Tài liệu Synthesis of la1 xsrxcoo3 nano photocatalysts using carbonaceous microspheres template and their photocatalytic activities

VIETNAM NATIONAL UNIVERSITY-HOCHIMINH CITY HOCHIMINH CITY UNIVERSITY OF TECHNOLOGY -------------------- VAN-PHUONG DO SYNTHESIS OF La1-xSrxCoO3 NANOPHOTOCATALYSTS USING CARBONACEOUS MICROSPHERES TEMPLATE AND THEIR PHOTOCATALYTIC ACTIVITIES Major of Chemical Engineering Code: 60.52.75 MASTER THESIS HO CHI MINH CITY, 2015 VIETNAM NATIONAL UNIVERSITY-HOCHIMINH CITY HOCHIMINH CITY UNIVERSITY OF TECHNOLOGY -------------------- VAN-PHUONG DO SYNTHESIS OF La1-xSrxCoO3 NANOPHOTOCATALYSTS USING CARBONACEOUS MICROSPHERES TEMPLATE AND THEIR PHOTOCATALYTIC ACTIVITIES Major of Chemical Engineering Code: 60.52.75 MASTER THESIS ADVISOR: MINH-VIEN LE HO CHI MINH CITY, 2015 THE THESIS WAS ACCOMPLISHED AT HOCHIMINH CITY UNIVERSITY OF TECHNOLOGY – VIETNAM NATIONAL UNIVERSTIY-HOCHIMINH CITY Advisor: Dr. Le Minh Vien The primary examiner: Assoc. Prof. Dr. Huynh Ky Phuong Ha The secondary examiner: Assoc. Prof. Dr. Nguyen Dinh Thanh This master thesis was defended at Hochiminh City University of Technology, Vietnam National University-Hochiminh city on July 16th 2015 The master’s thesis committee members are: 1. Assoc. Prof. Dr. Le Thi Kim Phung 2. Assoc. Prof. Dr. Huynh Ky Phuong Ha 3. Assoc. Prof. Dr. Nguyen Dinh Thanh 4. Dr. Nguyen Tuan Anh 5. Dr. Nguyen Khanh Son The thesis committee chairman and the head of major department confirmed that the thesis was corrected. THE COMMITTEE CHAIRMAN HEAD OF DEPARTMENT Assoc. Prof. Dr. Le Thi Kim Phung Prof. Dr. Phan Thanh Son Nam ĐẠI HỌC QUỐC GIA TP. HCM TRƯỜNG ĐẠI HỌC BÁCH KHOA CỘNG HÒA XÃ HỘI CHỦ NGHĨA VIỆT NAM Độc lập – Tự do – Hạnh phúc NHIỆM VỤ LUẬN VĂN THẠC SĨ Họ tên học viên: Đỗ Văn Phương MSHV: 13053242 Ngày, tháng, năm sinh: 23/01/1990 Nơi sinh: Thanh Hóa Chuyên ngành: Kỹ Thuật Hóa Học Mã số: 60.52.75 I. TÊN ĐỀ TÀI: “Synthesis of La1-xSrxCoO3 nano-photocatalysts using carbonaceous microspheres template and their photocatalytic activities” II. NHIỆM VỤ VÀ NỘI DUNG:  Tổng hợp vật liệu perovskite La1-xSrxCoO3 (x = 0, 0.2, 0.4, 0.6, 0.8) bằng phương pháp sol-gel, đánh giá tính chất và khảo sát hoạt tính quang phân hủy xanh methylene  Tổng hợp vật liệu perovskite La1-xSrxCoO3 (với x ứng với vật liệu có bandgap nhỏ nhất) có kích thước nano bằng phương pháp hấp phụ ion bề mặt sử dụng “carbonaceous microspheres” làm chất nền và khảo sát hoạt tính quang phân hủy xanh methylene  Đánh giá và so sánh hoạt tính quang hóa của vật liệu xúc tác La1-xSrxCoO3 tổng hợp bằng phương pháp sol-gel và tổng hợp bằng phương pháp hấp phụ ion bề mặt trong phản ứng khử CO2 để tổng hợp CH4 (với x ứng với vật liệu có bandgap nhỏ nhất). III. NGÀY GIAO NHIỆM VỤ: 19/01/2015 IV. NGÀY HOÀN THÀNH NHIỆM VỤ: 14/06/2015 V. CÁN BỘ HƯỚNG DẪN : TS. Lê Minh Viễn Tp. HCM, ngày . . . . tháng .. . . năm 20.... CÁN BỘ HƯỚNG DẪN CHỦ NHIỆM BỘ MÔN ĐÀO TẠO TS. Lê Minh Viễn PGS. TS. Huỳnh Kỳ Phương Hạ TRƯỞNG KHOA GS. TS. Phan Thanh Sơn Nam ACKNOWLEDGEMENTS I would like to gratefully and sincerely acknowledge my advisor, Dr. Le Minh Vien, for his generous guidance, patience, financial support, and especially, his friendship during the development of my thesis. He also gave me a lot of opportunities to develop my own ability by being allowed to work with such independence during my graduate study at Hochiminh University of Technology. For everything you have done for me, Dr. Vien, I appreciate. I must, however, express my special thanks to all of the lecturers of Inorganic Chemistry Department for giving me a lot of useful advice and support, therefore I could accomplish my thesis on time. I would also like to acknowledge the support of Prof. Jeffrey Chi-Sheng Wu, Department of Chemical Engineering, National Taiwan University for using CO2 reduction photoreactor as well as his valuable contribution. I would like to thank to all of members in our research group for their input, valuable discussion, and accessibilities. In particular, I would like to express my deep gratitude to Ms. Phan Thi Que Phuong and Mr. Ha Duc Huy for their good cooperation, expertise and patience. Finally, and most importantly, I would like to thank to my family, especially my parents, for their faith in me and allowing me to be as ambitious as I wanted. As their encouragements, I gained so much drive and power to rise to the challenge. Actually, I do not know how to express my feeling for best things you have given to me. I ABSTRACT In this research, a series of perovskite-type photocatalysts La1-xSrxCoO3 (x = 0, 0.2, 0.4, 0.6, 0.8) and nanometric photocatalyst La0.6Sr0.4CoO3 have been fabricated by sol-gel method and surface-ion adsorption approach utilizing carbonaceous microspheres as template, respectively. The prepared powders were characterized by some techniques, such