Tổng hợp và nghiên cứu khả năng ứng dụng của hạt nano vàng phân bố trên vật liệu polyme carbon nitride

HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY MASTER THESIS Synthesis and Application of PolymericCarbon Nitride decorated with Gold Nanoparticles GIAP VAN HUNG Hung.GV202683M@sis.hust.edu.vn Master of Science in Chemistry Supervisor 1: Institute: Dr Nguyen Thi Tuyet Mai Chemical Engineering Institute Signature Supervisor 2: Dr Norbert Steinfeldt Signature Institute: Leibniz Institute for Catalysis (LIKAT) HANOI, OCTOBER 2022 DECLARATION OF INDEPENDENCE I hereby declare that I have prepared this thesis independently and under the guidance of my supervisor, without using any support and resources other than the RoHan Project funded by the German Academic Exchange Service (DAAD, No 57315854) and the Federal Ministry for Economic Cooperation and Development (BMZ) inside the framework "SDG Bilateral Graduate school programme Hung Giap Van ACKNOWLEDGEMENTS First, I would like to express my deepest gratitude to my co-supervisors Dr Norbert Steinfeldt (LIKAT) and Dr Nguyen Thi Tuyet Mai (HUST), for his help and support throughout my thesis work Without them supervision, I would not have been able to complete my thesis Special thanks to the Department of Physical Chemistry, Institute of Chemical Engineering, Hanoi University of Science and Technology together with the research group of Prof Jennifer Stunk at Leibniz Institute of Catalysis (LIKAT Rostock) created favorable conditions for me to study, research and completed this thesis Finally, I would like to thank my family, friends, and relatives has always accompanied, encouraged, and shared with me They are a great source of motivation for me to continue my research path ABSTRACT Photocatalytic hydrogen generation is increasingly perceived as a potential alternative to traditional hydrogen production method [1] Polymeric carbon nitride (p-C3N4) has been considered as a promising photocatalyst candidate due to its low cost, chemical stability, and visible light reactivity However, the performance of pure p-C3N4 is limited due to the rapid recombination of photoinduced electron-hole pairs Therefore, a lot of methods were explored to improve the activity of p-C3N4 In this work, p-C3N4 was prepared in different atmospheres, treated with H2O2 or ultrasound, and then investigated with Au deposition to optimize its photocatalytic performance Before testing in hydrogen evolution reaction (HER) with triethanolamine (TEOA) as sacrificial agent, the materials were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (FTIR), UV-vis diffuse reflectance spectroscopy (DRS), thermal gravity analysis (TGA), elemental analysis (EA), and photoluminescence spectroscopy (PL) The synthesized materials showed improved charge separation efficiency and H evolution performance The highly-improved performance is ascribed to the efficient transfer of photogenerated electrons among molecule p-C3N4 and Au, which is supported by photoluminescence spectra and transient photocurrent responses TABLE OF CONTENTS ACKNOWLEDGEMENTS ABSTRACT TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES LIST OF ABBREVIATIONS 10 CHAPTER INTRODUCTION 11 1.1 Background 11 1.2 Objectives and outline of the thesis 11 1.2.1 Thesis outline 11 1.2.2 Thesis Objectives 12 CHAPTER LITERATURE REVIEW 13 2.1 Introduction 13 2.2 Graphitic Carbon Nitride (p-C3N4) 14 2.2.1 History 14 2.2.2 Synthesis of p-C3N4 15 2.2.3 Physical and Chemistry properties 21 2.2.4 Modifications 22 2.2.5 p-C3N4 based nanocomposites 25 2.2.6 Trends of photocatalytic