Modified titanium dioxide (tio2) photocatalysts for the degradation of organic pollutants in wastewater

MODIFIED TITANIUM DIOXIDE (TiO2) PHOTOCATALYSTS FOR THE DEGRADATION OF ORGANIC POLLUTANTS IN WASTEWATER ZHOU JINKAI (M.Eng, BICT) A THESIS SUBMITTED FOR THE DEGREE OF PhD OF ENGINEERING DEPARTMENT OF CHEMICAL AND BIOMOLECULAR ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2007 Acknowledgement I would like to convey my deepest appreciation to my supervisors, Assoc Prof Zhao X S., George and Prof Ajay K Ray, for their constant encouragement, invaluable guidance, patience and understanding throughout the whole length of my PhD candidature This project had been a tough but enriching experience for me in research I would like to express my heartfelt thanks to Dr Zhao and Dr Ray for their guidance on writing scientific papers including PhD thesis I am grateful to Prof Masakazu Anpo, for his support during my stay in Japan for the research cooperation and Prof Zou Zhigang, for his kindly advice and guidance during my stay in China for the research collaboration for this PhD project I would also like to take this opportunity to acknowledge Prof Zeng Huachun, Prof Bai Renbi, the members of my PhD committee, for offering suggestions and comments I would like to express my sincerest appreciation to the Department of Chemical and Biomolecular Engineering for offering me the chance of studying at NUS with a scholarship I am grateful to my parents and other family members for their continuous support during my PhD study Special thanks are given to all of my lab mates and friends: Zhang Yan, Eng Yong Yong, Zhang Yuxin, Su Fabing, Lv Lu, Bao Xiao Ying, Lee Fang Yin, Wang Likui, Li Gang, Liu Jiajia, Tian Xiaoning, and Bai Peng who help me in different ways in my work and make my staying in NUS more enjoyable Particular acknowledgement goes to Mr Chia Phai Ann, Mr Shang Zhenhua, Dr Yuan Zeliang, Dr Rajarathnam D., Ms Lee Chai Keng, Ms Tay Choon Yen, Mdm Jamie Siew, Miss Sylvia Wan for their kind supports in experiments ii Table of Contents Acknowledgement ………………………………………….…………………… … ii Table of Contents .iii Summary… …… ………………………………………….……….………….… ix Nomenclature ………………………………………………………………….… xi List of Tables …….…………………………………………………………….….xiii List of Figures .……………………………………………………………… xiv List of Schemes .………………………………………………………….…… xx Chapter Introduction …………………………………………….……….…1 1.1 Wastewater treatment ………………………… ………………… ….…1 1.2 Photocatalysis for wastewater treatment…………………….…….…….…4 1.3 Semiconductor photocatalysts………………………….………… …….…6 1.4 Visible-light-active photocatalysts……………………………….……….…8 1.5 Objectives and scope of this thesis work………………………………… 10 1.6 Structure of thesis………………………………………………………… 10 Chapter Literature Review ……………….….……………….………….12 2.1 Principle of photocatalysis………………………… 12 2.1.1 Heterogeneous photocatalysis…….…………………………….….…12 2.1.2 Choice of photocatalyst and TiO2……………… …………….… …15 2.1.3 Radiation sources…………………………………………………… 17 2.2 Mechanism of semiconductor photocatalysis… …………….………… 18 2.2.1 General mechanism of semiconductor photocatalysis reaction…….…19 2.2.2 Surface chemistry of metal oxide semiconductors …………….…….21 iii 2.2.3 Formation of reactive oxygen species……………………….…… …23 2.3 Kinetic aspects of semiconductor photocatalysis…………… ………… 26 2.3.1 Kinetics of semiconductor photocatalysis… ……………………… 26 2.3.2 Kinetic model of semiconductor photocatalysis…………………… 28 2.4 Semiconductor photocatalysis for the removal of organic pollutants … 29 2.5 Properties of TiO2 photocatalysts………………………………….… … 31 2.5.1 Structural properties………………………………………………… 31 2.5.2 Electronic properties……………………………….…………….… 32 2.5.3 Photocatalytic properties………………………… …………… … 35 2.6 Modification of TiO2 photocatalysts………………………………… ….38 2.6.1 Metal ion implantation or metal doping method……………… …….39 2.6.2 Nonmetal doping method………………………….