as X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Fourier Transform Infra-Red Spectroscopy (FT-IR), Energy Dispersive X-ray spectroscopy (EDX), UV-vis Diffuse Reflection Spectroscopy (UV-vis DRS), and Brumauer – Emmett – Teller (BET). In addition, the effect of La1-xSrxCoO3 powders prepared by two above methods on the photocatalytic degradation of methylene blue and CO2 reduction reaction under UV light source was also investigated. The results showed a maximum photocatalytic degradation of methylene blue solution at 30 ppm could be achieved with a degradation degree of 11.32% by La0.6Sr0.4CoO3 catalyst synthesized at 850 oC for 4h (LSC64-S850), which had lowest band gap (Eg ≈ 2.72 eV) under UV light for 110 min. However, this value was still lower than that of La0.6Sr0.4CoO3 photocatalyst fabricated at 500 oC for 4h using surface-ion adsorption method, LSC64-M500 (Eg ≈ 2.73 eV), which had a uniform particle size of 40 nm – 60 nm in the same condition. Moreover, the photocatalytic results of CO2 reduction reaction indicated that LSC64-M500 catalyst had the methane yield of 103.5 µmol/g which was much higher than that of LSC64-S850, 12.27 µmol/g. II TABLE OF CONTENTS ACKNOWLEDGEMENTS ......................................................................................... I ABSTRACT ................................................................................................................. II TABLE OF CONTENTS .......................................................................................... III TABLE FOR ABBREVIATIONS............................................................................ VI LIST OF FIGURES ................................................................................................ VIII LIST OF TABLES ..................................................................................................... XI INTRODUCTION ........................................................................................................ 1 CHAPTER 1: OVERVIEW......................................................................................... 4 1.1. Photocatalysis ...................................................................................................... 4 1.1.1. Semiconductor .............................................................................................. 4 1.1.2. Definition of photocatalysis ......................................................................... 5 1.1.3. Mechanism of photocatalytic degradation of MB ........................................ 6 1.1.4. Mechanism of photocatalytic degradation of CO2 ....................................... 8 1.2. Perovskite compounds ......................................................................................... 9 1.2.1. Crystal structure ............................................................................................ 9 1.2.2. Physical properties...................................................................................... 11 1.3. Methylene blue .................................................................................................. 13 1.4. Synthesis methods ............................................................................................. 14 1.4.1. Solid-state reaction ..................................................................................... 14 1.4.2. Chemical co-precipitation method ............................................................. 14 1.4.3. Sol-gel method ............................................................................................ 15 1.4.4. Microwave-assisted method ....................................................................... 16 1.4.5. Hydrothermal method ................................................................................. 16 III CHAPTER 2: LITERATURE REVIEW OF LaCoO3 PHOTOCATALYTIC MATERIAL ................................................................................................................ 18 CHAPTER 3: MATERIALS AND EXPERIMENTAL METHODS .................... 25 3.1. The content of research...................................................................................... 25 3.2. Experimental ...................................................................................................... 25 3.2.1. Materials and equipment ............................................................................ 25 3.2.2. Experimental ............................................................................................... 26 3.2.3. Characterization techniques........................................................................ 33 CHAPTER 4: RESULTS AND DISCUSSION ........................................................ 39 4.1. La1-xSrxCoO3 characterization ........................................................................... 