Thesis Development of Z-scheme heterojunction Type II photocatalysts for efficient degradation of pollutants under solar light irradiation Graduate School of Yeungnam University Department of Chemical Engineering Major in Chemical Engineering NGUYEN VAN QUANG Advisor: Prof. Jae-Jin Shim August 2021 Ph. Thesis Development of Z-scheme heterojunction Type II photocatalysts for efficient degradation of pollutants under solar light irradiation Advisor: Prof. Jae-Jin Shim Presented as Ph.
Thesis August 2021 Graduate School of Yeungnam University Department of Chemical Engineering Major in Chemical Engineering NGUYEN VAN QUANG Nguyen Van Quang’s Ph. Dissertation is approved Committee member Prof. Moonyong Lee, Ph.D _____________ _____________ Committee member Prof. Jae-Jin Shim, Ph.D _____________ Committee member Prof.
Taeho Yoon, Ph.D Committee member Prof. Jinwoo Lee, Ph.D _____________ Committee member Prof. Dohyung Kang, Ph.D _____________ August 2021 Graduate School of Yeungnam University THƯ VIỆN TRƯỜNG ĐẠI HỌC BÁCH KHOA – ĐẠI HỌC ĐÀ NẴNG. Lưu hành nội bộ Acknowledgments Firstly, I would like to express gratitude from the bottom of my heart to my supervisor Prof.
Jae-Jin Shim for his guidance, sincere advice, and supports during my stay for combined Master and Ph.D program at Nano Energy Materials and Processing lab (formerly, Supercritical Fluids and Nano Processing Lab). I would also like to thank the committee members: Prof. Moonyong Lee, Prof. Taeho Yoon, Prof.
Jinwoo Lee (KAIST), and Prof. Dohyung Kang for useful and valuable recommendation on my dissertation and final defense. Secondly, I would like to give my gratitude to postdocs and research professors in NanoEMAP lab: Dr. Kathik, and Dr.
Debananda for their sharing of knowledge and research experience. I would like to express my thanks to the past and present lab members: Dr. Chinh, Mr Tue, Ms. Jinho, who shared their study experience and helped me in the life in Korea.
I am also grateful to the Graduate School of Yeungnam University, which provided me with full scholarship for my combined Master and Ph.D course, and the BK21+ Program for the financial support during my stay in Yeungnam University. Further, I would like to thank my senior staff from Building Material Division, Faculty of Bridge and Road engineering, and close friends (Mr. Quang Hung, Mr. Minh Hoang, Ms.
Minh Tri, Mr. Van Thanh, Ms. Thi Phuong, Mr.) from Vietnam and (Mr. Van Dung, Mr.
Van Nam, Ms. Vinh Quy) in Korea for their company and encouragement during my stay in Korea. Special thanks as well to Prof. Doan Quang Vinh (Rector of University of Science and Technology-The University of Danang), Dr.
Huynh Phuong Nam (Head of Department of Personal Management-The University of Danang), Dr. Cao Van Lam (Dean of Faculty of Bridge and Road Engineering, University of Science and Technology-The University of Danang) for their unwavering support from Vietnam towards the completion of my doctoral degree. To 사모님, Prof. Shim’s wife, for her best regards to me and great Korean meals.
Lastly, I am very grateful to my lovely family for special care, love, encouragement, and supports. I would like to thank my parents (Dieu Nguyen, Thi Be Nguyen), my siblings (Hung i THƯ VIỆN TRƯỜNG ĐẠI HỌC BÁCH KHOA – ĐẠI HỌC ĐÀ NẴNG. Lưu hành nội bộ Nguyen, Thi Nguyet Nguyen, Thi Nga Nguyen, Son Nguyen), my brothers and sisters-in-law (Phu Trong Nguyen, Day Pham, Thi Nga Hoang, Thi Hang Vo) and all my nephews and nieces. Thank you for beautiful memories with all of you in Korea.
Nguyen Van Quang Yeungnam University Republic of Korea August 2021 THƯ VIỆN TRƯỜNG ĐẠI HỌC BÁCH KHOA – ĐẠI HỌC ĐÀ NẴNG. Lưu hành nội bộ ii THƯ VIỆN TRƯỜNG ĐẠI HỌC BÁCH KHOA – ĐẠI HỌC ĐÀ NẴNG. Lưu hành nội bộ Abstract Recently, the Z-scheme photocatalytic system has attracted more attention in the photocatalyst designs for environmental remediation applications. Compared with conventional designs of the photocatalysts, the Z-scheme-based design has been selected as an ideal solution to improve the photocatalytic activity and stability of the catalysts.