…………… … 42 2.6.3 Formation of new binary oxides………………… ……….….…… 43 2.6.4 Formation of solid solution……………………… ……….……… 44 2.7 Photoreactor simulation………………………………………….…… …45 Chapter Photodegradation of Benzoic Acid over Metal-doped TiO2 under UV-light Irradiation (λ < 380 nm)……………………………… …50 3.1 Introduction…………………………………………………………… ….50 3.2 Experimental Details……………………………………… …………… 52 3.2.1 Synthesis of metal-doped TiO2 ……………… ……………… … 52 3.2.2 Characterization of metal-doped TiO2………… ………………… 53 3.2.3 Evaluation of photocatalytic activities of metal-doped TiO2… ……54 3.3 Results and discussion ………………………………………………….… 56 3.3.1 Structure and morphology…………………………………………….56 iv 3.3.2 UV-vis/diffuse reflectance spectra…………………………… …… 60 3.3.3 X-ray Photoelectron spectroscopy (XPS) ………………………… 61 3.3.4 Point of zero charge (PZC)………………………… ……………… 62 3.3.5 Photoluminescence……………… ….……………………………….64 3.3.6 Fluorescence decay profile……………………………… …….…….66 3.3.7 Raman spectroscopy………………………………………………… 68 3.3.8 Evaluation of photocatalytic actvities……………………….……… 70 3.4 Conclusion……………………………………………………………… .79 Chapter Flowerlike F-doped TiO2 Photocatalyst for MB Degradation under Visible Light Irradiation (λ > 420 nm)……… … 80 4.1 Introduction ……………………………………………………………… 80 4.2 Experimental details…………………….……………………………… 83 4.2.1 Synthesis of flowerlike F-doped TiO2 hollow microspheres ……… 83 4.2.2 Characterization……………………….………………………… … 83 4.2.3 Photocatalytic activity evaluation ………………………………… 84 4.3 Results and discussion………………………………………………… ….84 4.3.1 X-ray diffraction (XRD)…………………………………………… 84 4.3.2 UV-vis/DRS…………………………………………………….… 85 4.3.3 XPS………………………………………………………………… 88 4.3.4 Field Emission Scanning Electron Morphology (FESEM)………… 90 4.3.5 Transmission Electron Microscopy (TEM)………………………….91 4.3.6 Photoactivities evaluation……………………………………………96 4.4 Conclusion………………………………………………………………….103 v Chapter Bismuth Titanate Bi12TiO20 as Photocatalyst for Methanol Degradation under Visible Light Irradiation (λ > 440 nm)…….… 104 5.1 Introduction …………………………………………………………….…104 5.2 Experimental details …………………………………………………… 107 5.2.1 Synthesis of Bi12TiO20………………………………………….… 107 5.2.2 Characterization of Bi12TiO20…………………………………… 107 5.2.3 Calculation of band structure …………………………………… 108 5.2.4 Evaluation of photocatalytic activities………………………… 108 5.3 Results and discussion……………………………………………… … 109 5.3.1 XRD……………………………………………………………… 109 5.3.2 HRTEM…………………………………………………… …… 111 5.3.3 UV-vis/DRS……………………………………………………… 111 5.3.4 Band Structure and DOS………………………………………… 114 5.3.5 FT-IR and FT-Raman spectroscopy ………………………….… 116 5.3.6 Photocatalytic activities………………………………… ……… 118 5.4 Conclusion………………………………………………………… …… 124 Chapter Modification of TiO2 by Ion Implantation and its Photoactivity under Visible Light Irradiation (λ > 450 nm)…… ….125 6.1 Enhancement of the photoactivity of P25 TiO2 by vanadium ion implantation method……………………………………………………………….125 6.1.1 Introduction………………………………………………………….125 6.1.2 Experimental details…………………………………………………127 6.1.3 Results and discussion……………………………………………….128 6.1.4.Conclusion……………………………………………………………135 vi 6.2 V-ion-implanted TiO2 thin film by ion cluster beam method….………136 6.2.1 Introduction…………………………………………………………136 6.2.2 Experimental details………………………………….…………… 138 6.2.3 Results and discussion ………………………………….………….139 6.2.4 Conclusion…………………………………………………….…….145 Chapter Simulation of a Taylor Vortex Photoreactor for Degradation of Organic Pollutants……………………………………… 146 7.1 Introduction……………………………………………………………… 146 7.2 Taylor-Couette flow and flow instability…………………………………148 7.3 Problem Formulation and Grid Generation…………………………… 151 7.3.1 Geometric configuration of the photoreactor… … …………… 152 7.3.2 Grid generation procedure………………….……… ………………153 7.3.3 Features of grid………………………………………….