39 4.1.1. Perovskite type La1-xSrxCoO3 photocatalysts synthesized by sol-gel method .............................................................................................................................. 39 4.1.2. Carbonaceous microspheres ....................................................................... 42 4.1.3. La0.6Sr0.4CoO3 photocatalysts fabricated by surface-ion adsorption method using carbonaceous microspheres template.......................................................... 44 4.2. Photocatalytic degradation of MB ..................................................................... 48 4.2.1. Calibrate curve of MB ................................................................................ 48 4.2.2. Perovskite type La1-xSrxCoO3 photocatalysts synthesized by sol-gel method .............................................................................................................................. 49 4.2.3. Perovskite type La1-xSrxCoO3 photocatalysts synthesized by surface-ion adsorption method ................................................................................................ 51 4.3. Photocatalytic reduction of CO2 ........................................................................ 53 CHAPTER 5: CONCLUSION AND FUTURE WORK ......................................... 56 5.1. Conclusion ......................................................................................................... 56 5.2. Future work........................................................................................................ 57 REFERENCES ........................................................................................................... 58 IV LIST OF PUBLICATIONS ....................................................................................... 63 CURRICULUM VITAE ............................................................................................ 64 V TABLE FOR ABBREVIATIONS Abbreviation Definition λ Wavelength e- Electron h+ Hole υ Frequency ħ Planck’s constant k Absorption coefficient s Scattering coefficient α Absorption coefficient of the solution l Light path length R The reflectance at the front face C The concentration of solution after irradiation period Co The initial concentration of solution I The transmitted intensity Io The incident intensity T The transmittance XRD X-ray Diffraction SEM Scanning Electron Microscope FT-IR Fourier Transform Infra-Red Spectroscopy EDX Energy Dispersive X-ray spectroscopy UV-vis DRS UV-vis Diffuse Reflection Spectroscopy GC Gas Chromatography BET Brumauer – Emmett – Teller ORR Oxygen Reduction Reaction OER Oxygen Evolution Reaction A The intensity of MB solution after photocatalytic reaction Ao The intensity of MB solution before photocatalytic reaction VI MB VOCs Methylene blue Volatile organic compounds CMs Carbonaceous microspheres LSC28-S850 La0.2Sr0.8CoO3, sol-gel method, 850 oC, 4h LSC46-S850 La0.4Sr0.6CoO3, sol-gel method, 850 oC, 4h LSC64-S850 La0.6Sr0.4CoO3, sol-gel method, 850 oC, 4h LSC82-S850 La0.8Sr0.2CoO3, sol-gel method, 850 oC, 4h LC-S850 LaCoO3, sol-gel method, 850 oC, 4h LSC64-S500 La0.6Sr0.4CoO3, sol-gel method, 500 oC, 4h LSC64-M500 La0.6Sr0.4CoO3, surface-ion adsorption method, 500 oC, 4h LSC64-M550 La0.6Sr0.4CoO3, surface-ion adsorption method, 550 oC, 4h VII LIST OF FIGURES Figure 1. Schematic diagram comparing the actions of a man-made photocatalyst (TiO2) with a natural one (chlorophyll) ......................................................... 6 Figure 2. Schematic diagram of photocatalytic process initiated by photon acting on the semiconductor .......................................................................................... 7 Figure 3. Schematic representation of the photocatalytic reduction of CO2 with H2O on the anchored titanium oxide ...................................................................... 8 Figure 4. Crystal structure of perovskite ..................................................................... 10 Figure 5. Structure formula of methylene blue............................................................ 13 Figure 6. Schematic illustration of the synthetic procedure used to obtain La2O3@CMSs .............................................................................................. 18 Figure 7. The carbonaceous cores removed via calcination at 550 oC for 4h: (a) TEM of products obtained by calcining at 550 oC for 4h; (b) SEM of products obtained by calcining at 550 oC for 4h ........................................................ 19 Figure 8. (a) Time-dependent absorption spectra of methylene blue dye with LaCoO3 hollow spheres catalyst; (b) Plot of MB concentration versus irradiation time for the photodegradation of organic dyes catalyzed LaCoO3 hollow spheres; () and P25 () and the blank without catalyst () under UV irradiation (1, 2, 3, 4, 5, 6 represented the degradation time of 0, 20, 40, 60, 80, 100 min) ................................................................................................. 