This Z-scheme photocatalytic system not only reduces the recombination of photoinduced electrons and holes but also maintains a prominent redox ability. This dissertation builds up the story of various photocatalytic systems from the simple construction of ZnO/graphene to the Zscheme-based construction among semiconductors (TiO2, C-MoS2, BiPO4, BiOCl, Ag/AgBr, BiOBr, and Bi2O3). For each photocatalytic system, the synthesis method, characterization, and photocatalytic activities of the photocatalysts in the degradation of organic pollutants, such as methylene blue (MB), rhodamine B (RhB), and methyl orange (MO), tetracycline hydrochloride (TCH), hydroxychloroquine (HCQ) in water are presented. In addition, the mechanism of pollutant degradation at each photocatalytic system was also discussed.
iii In Chapter 2, the nanospherical ZnO/rGO composite synthesized by a twostep method showed the high MB and RhB removal efficiencies and good stability under UV light. In Chapter 3, a Z-scheme heterojunction photocatalyst of C-MoS2/TiO2 nanocomposite was prepared by a two-step hydrothermal method (high temperature and high pressure). The Z-scheme photocatalyst exhibited the improvement of photocatalytic activity in the degradation of MB, RhB, and TCH under solar light. In Chapter 4, a facile and rapid microwave-assisted one-step method was used to synthesize the Z-scheme ternary photocatalyst of silk cocoon-like BiPO4 on BiOBr/Bi2O3 nanosheets.
The Z-scheme charge transfer mechanism among three bismuth-based components resulted in a stronger enhancement of RhB degradation under solar light. The photocatalyst also performed good photocatalytic activity towards the TCH, HCQ, and MO pollutants under solar light. Following the same synthesis method as in Chapter 4, the Z-scheme ternary photocatalyst of layer-structured BiOCl/BiOBr/Bi2O3 nanocomposite was prepared and the excellent photocatalytic activity and good stability of the catalyst were demonstrated in the degradation of RhB dye with high dye iv concentration under visible and solar light. Moreover, this Z-scheme photocatalyst also showed good photocatalytic activity for TCH and MO pollutants.
Chapter 6 presents the synthesis of Z-scheme quaternary photocatalyst of Ag/AgBr@BiOBr/Bi2O3 nanocomposite using the same method as described in Chapters 4 and 5. This quaternary photocatalyst is highly efficient in degrading the MO dye with high removal efficiency and excellent stability under visible light. The photocatalyst also showed the good photocatalytic activity for RhB and TCH under different light sources: Light-emitting diode (LED), halogen lamp (from an overhead projector), and simulated solar light. In addition, the rapid microwave-assisted one-step method could be used in the large-scale processes for synthesizing the good Z-scheme photocatalysts for the field of environmental remediation because the method is facile, fast, and controllable.
Table of Contents Acknowledgments. iii Table of Contents. vi List of Figures. v viii List of Schemes.
xvi List of Tables. Solvent-driven morphology-controlled synthesis of highly efficient long-life ZnO/graphene nanocomposite photocatalysts for the practical degradation of organic wastewater under solar light .3 Results and Discussions. Synthesis of (101)-faceted octahedral TiO2 wrapped with MoS2/C as visible light driven Z-scheme photocatalyst for the degradation of organic pollutants .3 Results and Discussions. Facile microwave-assisted synthesis of Z-scheme of silk cocoon-like BiPO4 on BiOBr/Bi2O3 nanosheets for degradation of organic pollutants under solar light .3 Results and Discussions.
Facile microwave-assisted synthesis of Z-scheme photocatalyst of layer-structured BiOCl/BiOBr/Bi2O3 nanocomposite for degradation of organic pollutants under visible light .3 Results and Discussions. Facile microwave-assisted synthesis of sustainable Z-scheme heterojunction photocatalyst of Ag/AgBr nanoparticles on BiOBr/Bi2O3 nanosheets for efficient degradation of organic pollutants under visible light .3 Results and Discussions. Conclusions and Recommendations. 225 vii List of Figures Figure 2.1 XRD pattern of (a) graphite, (b) GO, (c) ZnO seeds/RGO 19 before calcination under Ar gas, (d) RGO, (e) ZnO seeds/RGO after calcination under Ar gas, (f) rZG, (g) dZG, and (h) sZG.