………… 154 7.3.4 Mathematical formulation…………………………………… …….156 7.3.5 Discretization………………………………………………….…… 157 7.4 Results and discussion………………………………………………… …160 7.4.1 Analytical stations………………………………………………… 160 7.4.2 Top down symmetry of Taylor-Couette flow………………….……160 7.4.3 Axisymmetry of Taylor-Couette flow……………………………….161 7.4.4 Comparison of axial velocity contours………………………………163 7.4.5 Change of axial velocity with radial coordinate…………………… 165 7.4.6 Change of radial velocity with radial coordinate……………………169 7.4.7 Change of axial and radial velocity with axial coordinate………… 173 7.4.8 Flow development with time with respect to axial velocity…………180 7.5 Conclusion……………………………………………………………….…184 vii Chapter Conclusions and Recommendations…………………….… 185 8.1 Conclusions……………………………………………….……………… 185 8.2 Recommendations…………………………………………………….……187 REFERENCES………………………………………………………………….… 190 PUBLICATIONS……………………………………………………………… .210 APPENDIX……………………………………………………………………… 212 viii Summary The scientific and engineering interest in semiconductor photocatalysis has grown exponentially in the past few years due to its intriguing advantages over other traditional wastewater treatment processes In a typical semiconductor photocatalytic process, a semiconductor photocatalyst is activated by the absorption of a suitable light, thus generating electron-hole pairs, in which holes can oxidize organic compounds while electrons can reduce metal ions present in the wastewater The photoinduced electron-hole pairs can move freely to undergo charge transfer to the adsorbed species on the surface of semiconductor, while they may undergo volume recombination and give off heat Therefore, the successful separation of photoinduced electron-hole pair is very important for photocatalytic reactions Many researches have been done on the investigation of the photoactivity of semiconductors, among which TiO2 has been shown to be the most suitable photocatalyst for widespread environmental applications because it is biologically and chemically inert, resistive to photocorrosion and chemical corrosion, inexpensive and non-toxic Although TiO2 is widely used as a suitable photocatalyst, it mainly absorbs ultra-violet light due to its large bandgap energy (3.2 eV), giving rise to a very low energy efficiency Therefore, it is of great significance to modify the electronic structure and surface property of TiO2 so as to use visible light effectively In this thesis work, several methods were used to modify TiO2 with a primary objective of developing visible-light-responsive TiO2-based photocatalysts The photocatalytic activities of the catalysts were investigated for the degradation ofa couple of organic compounds under visible light irradiation Meanwhile, the design and simulation of a Taylor Vortex Photoreactor was conducted ix The sol-gel method was employed to dope metals into TiO2 The photocatalytic data for the degradation of benzoic acid showed that the modified TiO2 photocatalysts displayed activities only under UV light irradiation F-doped TiO2 photocatalysts with a flower-like morphology were prepared by a one-pot hydrothermal synthesis method The photocatalytic results for the degradation of methylene blue under visible light irradiation showed that while doping of F did not shift the optical absorption edge to the visible light region, F-doped TiO2 showed photoactivities under visible light irradiation because of the presence of defects due to interstitial substitution of O by F Polycrystalline Bi12TiO20 photocatalyst, which is responsive to visible light irradiation below 500 nm, was prepared by a simple solid-state reaction method Its photocatalytic activity was investigated by using photooxidation of methanol The observed high photocatalytic activity of Bi12TiO20 is attributed to its band structure, in which hybridization