19 Figure 9. Photocatalytic decomposition of methylene orange over LaCoO3 catalysts calcined at different temperature ................................................................ 20 Figure 10. Photocatalytic degradation of malachite green with La1-xBaxCoO3 (x = 0.1, 0.3, 0.5) catalyst under: (a) UV light and (b) visible light ........................ 21 Figure 11. Reproducibility tests for the catalytic combustion of 2% CO/1% O2 over Cit3 sample as a function of temperature. Conditions: 0.5 g sample, 250 ml/min gas volume flowrate ..................................................................... 22 Figure 12. CO catalyst oxidation quartz reactor, inside a heating mantle, with a thermocouple temperature probe, inserted into the reactor over the catalytic bed ................................................................................................................ 22 VIII Figure 13. (a, c and e): LaCoO3 (b, d, f): C-doped LaCoO3. The yield of formic acid and formaldehyde from photoreduction of CO2 on LaCoO3 and C-doped LaCoO3 under three different radiation source ......................................... 23 Figure 14. Flowchart of La1-xSrxCoO3 synthesis process by the sol-gel method ........ 27 Figure 15. Flowchart of carbonaceous microspheres synthesis process ..................... 28 Figure 16. Flowchart of nano perovskite La0.6Sr0.4CoO3 synthesis process ................ 29 Figure 17. Experimental setup model for the photocatalytic reduction of CO2 .......... 32 Figure 18. Schematic diagram of FTIR spectroscopy instrument ............................... 37 Figure 19. XRD patterns of La1-xSrxCoO3 (x = 0, 0.2, 0.4, 0.6 and 0.8) powders ...... 39 Figure 20. XRD patterns of (a) LSC64-S850 and (b) LSC64-S500 powders ............. 40 Figure 21. EDX image of LSC64-S850 powder.......................................................... 40 Figure 22. SEM image of LSC64-S850 powder.......................................................... 41 Figure 23. UV-vis diffuse absorption spectra of La1-xSrxCoO3 powders .................... 42 Figure 24. SEM image of carbonaceous microspheres synthesized at 170 oC for 11h ...................................................................................................................... 43 Figure 25. FTIR spectrum of carbonaceous microspheres .......................................... 43 Figure 26. XRD patterns of (a) LSC64-M500 and (b) LSC64-M550 ......................... 44 Figure 27. XRD pattern of LaCoO3 product obtained using calcining at 550 oC for 4h ...................................................................................................................... 44 Figure 28. SEM images of LSC64-M500 (left) and LSC64-M550 (right) ................. 46 Figure 29. EDX image of LSC64-M500 ..................................................................... 46 Figure 30. UV-vis diffuse absorption spectra of LSC64-S850 and LSC64-M500 powders ........................................................................................................ 48 Figure 31. Calibrate curve of methylene blue solution ............................................... 49 Figure 32. Degradation of MB (30 mg/L) with different photocatalysts La1-xSrxCoO3 (x = 0, 0.2, 0.4, 0.6, 0.8) under the irradiation of UV light (365 nm) ......... 51 Figure 33. Degradation of MB (10 mg/L) with different photocatalysts LSC64-S850, LSC64-S500, LSC64-M500 and LSC64-M550 under the irradiation of UV light (365 nm) .............................................................................................. 53 IX Figure 34. Influence of LC-S850, LSC64-S850, LSC64-M500 and LSC64-M550 catalysts on the methane yield of CO2 photocatalytic reduction reaction under UV light. ............................................................................................ 54 X LIST OF TABLES Table 1. Information of materials for photocatalyst synthesis .................................... 25 Table 2. Experimental conditions for MB adsorption stage ........................................ 31 Table 3. Experimental conditions of MB degradation stage under UV light .............. 31 Table 4. Weight% and Atomic% of elements of LSC64-S850 catalyst ...................... 41 Table 5. Weight% and Atomic% of elements of LSC64-M500 catalyst ..................... 47 Table 6. MB lost yield of La1-xSrxCoO3 photocatalysts ............................................... 50 Table 7. MB lost yield of LSC64-S500, LSC64-S850, LSC64-M500 and LSC64M550 ............................................................................................................. 