VIETNAM NATIONAL UNIVERSITY-HOCHIMINH CITY HOCHIMINH CITY UNIVERSITY OF TECHNOLOGY -------------------- VAN-PHUONG DO SYNTHESIS OF La1-xSrxCoO3 NANO- PHOTOCATALYSTS USING CARBONACEOUS MICROSPHERES TEMPLATE AND THEIR PHOTOCATALYTIC ACTIVITIES Major of Chemical Engineering Code: 60.75 MASTER THESIS HO CHI MINH CITY, 2015 VIETNAM NATIONAL UNIVERSITY-HOCHIMINH CITY HOCHIMINH CITY UNIVERSITY OF TECHNOLOGY -------------------- VAN-PHUONG DO SYNTHESIS OF La1-xSrxCoO3 NANO- PHOTOCATALYSTS USING CARBONACEOUS MICROSPHERES TEMPLATE AND THEIR PHOTOCATALYTIC ACTIVITIES Major of Chemical Engineering Code: 60.75 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. Huynh Ky Phuong Ha The secondary examiner: Assoc. 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.
Le Thi Kim Phung 2. Huynh Ky Phuong Ha 3. Nguyen Dinh Thanh 4. Nguyen Tuan Anh 5.
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. Le Thi Kim Phung Prof. Phan Thanh Son Nam ĐẠI HỌC QUỐC GIA TP.
HCM CỘNG HÒA XÃ HỘI CHỦ NGHĨA VIỆT NAM TRƯỜNG ĐẠI HỌC BÁCH KHOA 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. 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, 0.8) 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). 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. CÁN BỘ HƯỚNG DẪN CHỦ NHIỆM BỘ MÔN ĐÀO TẠO TS.
Lê Minh Viễn PGS. Huỳnh Kỳ Phương Hạ TRƯỞNG KHOA GS. 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. 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, 0.8) and nanometric photocatalyst La0.4CoO3 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 11.4CoO3 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 La0.4CoO3 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. II TABLE OF CONTENTS ACKNOWLEDGEMENTS. II TABLE OF CONTENTS.
III TABLE FOR ABBREVIATIONS. VI LIST OF FIGURES. VIII LIST OF TABLES. Definition of photocatalysis.
Mechanism of photocatalytic degradation of MB. Mechanism of photocatalytic degradation of CO2. Solid-state reaction. Chemical co-precipitation method.
Sol-gel method. Microwave-assisted method. 16 III CHAPTER 2: LITERATURE REVIEW OF LaCoO3 PHOTOCATALYTIC MATERIAL. 18 CHAPTER 3: MATERIALS AND EXPERIMENTAL METHODS.
The content of research. Materials and equipment. 33 CHAPTER 4: RESULTS AND DISCUSSION. La1-xSrxCoO3 characterization.
Perovskite type La1-xSrxCoO3 photocatalysts synthesized by sol-gel method .4CoO3 photocatalysts fabricated by surface-ion adsorption method using carbonaceous microspheres template. Photocatalytic degradation of MB. Calibrate curve of MB. Perovskite type La1-xSrxCoO3 photocatalysts synthesized by sol-gel method.
Perovskite type La1-xSrxCoO3 photocatalysts synthesized by surface-ion adsorption method. Photocatalytic reduction of CO2. 53 CHAPTER 5: CONCLUSION AND FUTURE WORK. 58 IV LIST OF PUBLICATIONS.
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 Methylene blue VOCs Volatile organic compounds CMs Carbonaceous microspheres LSC28-S850 La0.8CoO3, sol-gel method, 850 oC, 4h LSC46-S850 La0.6CoO3, sol-gel method, 850 oC, 4h LSC64-S850 La0.4CoO3, sol-gel method, 850 oC, 4h LSC82-S850 La0.2CoO3, sol-gel method, 850 oC, 4h LC-S850 LaCoO3, sol-gel method, 850 oC, 4h LSC64-S500 La0.4CoO3, sol-gel method, 500 oC, 4h LSC64-M500 La0.4CoO3, surface-ion adsorption method, 500 oC, 4h LSC64-M550 La0.4CoO3, 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). Schematic diagram of photocatalytic process initiated by photon acting on the semiconductor. Schematic representation of the photocatalytic reduction of CO2 with H2O on the anchored titanium oxide.
Crystal structure of perovskite. Structure formula of methylene blue. Schematic illustration of the synthetic procedure used to obtain La2O3@CMSs. 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.
Photocatalytic decomposition of methylene orange over LaCoO3 catalysts calcined at different temperature. Photocatalytic degradation of malachite green with La1-xBaxCoO3 (x = 0.5) catalyst under: (a) UV light and (b) visible light. Reproducibility tests for the catalytic combustion of 2% CO/1% O2 over Cit3 sample as a function of temperature.5 g sample, 250 ml/min gas volume flowrate. CO catalyst oxidation quartz reactor, inside a heating mantle, with a thermocouple temperature probe, inserted into the reactor over the catalytic bed.
The yield of formic acid and formaldehyde from photoreduction of CO2 on LaCoO3 and C-doped LaCoO3 under three different radiation source. Flowchart of La1-xSrxCoO3 synthesis process by the sol-gel method. Flowchart of carbonaceous microspheres synthesis process. Flowchart of nano perovskite La0.4CoO3 synthesis process.
Experimental setup model for the photocatalytic reduction of CO2. Schematic diagram of FTIR spectroscopy instrument. XRD patterns of La1-xSrxCoO3 (x = 0, 0. XRD patterns of (a) LSC64-S850 and (b) LSC64-S500 powders.
EDX image of LSC64-S850 powder. SEM image of LSC64-S850 powder. UV-vis diffuse absorption spectra of La1-xSrxCoO3 powders. SEM image of carbonaceous microspheres synthesized at 170 oC for 11h.
FTIR spectrum of carbonaceous microspheres. XRD patterns of (a) LSC64-M500 and (b) LSC64-M550. XRD pattern of LaCoO3 product obtained using calcining at 550 oC for 4h. SEM images of LSC64-M500 (left) and LSC64-M550 (right).
EDX image of LSC64-M500. UV-vis diffuse absorption spectra of LSC64-S850 and LSC64-M500 powders. Calibrate curve of methylene blue solution. Degradation of MB (30 mg/L) with different photocatalysts La1-xSrxCoO3 (x = 0, 0.8) under the irradiation of UV light (365 nm).
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). 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.
Experimental conditions for MB adsorption stage. Experimental conditions of MB degradation stage under UV light. Weight% and Atomic% of elements of LSC64-S850 catalyst. Weight% and Atomic% of elements of LSC64-M500 catalyst.
MB lost yield of La1-xSrxCoO3 photocatalysts. MB lost yield of LSC64-S500, LSC64-S850, LSC64-M500 and LSC64- M550. 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.