of Bi 6s with O 2p increases the mobility of photogenerated carriers Vion-implanted P25 TiO2 pellets and thin films were also prepared by the metal ion implantation and ion cluster beam methods They were observed to be photocatalytically active for the degradation of formic acid under visible light irradiation (λ> 450 nm) A Taylor Vortex Photoreactor was designed and simulated using a commercial software FLUENT® The reactor consists of two co-axial cylinders When the inner cylinder is rotated at a certain speed, the unsteady flow within the annulus allows the fluids to recirculate from the vicinity of the rotating inner cylindrical surface to the stationary outer cylindrical surface of an annulus Such arrangement helps minimize the mass transfer resistance Keywords: Photocatalysis, wastewater treatment, metal-doped TiO2, F-doped TiO2, Bi12TiO20 photocatalyst, V-ion-implanted TiO2, Taylor Vortex Photoreactor x References performance of supported photocatalysts for water detoxification processes, Catalysis Today, 54, pp.143-157 1999 Pruden, A L and D F Ollis Degradation of chloroform by photoassisted heterogeneous catalysis in dilute aqueous suspensions of TiO2, Environ Sci Technol., 17, pp.628-631 1983 Rahman, N M.; K M Krishna; T Soga; T Jimbo and M Umeno Optical properties and X-ray photoelectron spectroscopic study of pure and Pb-doped TiO2 thin films J Phys Chem Solids, 60, pp.201-210 1999 Rayleigh, L On the Dynamics of Revolving Fluids Scientific Papers, Cambridge, England, 6, pp.447-453 1920 Reutergardh, L B and M Iangphasuk Photocatalytic Decolorization of Reactive Azo Dye: A Comparison between TiO2 and CdS Photocatalysis Chemosphere, 35, pp.585596 1997 Rhoderick, E H and R H Williams Metal-Semiconductor Contacts, 2nd Ed., Oxford University Press: New York, 1988 Robert, D., A Piscopo, O Heintz and J V Weber Photocatalytic detoxification with TiO2 supported on glass-fibre by using artificial and natural light, Catalysis Today, 54, pp.291-296 1999 Sakatani, Y.; H Ando; K Okusako and H Koike Metal ion and N co-doped TiO2 as a visible-light photocatalyst J Mater Res., 19, pp.2100-2108 2004 Sakthivel, S and H Kisch, Daylight Photocatalysis by Carbon-Modified Titanium Dioxide, Angew Chem Int Ed., 42, pp.4908-4911 2003 Sato, J.; H Kobayashi and Y Inoue Photocatalytic activity for water decomposition of indates with octahedrally coordinated d10 configuration II Roles of geometric and electronic structures J Phys Chem B, 107, pp.7970-7975 2003 Schacht, S.; Q Huo; I G Voigt-Matin; G D Stucky and F Schuth Oil-water interface templating of mesoporous macroscale structures, Science, 273, pp.768-771 1996 Sclafani, A., M.- N Mozzanega and P Pichat Effect of silver deposits on the photocatalytic activity of titanium dioxide samples for the dehydrogenation or oxidation of 2-propanol, J Photochem Photobiol., A : Chem., 59, pp.181-188 1991 Sclafani, A and J M Herrmann Comparison of the Photoelectronic and Photocatalytic Activities of Various Anatase and Rutile Forms of Titania in Pure Liquid Organic Phases and in Aqueous Solution, J Phys Chem., 100, pp.1365513661 1996 203 References Serpone, N.; D Lawless; J Disdier and J.-M Herrmann Spectroscopic, photoconductivity and photocatalytic studies of TiO2 colloids: naked and with the lattice doped with Cr3+, Fe3+ and V5+ cations, Langmuir, 10, pp.643-648 1994 Serpone, N.; D Lawless and R Khairutdinov Size effects on the photophysical properties of colloidal anatase TiO2 particles: size quantization or direct transitions in this indirect semiconductor J Phys Chem., 99, pp.16646-16652 1995 Serpone, N.; G Sauve; R Koch; H Tahiri; P Pichat; P Piccinini; E Pelizzetti and H Hidaka Standadization Protocol of Process Efficiencies and Activation Parameters in Heterogeneous Photocatalysis: Relative Photonic Efficiencies J Photochem Photobiol A: Chem., 106, pp.191-203 