Effect of metal dopant on photocatalytic performance of TiO2 nano particles
3 likes1,378 views
The document discusses the impact of metal doping on the photocatalytic performance of TiO2 nanoparticles, highlighting their properties, mechanisms, and applications in environmental remediation. Metal doping enhances the optical absorption and reduces the band gap energy, resulting in improved photocatalytic efficiency, particularly under visible light. Key factors influencing the photocatalytic activity include the concentration and type of metal dopant, as well as the characteristics of the TiO2 nanoparticles.
Effect of metal dopant on photocatalytic performance of TiO2 nano particles
- 1. 1 Effect of metal dopant on photocatalytic performance of TiO2 nano particles Presented by R.Gandhimathi
- 2. 2 ➢ Over view on nanoparticles ➢ Introduction to metal doped TiO2 nanoparticles ➢ Optical absorption and band gap modification upon doping ➢ Photocatalytic Mechanism ➢ Photocatalytic performance of TiO2 ➢ Conclusion Outline
- 3. Nanotechnology deals with the physiochemical, optical, electrical, and mechanical properties of materials whose size and shape are engineered at the nanoscale 1nm-one thousandth of a micron (10–9m) (or) a billionth of a meter OVER VIEW ON NANOPARTICLES Nano Particles ➢Include wide class of materials which are less than 100 nm in size and have at least one dimension ➢e.g. Atomic and molecular building blocks of matter i.e. bulk crystals with lattice spacing in nanometers ➢Nanoparticles can exist in either amorphous or crystalline form. ➢Different kinds of nanoparticles are metal, ceramic, semiconductor, polymeric lipid and carbon based particles Metal Liposomes Carbon nano tubes polymers Semiconductor 3 Different types of nanomaterials Dimension of nanomaterials
- 4. ➢ Metal oxide anatase phase semiconductor ➢ Photo-induced catalytic ability under ultraviolet irradiation ➢ Appropriate material for treatment of both water and air pollution, water splitting reactions, antibacterial surfaces, through to anti-fogging and self-cleaning processes Properties Applications Limitations ➢ High refractive index ➢ High efficient photo catalytic activity ➢ Resistance to photo corrosion ➢ Chemical stability ➢ Low cost ➢ Non-toxicity ➢ High mechanical strength ➢ White pigment in paints and paper ➢ Bone implant material ➢ Ultra-violet absorber in sunscreen ➢ Cosmetic products ➢ Additive in food products ➢ Environmentally friendly material ➢ a wide band gap (3.2 eV), can use only (∼5%) of the available solar energy ➢ higher electron hole recombination rate INTRODUCTION TO TiO2 PHOTO CATALYST 4
- 5. VISIBLE LIGHT-ACTIVATED TiO2 ➢ Metal ion doping (Cu, Co, Ni, Cr,Mn, Mo, Nb, V, Fe, Ru, Au, Ag, Pt) ➢ Non-metal doping (N, S, C, B, P, I, F) Metal Doping ➢ Disperses the metal nanoparticles in TiO2 matrix as substitutional or interstitial impurity ➢ Excites the electrons from the created defect states to the conduction band states of TiO2 ➢ Changes the surface properties like surface area and surface acidity of TiO2 catalyst Benefits Of Metal Doping ➢ Red-shift in the absorption spectra ➢ Improved trapping of electrons to inhibit electron hole recombination during irradiation ➢ Has higher activity in photo degradation of dyes under visible light ➢ Antibacterial activity, microbial treatment and super hydrophilicity 5 Elemental doping enhances visible-light absorption and reduces band gap energy
- 6. Microstructural changes like decreased crystallite size, larger surface area, bigger particle size of metal doped TiO2 nanoparticles shifts its optical absorption edge to visible-light region and consequently utilizes more visible light energy than the pure TiO2 nano particles Longer wavelength exploitation reduces the excitonic energy gap The redshift of doped TiO2 particles is attributed to the charge transitions from impurity level to the TiO2 conduction band and it permits the study of photocatalytic activity under visible light Optical Absorption And Band Gap Modification In Tio2 upon Metal Doping Eg -minimum energy required for valence electrons to move up to conduction band, Pure TiO2-3.2eV Doping creates new electronic states in band gap of TiO2 which modifies the conduction band minima and valence band maxima and leads to band gap reduction 6
- 7. PHOTOCATALYTIC MECHANISM Catalyst -A substance which accelerates a chemical reaction without being consumed as a reactant Photocatalyst -A substance which modifies or accelerates the rate of chemical reaction under irradiation of light Mechanism -When incident light of energy equal to greater than the bandgap, induces the generation of electron-hole pair and the excited electrons or holes diffuses to the surface and creates two oxidation reactants – hydroxyl radicals .OH and superoxide anion O2 -.These reactants decompose toxic organic substance to non-toxic organic compounds such a carbon, water, ammonium, nitrates and chloride ions 1.Photo Excitation (Electron-hole pair generation) 𝑇𝑖𝑂2 = ℎ + +𝑒 − 2.Ionization of water (Holes react with the surface attached H2O or OH− of pollutant to produce the hydroxyl radical) 𝐻2 𝑂 + ℎ + → 𝐻 + +𝑂𝐻• 3.Oxygen ionosorption the electrons are congregated by oxygen to produce oxide radicals 𝑂2 + 𝑒− → 𝑂2 − 4. Protonation of superoxide 𝑂2 − + 𝐻𝑂• → 𝐻𝑂𝑂• 𝐻𝑂𝑂• + 𝑒− → 𝐻𝑂2 − 𝐻𝑂2 − + 𝐻+ → 𝐻2 𝑂2 𝐻2 𝑂2 → 𝐻𝑂• 𝐻𝑂• + 𝐷𝑦𝑒 → 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑠 + 𝐻2O Oxidation process Reduction process Photocatalytic Process-Steps Involved 7