The magnified XRD pattern on the right shows the (100), (002) and (101) crystalline planes of the samples.2 (a) FTIR spectra of GO, ZnO seed/RGO, rZG, dZG, and 21 sZG nanocomposites; (b) Raman spectra of ZnO/RGO nanocomposites and GO and the magnified spectra of the dashed area (ZnO); and (c) G and 2D band peak intensity ratios between ZnO/RGO for the three ZG nanocomposites and GO.3 XPS spectra: (a) survey scan of sZG and GO and (b−d) 25 deconvoluted Zn 2p, O 1s, and C 1s spectra of the sZG sample.4 SEM images of ZnO/RGO samples: (a) ZnO seeds/RGO, (b)27 rZG, (c) dZG, and (d) sZG.5 32 TEM (a1−c1) and HRTEM (a2−c2) images and the corresponding SAED patterns (a3−c3) of ZnO/RGO samples (rZG (a), dZG (b), and sZG (c)) and elemental mapping (d) and EDX spectrum (e) of sZG.6 (a) Nitrogen adsorption-desorption isotherms and (b) pore- 34 size distribution of the three as-prepared ZnO/RGO nanohybrids: rZG, dZG, and sZG.8 Photocatalytic degradation of a 10 mg L−1 MB solution 42 (a) and a 10 mg L−1 RhB solution (b) under UV irradiation in the absence and presence of RGO, sZG, dZG, and rZG (0.1 g L−1); and pseudo-first order kinetics of the photodegradation of MB (c) and RhB (d) under UV irradiation.9 Photocatalytic degradation of (a) 10 mg L−1 MB aqueous 44 solution at various loading of sZG catalyst under UV irradiation, (b) RhB aqueous solution at various initial concentrations at a catalyst loading of 0.1 g L−1 under UV irradiation, and (c) 10 mg L−1 MB aqueous solution in the presence of the sZG and pure ZnO catalysts under UV and solar light irradiation.10 (a) Trapping experiments for sZG (0.1 g L−1) in a 10 mg 47 L−1 RhB dye solution and (b) photocatalytic stability of sZG (0.5 g L−1) in a 10 mg L−1 MB dye solution under UV irradiation, and (c) SEM images of sZG before the first reaction and after 15 photodegradation cycles.1 XRD patterns of commercial P25 (a), K2Ti6O13 (b), spindle-64 like TiO2 (c), CMS (d), and CMST samples (e).2 XPS spectra of the CMST sample: survey spectrum (a) 66 and deconvoluted high-resolution Mo 3d (b), S 2p (c), C 1s (d), Ti 2p (e), and O 1s (f) spectra.3 Raman spectra of CMS (a1−a2) and CMST (b1−b2) 68 samples and the magnified images (a2−b2) of the rectangular dashed areas in a1 and b1.4 SEM images of P25 (a), bulk MoS2 (b), CMS (c), MST 70 (d), CMST (e), spindle-like TiO2 (f), and EDX elemental mapping of CMST (g−m).5 HR-TEM images (a−e) and SAED pattern of72 CMoS2/octahedral-TiO2 (CMST) (f).6 UV-vis diffuse reflectance spectra (a), PL spectra excited 75 at a wavelength λ = 325 nm at room temperature (b), Nyquist plots (EIS response of electrode sample in the dark as well as in the solar light) (c), and the photocurrent response of the samples (commercial P25, CMS, MST, and CMST) under solar light (d).7 Photodegradation of MB (10 mg L−1) under solar light 80 using different samples, 0.2 g L−1 (a), variations of – ln(C/Co) versus irradiation time (b), Effect of pH of 10 mg L−1 MB-dye solution (0.8 Time-dependent UV-vis absorption spectra of 10 mg L−1 82 tetracycline hydrochloride (TCH) in the presence of CMST (a) and photodegradation of TCH under 150 W Xe lamp with different amounts of CMST catalyst (b).9 Kinetic curve of RhB degradation over the CMST catalyst 85 in the presence of different scavengers (a) and photocatalytic stability of CMST in a 10 mg L−1 RhB dye under solar light (b) and TEM images of CMST before and after five cycles (c).1 XRD patterns of samples: BiOBr/Bi2O3 (S0), 100 BiPO4/BiOBr/Bi2O3 (Samples S1-S4) corresponding to 1, 3, 6, and 12 ml of 0.1 M NaH2PO4 solution.3 SEM images of BiPO4/BiOBr/Bi2O3 (sample S3) and its 103 magnified image from rectangular area.5 UV-vis diffuse reflectance spectra (a) and Tauc plots (b) 106 of BiPO4, BiOBr, Bi2O3, and BiPO4/BiOBr/Bi2O3 samples.6 Photodegradation of 10 mg L−1 RhB (catalyst loading of 108 0.5 g L−1) using different samples: BiPO4, BiOBr, So, S1, S2, S3 and S4 represented for the BiPO4/BiOBr/Bi2O3 synthesized using 0, 1, 3, 6 and 12 ml of 0.1 M NaH2PO4 xi solution, respectively (a); rate constants of photodegrdation reaction in the presence of as-prepared samples (b); Effect of catalyst loading (c) and pH (d) on photodegradation of 10 mg L−1 RhB using (sample S3) under solar light.