1996 Singhal, B., A Porwal, A Sharma, R Ameta and S.C Ameta Photocatalytic Degradation of Cetylpyridinium Chloride over Titanium Dioxide Powder J Photochem Photobiol A: Chem., 108, pp.85-88 1997 Sivalingam, G ; K Nagaveni; M S Hegde and G Madras Photocatalytic degradation of various dyes by combustion synthesized nano anatase TiO2 Appl Catal., B : Environ., 45, pp.23-38 2003 So, W.W., S.B Park, K.J Kim, C.H Shin and S.J Moon The crystalline phase stability of titania particles prepared at room temperature by the sol-gel method J Mater Sci., 36, pp.4299-4305 2001 Sooklal, K.; B S Cullum; S M Angel and C J Murphy Photophysical Properties of ZnS Nanoclusters with Spatially Localized Mn2+, J Phys Chem., 100, pp.4551-4555 1996 Stathatos, E.; P Lianos; P Falaras and A Siokou Photocatalytically deposited silver nanoparticles on mesoporous TiO2 films, Langmuir, 16, pp.2398-2400 2000 Suda, Y and T Morimoto Molecularly Adsorbed H2O on the Bare Surface of TiO2 (rutile), Langmuir, 3, pp.786-788 1987 Sun, Y.; B Mayers and Y Xia Metal Nanostructures with Hollow Interiors, Adv Mater., 15, pp.641-646 2003 Suzuki, K.; G Bley; U Neukirch; J Gutowski; N Takojima; T Sawada and K Imai Stretched-exponential decay of the luminescence in ZnSe-ZnTe superlattices Solid State Commun., 105, pp.571-576 1998 Takeda, N.; M Ohtani; T Torimoto; S Kuwabata and H Yoneyama Evaluation of Diffusibility of Adsorbed Propionaldehyde on Titanium Dioxide-Loaded Adsorbent Photocatalyst Films from its Photodecomposition Rate, J Phys Chem B, 101, pp.2644-2649 1997 204 References Takeuchi, M.; H Yamashita; M Matsuoka; M Anpo; T Hirao; N Itoh and N Iwamoto Photocatalytic decomposition of NO under visible light irradiation on the Cr-ion-implanted TiO2 thin film photocatalyst Catal Lett., 67, pp.135-137 2000 Tang, J.; Z Zou and J Ye Efficient photocatalytic decomposition of organic contaminants over CaBi2O4 under visible-light irradiation, Angew Chem Int Ed., 43, pp.4463-4466 2004 Tao, X.; W Ma; T Zhang and J Zhao Efficient photooxidative degradation of organic compounds in the presence of iron tetrasulfophthalocyanine under visible light irradiation Angew Chem Int Ed., 40, pp.3014-3018 2001 Taylor, G I Stability of a Viscous Liquid Contained between Two Rotating Cylinders, Philos Trans Roy Soc Lond A, 223, pp.289-343 1923 Titirici, M.-M.; M Antonietti and A Thomas, A Generalized Synthesis of Metal Oxide Hollow Spheres using a Hydrothermal Approach, Chem Mater., 18, pp.38083812 2006 Tsuji, I., H Kato, H Kobayashi and A Kudo Photocatalytic H2 Evolution Reaction from Aqueous Solutions over Band Structure-controlled (AgIn)xZn2(2-x)S2 Solid Solution Photocatalysts with Visible-light Response and Their Surface Nanostructures, J Am Chem Soc., 126, pp.13406-13413 2004 Tsumura, T.; N Kojitan; I Izumi; N Iwashita; M Toyoda and M Inagaki Carbon coating of anatase-type TiO2 and photoactivity J Mater Chem., 12, pp.1391-1397 2002 Turchi, C S and D F Ollis Mixed Reactant Photocatalysis J Catal., 119, pp.483496 1989 Turchi, C S and D F Ollis Photocatalytic Degradation of Organic Water Contaminants: Mechanisms Involving Hydroxyl Radical Attack J Catal., 122, pp.178-192 1990 Umebayashi, T.; T Yamaki; S Tanaka and K Asai Visible Light-Induced Degradation of Methylene Blue on S-doped TiO2 Chem Lett., 32, pp.330-331 2003 Vasconcelos, I F.; M A Pimenta and A S B Sombra Optical properties of Bi12SiO20 (BSO) and Bi12TiO20 (BTO) obtained by mechanical alloying J Mater Sci., 36, pp.587-592 2001 205 References Wang, C M and T E Mallouk Wide-range tuning of the titanium dioxide flat-band potential by adsorption of fluoride and hydrofluoric acid, J Phys Chem., 94, pp.4276-4280 1990 Wang, C C.; Z Zhang and J Y Ying Photocatalytic decomposition of halogenated organics over nanocrystalline titania Nanostruct Mater., 9, pp.583-586 1997 Wang, Z.; X F Qian; J Yin and Z K