decreasing energy band gap of catalyst iii) By increasing light absorption level of catalyst Surafce Area Carrier Transport Band Gap Controlling Factors
- 10. In 2001, Japanese chemist Asahi et al., Nitrogen doped titanium dioxide showed effective visible light activity. In 2003, Teruhisa et al., showed that S-doped TiO2 perform better under visible light In 2003, Hiroshi et al., Carbon dopedTiO2 shows better activity under visible light In 2005, Kim et al., showed Platinum-ion-dopedTiO2 showed good performance in visible light The reason for this activity was also explained by other scientist by describing that doping narrowed the energy band gap of titania
- 12. Materials and Methods Electric Furnace Dry Oven It is used to calcinate samples at high temperature It is used for drying and heating purpose.
- 13. Autoclave UV Visible Spectrometer It is used for doping purpose It is used for UV analysis
- 14. Other materials and apparatuses Magnetic Hot Plate Stirrer pH paper Pipet China dishes Titanium tetraisopropoxide Distilled water Sample bottles Indigo dye Flasks Aluminum foil Permanent magnet Burette Ethanol Hydrochloric Acid Reduced graphene oxide
- 15. Sol-gel Technique Sol-gel technology is widely used and it is an effective process to produce TiO2 nanoparticles. It involves the conversion of precursor solution into nanostructured solid. Advantages: Low processing cost Low processing temp. High purity Simple, economic, effective Desired nanoparticle Fine homogeneous powder
- 16. It states that x-rays reflected from different parallel planes of a crystal interfere constructively when path difference is integral multiple of wavelength. nλ=2d sin θ This gives maximum intensity of reflected beam. Bragg’s law is the fundamental principle of X-ray diffraction analysis (XRD) This law relates the wavelength of electromagnetic radiation to the diffraction angle and the lattice spacing
- 17. UV-Vis Spectroscopy Principle Beer-Lambert law The Beer-Lambert law states that the quantity of light absorbed by a substance dissolved in a fully transmitting solvent is directly proportional to the concentration of the substance and the path length of the light through the solution. A = a(λ) . b . c A is the measured absorbance, a(λ) is a wavelength-dependent absorptivity coefficient A = a(A = a( ) * b * c
- 18. Sample Preparation 80 ml of distilled water and 11 ml of Hydrochloric acid (HCL) were taken into a beaker and put into the burette. After that, 20 ml of Titanium tetraisopropoxide was dissolved into 220ml Ethanol solution. After that Hydrochloric acid (HCL) solution was allowed to add into the milky solution then dried and calcinated. Sol-gel Method