- 8. ➢In TiO2 photocatalyst, excitons undergo successive oxidation and reduction reactions with organic pollutants, which are adsorbed on the surface of the catalyst to give the non toxic constituents ➢By utilizing the strong oxidation strength of hydroxyl radical, photocatalytic oxidation disinfect, deodorize, and purify air, water, and different surface areas PHOTOCATALYTIC PERFORMANCE OF TiO2 8
- 9. Factors Affecting Efficiency Of Metal Doped Tio2 Photocatalyst 1.Photocatalyst Quantity 2.Additive concentration 3.Dye concentration 4.pH of reaction mixture 5.Size and shape of nano photocatalyst 6.Reaction temperature 7.Light Intensity and illumination time 8.Nature of pollutants 9.Surface area of the photocatalyst nano particles 9 Experimental Outcome ➢ The decrease in absorption peak of organic pollutant shows degradation of the substance into non toxic substituents ➢ With the extended illumination period, the degradation is higher ➢ The doped TiO2 nano particles show the highest percentage of degradation than that of pure TiO2 Photocatalytic Efficiency Photocatalytic efficiency is defined as the number of degraded molecules formed per one quantum of light that is being absorbed by the photocatalytic system
- 10. ➢ Doping not only increases the lifetime of charge carriers but it also increases the visible light absorption due to shortened band gap ➢ Reduced band gap energy and increased surface roughness (reaction sites) due to the stimulated point defects improves the catalytic efficiency of metal doped TiO2 ➢ the larger surface area facilitates the nano particles to have more adsorption site and support well the binding of organic molecules with the surface of nanoparticles and quicken the splitting of pollutant molecules ➢ Thus, concentration and valence of the metal dopant strongly determine the photocatalytic activity of doped TiO2 nanoparticles ➢ The observed characteristics promotes TiO2 nano particles as a suitable medium for water filtration and purification. CONCLUSION 10
- 11. 11 References 1. Anila Ajmal, Imran Majeed, Riffat Naseem Malik, Hicham Idriss and Muhammad Amtiaz Nadeem, “Principles and mechanisms of photocatalytic dye degradation on TiO2 based photocatalysts: a comparative overview”, RSC Adv., 2014, 4, 37003–37026 | 2. R. Saravanan, Francisco Gracia and A. Stephen, Basic Principles, Mechanism,and Challenges of Photocatalysis”, Springer International Publishing AG 2017 M.M. Khan et al. (eds.), Nanocomposites for Visible Light-induced Photocatalysis, Springer Series on Polymer and Composite Materials, DOI 10.1007/978-3-319-62446-4_2 3. M. Manzoor · A. Rafiq · M. Ikram · M. Nafees · S. Ali, “Structural, optical, and magnetic study of Ni-doped TiO2 nanoparticles synthesized by sol–gel method”, International Nano Letters (2018) 8:1–8 4. Kumar A, Pandey G. A review on the factors affecting the photocatalytic degradation of hazardous materials. Material Sci & Eng Int J. 2017;1(3):106-114 5. Ambrus Z, Balazs N, Alapi T, Wittmann G, Sipos P, Dombi A, Mogyorosi K, Synthesis, Structure and Photocatalytic Properties of Fe(III)–Doped TiO2 Prepared from TiCl3. Applied Catalysis B: Environmental 2008;81 27–37 6. Saleem A, Imran M, Shahzadi A, Junaid M, Majeed H, Rafiq A and Ali S (2019) Drastic improvement in catalytic, optical and visible- Light photocatalytic behavior of cobalt and nickel doped TiO2 nanopowder. Materials Research Express 6:015003 1-10. 7. Paul S and Choudhary A (2014) Investigation of the optical property and photocatalytic activity of mixed phase nanocrystalline titania. Appl Nanosci 4:839–847. 8. Maurya A, Chauhan, P, Mishra S K and Srivastava R K (2011) Structural, optical and charge transport study of rutile TiO2 nanocrystals at two calcination temperatures. Journal of Alloys and Compounds 509(33): 8433–8440 9. Inturi SNR, Boningari T, Suidan M and Smirniotis P G (2014) Visible-light-induced photodegradation of gas phase acetonitrile using aerosol-made transition metal (V, Cr, Fe, Co, Mn, Mo, Ni, Cu, Y, Ce, and Zr) doped TiO2. Appl. Catal. B Environ. 144: 333–42. 10. R Vidhyaa, R Gandhimathib, M Sankareswaria & K Neyvasagamc , “Influence of Cu concentration on the structural, morphological, optical and catalytic properties of TiO2 thin films”, Indian Journal of Pure & Applied Physics Vol. 57, July 2019, pp. 475-482 11. Vidhya Rajendran, Gandhimathi Rajendran, Neyvasagam Karuppathevar, “Phtotocatalytic Degradation of Methyelene Blue by Cu Doped TiO2 Thin Films under Visible Light Irradiation”, Mechanics, Materials Science & Engineering, 2017 – ISSN 2412-5954406 12. Howard C J, Sabine T M, Dickson F “ Structural and thermal parameters for rutile and anatase” Acta crystallographica B47 (1991) 462-468
- 12. Thank you 12