Zhu Large-Scale Fabrication of Tower-like, Flower-like, and Tube-like ZnO Arrays by a Simple Chemical Solution Route, Langmuir, 20, pp.3441-3448 2004 Werely, S T and R M Lueptow Spatio-temporal Character of Non-wavy and Wavy Taylor Couette Flow, J Fluid Mech., 364, pp.59-80 1998 Wu, T.; G Liu; J Zhao; H Hidaka and N Serpone Evidence for H2O2 Generation during the TiO2-Assisted Photodegradation of Dyes in Aqueous Dispersions under Visible Light Illumination, J Phys Chem B, 103, pp.4862-4867 1999 Xu, A W.; Y Gao and H Q Liu The preparation, characterization and their photocatalytic activities of rare-earth-doped TiO2 nanoparticles, J Catal., 207, pp.151-157 2002 Xu, Z.; J Shang; C Liu; C Kang; H Guo and Y Du The preparation and characterization of TiO2 ultrafine particles Mater Sci Eng., B, 56, pp.211-216 1999 Yamashita, H.; Y Ichihashi; M Harada; G Stewart; M A Fox and M Anpo Photocatalytic Degradation of 1-Octanol on Anchored Titanium Oxide and on TiO2 Powder Catalysts, J Catal., 158, pp.97-101 1996 Yamashita, H.; M Harada; A Tanii; M Honda; M Takeuchi; Y Ichihashi; M Anpo; N Iwamoto; N Itoh and T Hirao Preparation of Efficient Titanium Oxide Photocatalysts by an Ionized Cluster Beam (ICB) Method and their Photocatalytic Reactivities for the Purification of Water, Catal Today, 63, pp.63-69 2000 Yamashita, H.; M Harada; J Misaka; M Takeuchi; B Neppolian and M Anpo Photocatalytic degradation of organic compounds diluted in water using visible lightresponsive metal ion-implanted TiO2 catalysts: Fe ion-implanted TiO2 Catal Today, 84, pp.191-196 2003 Yamashita, H and M Anpo Application of an Ion Beam Technique for the Design of Visible Light-Sensitive, Highly Efficient and Highly Selective Photocatalysts: IonImplantation and Ionized Cluster Beam Methods, Catal Surv Asia, 8, pp.35-45 2004 Yamashita, H.; M Takeuchi and M Anpo Visible-light-sensitive photocatalysts Encyclopedia of Nanoscience and Nanotechnology, 10, pp.639-654 2004a 206 References Yang, J.; L Qi; C Lu; J Ma and H Cheng Morphosynthesis of Rhombododecahedral Silver Cages by Self-Assembly Coupled with Precursor Crystal Templating, Angew Chem., Int Ed., 44, pp.598-603 2005 Yang, H G and H C Zeng, Self-aligned Growth of Hexagonal TiO2 Nanosphere Arrays on α-MoO3 (010) Surface, Chem Mater., 15, pp.3113-3120 2003a Yang, H G and H C Zeng, Control of Nucleation in Solution Growth of Anatase TiO2 on Glass Substrate, J Phys Chem B, 107, pp.12244-12255 2003b Yang, H G and H C Zeng, Preparation of Hollow Anatase TiO2 Nanospheres via Ostwald Ripening, J Phys Chem B, 108, pp.3492-3495 2004 Yao, W F.; H Wang; S S Xia; X H Xu; X N Yang; D Wang and M Wang Preparation and characterization of bismuth titanate Bi12TiO20 nanocrystals J Mater Sci Lett., 21, pp.1803-1805 2002 Yao, W F.; H Wang; X H Xu; X F Cheng; J Huang; S X Shang; X N Yang and M Wang Photocatalytic property of bismuth titanate Bi12TiO20 crystals, Appl Catal A: General, 243, pp.185-190 2003 Yeung, K L.; S T Yau; A J Maira; J M Coronado; J Soria and P L Yue The influence of surface properties on the photocatalytic activity of nanostructured TiO2 J Catal., 219, pp.107-116 2003 Yin, H., Y Wada, T Kitamura, S Kambe, S Murasawa, H Mori, T Sakata and S Yanagida Hydrothermal synthesis of nanosized anatase and rutile TiO2 using amorphous phase TiO2, J Mater Chem., 11, pp.1694-1703 2001 Yoneyama, H and T Torimoto Titanium dioxide/adsorbent hybrid photocatalysts for photodestruction of organic substances of dilute concentrations Catal Today, 58, pp.133-140 2000 Yu, J C.; J Lin and R W M Kwok Ti1-xZrxO2 Solid Solutions for the photocatalytic Degradation of Acetone in Air, J Phys Chem B, 102, pp.5094-5098 1998 Yu, J C.; J Yu; W Ho; Z Jiang and L Zhang Effect of F- doping on the photocatalytic activity and microstructures of nanocrystalline TiO2 powders Chem Mater., 14, pp.3808-3816 2002 Zang, L., C