52 Table 8. Methane yield of LC-S850, LSC64-S850, LSC64-M550 and LSC64-M500 powders ......................................................................................................... 53 XI INTRODUCTION Pollution causing by dyeing substances has been warned as a serious problem over the world for many year [1]. Today, there are more than ten thousand dyes available commercially and seven lakh tons of dyes are produced annually. Dyes could be of many different structural varieties like acidic, basic, disperse, azo, anthraquinone based and metal complex dyes among others [2]. During the dyeing process a large percentage of the synthetic dye did not bind and was lost to the waste stream. Approximately 10-15% dyes were released into the environment during dyeing process making the effluent highly colored and aesthetically unpleasant [3]. These dyes (especially methylene blue) and other additives were difficult to remove by conventional water treatment procedures and could be transported easily through sewers and rivers because of their high water solubility. They may also undergo degradation to form products that are highly toxic and carcinogenic. Hence, dyes were a potential hazard to living organisms and should be rejected [4]. Besides, the global warming issue was one of the major environmental concerns because of the rising demand for energy which significantly contribute to the increasing of CO2 greenhouse gas emissions [5]. Therefore, a lot of researches have been developed to resolve these serious problems. In recent decades, many advantage technologies have been applied to reduce the effect of these issues such as biology, adsorption and oxidation-reduction method [6]. Based on the report of Fujishima and Honda about the photocatalytic splitting of water into hydrogen and oxygen using TiO2 in 1972 [7], environmental photocatalysis has become a promising and sustainable approach to remove the toxic agents in air and water. In the past years, numerous valuable and cheap photocatalysts were investigated, such as TiO2 [8], ZnO [9], Fe2O3 [10], CdS [11]. However, these photocatalysts had a limitation in use that they can only absorb the ultra-violet light because of their wide band gap [12]. In recent years, various new materials have been successfully fabricated. Among them, perovskite-type oxides (ABO3; A = a rare earth cation and B = a transition metal cation) have attracted considerable attentions due to their unique 1 properties such as various types of oxygen vacancy order, intrinsic oxygen reduction reaction activity, high conductivity and magnetic properties [13]. A number of typical perovskite oxides have been demonstrated as candidate material for photocatalysis, such as SrTiO3 [14], LaCoO3 [15], LaFeO3 [16] and Ba0.5Sr0.5Co0.8Fe0.2O3 [17]. Among perovskite-type photocatalysts, lanthanum cobaltate, LaCoO3, was cheap, environmentally friendly and highly active in oxidation processes, making it a strong promising material for many applications including catalytic reduction of NOx in automotive exhausts, CO2 reduction reaction, catalytic oxidation of volatile organic compounds (VOCs) and photocatalytic degradation reactions [13]. Further researches indicated that the photocatalytic activity of perovskite-base materials could be enhanced by doping. For example, La0.6Sr0.4CoO3 photocatalyst exhibited much higher photocatalytic activity in the 2-propanol degradation than that of pure LaCoO3 [18]. Moreover, Ming Meng (2012) [19] reported that among all the catalysts that fabricated by the simultaneous replacement for La3+ and Co2+ by K+ and Ni3+, the La0.9K0.1Co0.95Ni0.05O3 has the highest performance in NOx removal. In addition, La0.7Ba0.3CoO3 [1] showed optimal photocatalytic activity with a degradation degree of malachite green up to 97% compared to 70.1% of pure LaCoO3 . In 2009, Morteza Baghalha [15] introduced the synthesized perovskite materials had the nominal compositions of LaCoO3, LaCo0.8Cu0.2O3, La0.8Sr0.2Co0.8Cu0.2O3, and La0.8M0.2FeO3 (where M = Ce or Sr). The catalytic activity of the perovskite samples (for lowtemperature CO oxidation) was measured using a quartz reactor with an inlet gas mixture containing 97% N2, 1% O2, and 2% CO. Among them, La0.8Sr0.2Co0.8Cu0.2O3 showed highest activity for CO conversions higher than 80%. However, another serious problem appeared that the photocatalytic performance of LaCoO3 material synthesized using sol-gel method was not good enough for practical application because of its low specific surface area [13]. Luckily, this issue could be resolved if a suitable methodology was applied to reduce the particle size of photocatalyst. Helin Niu (2013) reported that the surface-ion adsorption method could control particle shape of LaCoO3 photocatalyst as well as reduce its particle size, therefore the activity of LaCoO3 material is significantly increased [13]. 