development of p-C3N4 27 2.3 Plasmonic Photocatalysis 28 2.3.1 Fundamentals 29 2.3.2 Surface plasmon benefits for photocatalysis 30 2.3.3 Metal nanoparticle/semiconductor junction 32 2.3.4 Gold nanoparticles based on p-C3N4 33 CHAPTER p-C3N4 - SYNTHESIS, CHARACTERIZATION, AND APPLICATION 34 3.1 Experimental 34 3.1.1 Preparation of p-C3N4 34 3.1.2 Post-treatment of p-C3N4 35 3.1.3 Material characterization 36 3.1.4 Photocatalytic -HER reaction 37 3.1.5 Electrochemical characterization 38 3.2 Results and Discussion 38 3.2.1 Structural and thermal properties 38 3.2.2 Optical and electrochemical properties 47 3.2.3 Evaluation of photocatalytic activity toward H2 evolution under white light irradiation 50 CHAPTER Au/p-C3N4 COMPOSITES – SYNTHESIS, CHARACTERIZATION, AND APPLICATION 52 4.1 Experimental 52 4.1.2 Material characterization 54 4.1.3 Photocatalytic and electrochemical measurement .54 4.2 Results and Discussion 55 4.2.1 Effect of the p-C3N4 support 55 4.2.2 Effect of Au loading 61 4.2.3 Effect of Au deposition method 66 4.2.4 Possible photocatalytic mechanism 71 CHAPTER GENERAL CONCLUSIONS AND OUTLOOK 73 5.1 General conclusions 73 5.2 Outlook 73 REFERENCES 75 LIST OF TABLES Table Position of the (002) reflection of p-C3N4 support .39 Table Summary of characteristic parameters determined based on N adsorptiondesorption isotherms of different p-C3N4 samples 42 Table Near surface composition of various p-C3N4 heterostructures .45 Table Atomic ratio of C, H, N of various p-C3N4 obtained by elemental analysis 46 Table Band gap values of various p-C3N4 calculated from Tauc's method 48 Table Position of p-C3N4 (002) reflection and crystallite size of Au nanoparticles of wt.% Au/p-C3N4 samples 56 Table Table of band gap energy of wt.% Au/p-C3N4 calculated from Tauc's method 58 Table Crystallite size, nano size of different wt.% Au based on p-C 3N4 (air) 62 Table Crystallite size and band gap of Au/p-C3N4 synthesized by chemical reduction method 68 LIST OF FIGURES Figure Schematic diagram of the synthesis of p-C3N4 from the thermal polymerization of melamine, cyanamide, dicyandiamide, urea and thiourea [46] 16 Figure 2 Postulated Condensation of Melamine [63] 17 Figure Schematic of self-modification to promote oriented vacancies [78] 19 Figure Using NH3 atmosphere in the synthesis of p-C3N4 [79] 20 Figure a) The pyrolysis time-layer thickness of p-C3N4 [84] b) Synthesis pathway of structurally distorted p-C3N4 nanosheets [87] 21 Figure Scheme of monolayer (a) crystalline and (b) amorphous monolayer of graphite carbon nitride [89] 22 Figure a) The “hard” template approach combines the sol-gel/thermal condensation method [112] b) Different morphologies can be obtained by the “Soft” and “Hard” slide approaches based on p-C3N4 [97] 24 Figure Schematic representation of the charge pairs in p-C 3N4 is shown with decay lines, where A represents the electron acceptor while D is the donor[46] 27 Figure Typical bandgap energy values of semiconductor photocatalysts and redox potentials of processes including H2O separation, CO2 reduction and pollutant decomposition (reaction carried out with pH = 7) [46] 28 Figure 10 Schematic diagram of plasmon oscillations after application of an electric field, and electron cloud formation [145] 30 Figure 11 Scheme of the electromagnetic field intensification on M NP [146] 31 Figure 12 Mechanism of hot electron injection from metal/plasmonic nanoparticles into the semiconductor conduction band [146] 32 Figure Schematic overview about process synthesis of pure p-C 3N4 34 Figure The crucible used in the synthesis of p-C3N4 34 