Lange, I Abraham, S Storck, W F Maier and H Kisch Amorphous Microporous Titania Modified with Platinum(IV) ChloridesA New Type of Hybrid Photocatalyst for Visible Light Detoxification, J Phys Chem B, 102, pp 1076510771 1998 207 References Zhang, Y.; J C Crittenden; D W Hand and D L Perram Fixed-bed photocatalysts for solar decontamination of water, Environ Sci Technol., 28, pp.435-442 1994 Zhang, L and C M Mo Luminescence in nanostructured materials, Nanostruct Mater., 6, pp.831-834 1995 Zhang, Z., C C Wang, R Zakaria and J Y Ying Role of particle size in nanocrystalline TiO2-based photocatalysts, J Phys Chem B, 102, pp.10871-10878 1998 Zhang, Q.; L Gao and J Guo Effects of calcination on the photocatalytic properties of nanosized TiO2 powders prepared by TiCl4 hydrolysis, Appl Catal.B: Environ., 26, pp.207-215 2000 Zhang, W F.; M S Zhang; Z Yin and Q Chen Photoluminescence in anatase titanium dioxide nanocrystals Appl Phys B, 70, pp.261-265 2000 Zhang, T.; T Oyama; A Aoshima; H Hidaka; J Zhao and N Serpone Photooxidative N-demethylation of methylene blue in aqueous TiO2 dispersions under UV irradiation, J Photochem Photobiol A: Chem., 140, pp.163-172 2001 Zhang, D.; D Yang; H Zhang; C Lu and L Qi, Synthesis and Photocatalytic Properties of Hollow Microparticles of Titania and Titania/Carbon Composites Templated by Sephadex G-100, Chem Mater., 18, pp.3477-3485 2006 Zhao, W.; C Chen; X Li; J Zhao; H Hidaka and N Serpone, Photodegradation of Sulforhodamine-B Dye in Platinized Titania Dispersions under Visible Light Irradiation: Influence of Platinum as a Functional Co-catalyst, J Phys Chem B, 106, pp.5022-5028 2002 Zhao, W.; W Ma; C Chen; J Zhao and Z Shuai Efficient degradation of toxic organic pollutants with Ni2O3/TiO2-xBx under visible irradiation J Am Chem Soc., 126, pp.4782-4783 2004 Zhong, Z Y.; Y D Yin; B Gates and Y N Xia Preparation of Mesoscale Hollow Spheres of TiO2 and SnO2 by Templating Against Crystalline Arrays of Polystyrene Beads, Adv Mater., 12, pp.206-209 2000 Zhou, J.; M Takeuchi; X S Zhao; A K Ray and M Anpo Photocatalytic decomposition of formic acid under visible light irradiation over V-ion-implanted TiO2 thin film photocatalysts prepared on quartz substrate by ionized cluster beam (ICB) deposition method Catal Lett., 106, pp.67-71 2006 Zhu, J.; W Zheng; B He; J Zhang and M Anpo Characterization of Fe-TiO2 photocatalysts synthesized by hydrothermal method and their photocatalytic reactivity 208 References for photodegradation of XRG dye diluted in water J Mol Catal A: Chem., 216, pp.35-43 2004 Zou, Z.; J Ye; K Sayama and H Arakawa Direct splitting of water under visible light irradiation with an oxide semiconductor photocatalyst Nature, 414, pp.625-627 2001 209 Publications Publications List of publications coming from this thesis work Papers published (or in press) in international refereed journal J Zhou, M Takeuchi, X S Zhao, A K Ray, M Anpo Photocatalytic decomposition of formic acid under visible light irradiation over V-ion-implanted TiO2 thin film photocatalysts prepared on quartz substrate by ionized cluster beam (ICB) deposition method Catalysis Letters 2006, 106: 67-70 J Zhou, Y Zhang, X S Zhao, A K Ray Photodegradation of benzoic acid over metal-doped TiO2 Industrial & Engineering Chemistry Research 2006, 45: 3503-3511 J Zhou, Z Zou, X S Zhao, A K Ray Preparation and characterization of polycrystalline bismuth titanate Bi12TiO20 (BTO) prepared by a solid-state reaction and its photocatalytic properties under visible light irradiation Industrial & Engineering Chemistry Research 2007 In press J Zhou, X.S Zhao, A K Ray, and M Anpo Enhancement of photocatalytic activity on photodecomposition of formic acid over V-ion-implanted P25 under visible light irradiation, J Colloid & Interface Sci., 2007 In press Papers submitted to international refereed journal J