2 In this study, perovskite La1-xSrxCoO3 (x = 0, 0.2, 0.4, 0.6, 0.8) photocatalysts were synthesized by sol-gel method and characterized with several techniques such as XRD, SEM and UV-DRS to clearly understand the effect of Sr-doping. Based on these results, the surface-ion adsorption method was applied to increase the specific surface area of photocatalyst because of decreasing the particle size of powder. Finally, the methylene degradation and CO2 reduction reaction were carried out to evaluate the photocatalytic activity of La1-xSrxCoO3 powders prepared by two above methods. 3 CHAPTER 1: OVERVIEW 1.1. Photocatalysis: 1.1.1. Semiconductor: A semiconductor was a substance, usually a solid chemical element or compound that could conduct electricity under some conditions but not others, making it a good medium for the control of electrical current. Its conductance varies depending on the current or voltage applied to a control electrode, or on the intensity of irradiation by infrared (IR), visible light, ultraviolet (UV), or X-rays [20]. The specific properties of a semiconductor depended on the impurities, or dopants, added to it. An N-type semiconductor carried current mainly in the form of negatively-charged electrons, in a manner similar to the conduction of current in a wire. A P-type semiconductor carried current predominantly as electron deficiencies called holes. A hole had a positive electric charge, equal and opposite to the charge on an electron. In a semiconductor material, the flow of holes occurred in a direction opposite to the flow of electrons. Semiconductors were particularly useful as photocatalysts because of a favorable combination of electronic structure, light absorption properties, charge transport characteristics and excited-state lifetimes. A semiconductor, by definition, was nonconductive in its undoped ground state because an energy gap, the band gap, exists between the top of the filled valence band and the bottom of the vacant conduction band. Thus, electron transport between these bands must occur only with appreciable energy change. In semiconductor photocatalysis, excitation of an electron from the valence band to the conduction band was accomplished by absorption of a photon of energy equal to or higher than the bandgap energy of the semiconductor. This lightinduced generation of an electron-hole pair is a prerequisite step in all semiconductormediated photocatalytic processes. Photogenerated species tended to recombine and dissipate energy as heat of photons because the kinetic barrier for the electron-hole recombination process is low. In order to have a photocatalyzed reaction, the e--h+ recombination, subsequent to the initial charge separation, must be prevented as much as possible. However, conduction band electrons and valence band holes could be 4 separated efficiently in the presence of an electric field, such as the one formed spontaneously in the space charge layer of a semiconductor-fluid or a semiconductormetal interface. Therefore, the lifetimes of photogenerated carriers increased and the possibility was offered to these species to exchange charge with substrates adsorbed on the photocatalyst surface and initiate chemical reactions [20]. Several semiconductors had energies of their bandgap sufficient for catalyzing a wide range of redox reactions. An ideal photocatalyst should be inexpensive, nontoxic, highly photoactive and stable in the conditions in which the pollutant is present. Some well-known photocatalyst materials were TiO2, WO3, SrTiO3 and Fe2O3 and LaCoO3 [21]. The advantage of using semiconductor based materials as photoactive catalysts in the detoxification of pollutants was the complete mineralization into environment friendly products, without generation of waste, which was not possible in the case of any other treatment method [22]. The other advantages included regeneration, reusability and active under easily available UV-visible photo-light. 1.1.2. Definition of photocatalysis: Photocatalysis was a process where a catalyst participates in modifying the rate of a chemical transformation of the reactants without being consumed in the end under light irradiation [23]. In other words, light was a main factor that activates catalyst activity and elevates reaction rate. Chlorophyll of plants is a typical natural photocatalyst. The difference between chlorophyll photocatayst and synthesized one was, usually chlorophyll captures sunlight to turn water and carbon dioxide into oxygen and glucose, but on the contrary photocatalyst created strong oxidation agent and electronic holes to break down the organic matter to carbon dioxide and water in the presence of photocatalyst, light and water [24]. 5