Figure 3 Experimental system treatment p-C3N4 by H2O2 solution (left), the pC3N4 mixture after treatment by H2O2 (right) 35 Figure Treatment p-C3N4 using the BANDELIN SONOPULS HD 2070 ultrasonic transducer system 36 Figure Scheme of the experimental set-up used for study of HER reaction with p-C3N4 catalysts under irradiation with white light 37 Figure XRD patterns of various p-C3N4 samples 39 Figure ATR-IR spectra of all various p-C3N4 40 Figure N2 adsorption-desorption isotherms and corresponding pore size distribution curves (inset) of various p-C3N4 heterostructures 41 Figure The fully survey spectra of XPS spectra for various p-C3N4 heterostructures 42 Figure 10 XPS spectra of C1s, N1s, O1s of all samples .44 Figure 11 TGA-DSC analysis of p-C3N4 support 46 Figure 12 UV-vis DRS spectrum of various p-C3N4 samples .47 Figure 13 PL spectra of various p-C3N4 49 Figure 14.a) Transient photocurrent responses and b) EIS of various p-C3N4 under visible light irradiation 50 Figure 15 Temporal H2 evolution of p-C3N4 samples synthesized under (a) air (300 W Xenon lamp) or (b) Ar atmosphere (1000 W Xenon lamp) after in-situ Au deposition at irradiation with white light (Au amount wt.% ) 51 Figure Schematic illustration of synthetic Au/p-C3N4 by photodeposition method 52 Figure Schematic synthesis of Au/p-C3N4 synthesis by chemical reduction method, using NaBH4 reducing agent 53 Figure Schematic synthesis of Au/p-C3N4 synthesis by chemical reduction method, using NaBH4 reducing agent with surfactant: sodium citrate, PVP 54 Figure 4 LED arrays irradiating visible light (24 V, 1.12 A, 24 W) .55 Figure XRD patterns of synthesized Au/p-C3N4 composites .56 Figure (a) ATR-IR spectra and (b) UV-vis DRS spectra of the different 2wt.% Au/p-C3N4 57 Figure PL spectra of wt.% Au/p-C3N4 59 Figure Transient photocurrent (a) and EIS (b) of Au/p-C 3N4 under visible light irradiation 60 Figure Time course of H2 evolution of Au/p-C3N4 (a) under white and (b) visible light irradiation 60 Figure 10 XRD patterns of Au/p-C3N4 (air) with different wt.% Au 62 Figure 11 SEM images of (a) 2wt.% Au and (b) wt % Au based on p-C3N4 (air) 63 Figure 12 ATR-IR spectra of with different wt.% Au based on p-C 3N4 (air) 64 Figure 13 (a) UV-vis spectra and (b) PL spectra of different wt.% Au based on p-C3N4 (air) 65 Figure 14 Time course of H2 evolution of Au/p-C3N4 (air) with different wt.% Au under white light 66 Figure 15 Characterizations (a) XRD, (b) ATR-IR, (c) PL and (d) UV-vis DRS of different methods of Au/p-C3N4 synthesis 67 Figure 16 SEM images of Au/p-C3N4 synthesized by chemical reduction using (a) NaBH4 in dark, (b) NaBH4 + Sodium citrate and (c) NaBH4 + PVP .69 Figure 17 XPS spectra of various p-C3N4 and Au/p-C3N4: (a) Fully scanned spectra of various p-C3N4 compare with Au/p-C3N4, (b) C 1s, (c) N 1s, (d) O 1s and (e) Au 4f 70 Figure 18 Time course of H2 evolution of Au/p-C3N4 synthesized samples (by different methods) under white light 71 Figure 19 Schematic illustration of the mechanism H2 evolution reaction by Au/p-C3N4 composite from water in the presence of TEOA .72 LIST OF ABBREVIATIONS Abbreviations AuNPs Meaningful Gold nanoparticles CB Conductive Band CVD Chemical vapor deposition EIS Electrochemical impedance spectroscopy GC Gas chromatography HAuCl4 Chloroauric acid HER Hydrogen Evolution Reaction LSPR Localized surface plasmon resonance M Metal M NP Metal Nano Particles MOFs Metal Organic Frameworks NaBH4 Sodium borohydride p-C3N4 Graphitic carbon Nitride PVD Physical vapor deposition PVP Polyvinylpyrrolidone SC Semiconductor TEOA Triethanolamine VB Valence band 10