Zhou, X S Zhao, and Ajay K Ray Direct synthesis of self-organized polycrystalline flowerlike F-doped TiO2 hollow microspheres and its photocatalytic activity under visible light irradiation, Chem Mater., 2007 (to be submitted) Book chapter: J Zhou and X S Zhao Environmentally Benign Catalysts: Applications of Titanium Oxide-based Photocatalysts, ed by P Kamat and M Anpo, Springer 2007 (In Preparation) Presentations and abstracts published in conference proceedings Zhou J Zhang Y., Zhao X S., and A K Ray Photodegradation of Benzoic Acid over Metal-doped TiO2 In the Third International Conference on Materials for Advanced Technologies (ICMAT 2005), July 2005, Singapore 210 Publications Zhou J., Takeuchi M., Zhao X.S., Ray A K., and Anpo M Photodecomposition of formic acid over V-ion-implanted TiO2 thin film under visible light irradiation In the Eleventh Asian Chemical Congress/ Thirteenth General Assembly (11th ACC), August 2005, Seoul, Korea 211 Appendix Appendix Experimental data Table A.1 Data for figure 3.11 C/C0 Irradiation Time (min) P25 Undope d TiO2 0.1% Ga-TiO2 0.1% Ag-TiO2 0.1% Cd-TiO2 0.1% Fe-TiO2 0.1% Ni-TiO2 1 1 1 15 0.647 0.6464 0.6216 0.6327 0.8116 0.7798 0.8018 30 0.4314 0.3643 0.2566 0.3332 0.6634 0.6096 0.6911 45 0.184 0.1395 0.0392 0.1363 0.4922 0.4344 0.5863 60 0.0439 0.009 0.0028 0.3794 0.2708 0.5097 212 Appendix Table A.2 Data for figure 3.13 C/C0 Irradiation Time P25 0.05% 0.1% 0.5% 1% TiO2 (min) Undoped Ga-TiO2 Ga-TiO2 Ga-TiO2 Ga-TiO2 1 1 1 15 0.647 0.6464 0.5996 0.6216 0.654 0.7538 30 0.4314 0.3643 0.311 0.2556 0.3885 0.5448 45 0.184 0.1395 0.1124 0.0392 0.1462 0.3275 60 0.0439 0.009 0.0264 0.0514 0.2141 213 Appendix Table A.3 Data for figure 4.8 MB concentration (ppm) Irradiation P25 140 oC 180 oC 220 oC F-TiO2 Time (h) No catalyst F-TiO2 F-TiO2 -0.5 15 15 15 15 15 14.847 14.787 14.186 12.932 13.611 0.5 14.847 14.657 14.109 12.129 - 14.777 14.619 13.553 11.092 13.314 14.637 13.65 13.437 9.589 12.152 14.624 13.237 13.056 8.151 10.544 - 12.591 12.979 7.308 9.33 14.567 12.41 12.946 6.291 8.381 - - 12.83 - 6.483 14.56 12.294 12.746 3.881 4.746 2.941 3.952 214 Appendix Table A.4 Data for figure 4.9 Ln (C/C0) Irradiation 140 oC F-TiO2 180 oC F-TiO2 220 oC F-TiO2 0 0 0.5 0.0054 0.0641 0.0456 0.1535 0.0221 0.0542 0.2991 0.1134 0.083 0.4616 0.2553 0.0889 0.5707 0.3776 0.0915 0.7206 0.4849 Time (h) 215 Appendix Table A.5 Data for figure 5.7 Photocatalysts Yield of CO2 (ppm) P25 2335 BTO-2-500 69 BTO-4-500 110 BTO-0.5-600 782 BTO-1-600 1326 BTO-2-600 1950 BTO-4-600 1486 BTO-0.5-800 294 BTO-1-800 614 BTO-2-800 1222 BTO-4-800 470 Table A.6 Data for figure 5.8 Photocatalysts Yield of CO2 (ppm) P25 54 BTO-0.5-600 312 BTO-1-600 714 BTO-2-600 939 BTO-4-600 470 216 Appendix Table A.7 Data for figure 5.9 Wavelength (nm) λ > 420 Yield of CO2 λ > 440 λ > 480 λ > 500 1950 939 277 65 (ppm) Table A.8 Data for figure 6.5 Yield of CO2 (àmolãg-cat-1) Irradiation 0.44ì10-7 mol/ 2.20ì10-7 mol/ 6.61×10-7 mol/ g-cat V-TiO2 Time (h) P25 g-cat V-TiO2 g-cat V-TiO2 0 0 0.5584 3.6585 15.4231 29.6885 10 0.8213 5.2316 17.1163 35.2386 15 1.0094 6.7865 19.0846 41.6621 20 1.1414 7.1352 20.6408 47.5863 Table A.9 Data for figure 6.8 TiO2 film Yield of CO2 0.1132 V-TiO2/500 oC V-TiO2/700 oC 4.1574 1.5268 (µmol) 217 ... consists of two co-axial cylinders When the inner cylinder is rotated at a certain speed, the unsteady flow within the annulus allows the fluids to recirculate from the vicinity of the rotating inner... toxic organic pollutants In addition, the increasing population of the world is also escalating the requirements of pure water for drinking and household purpose The high population density and the. .. Anpo, for his support during my stay in Japan for the research cooperation and Prof Zou Zhigang, for his kindly advice and guidance during my stay in China for the research collaboration for this