臺灣博碩士論文加值系統

The purpose of this study is to develop a new green process for production of H2O2 through the direct synthesis route, of which the hydrogen and oxygen contacts each other during the reaction. An electrochemical approach with the rotating ring disk electrode (RRDE) had been systematically explored and developed accordingly to measure the produced H2O2. Two different methods – co-reduction and successive reduction prepared in the microwave were adopted to prepare bimetallic Pd-Au/C nanocatalysts. The relationship between the structure of prepared nanocatalysts and their catalytic activity in the direct synthesis process were investigated. As synthesized bimetallic Pd-Au/C were characterized by ICP-AES, XRD, SEM, TEM, and XAS for better understanding in the catalytic activity of direct synthesis of H2O2.
The approach in the electrochemical to measure H2O2 produced from direct synthesis has been successfully done with the detection method 2, where the catalyst is dispersed homogenously in the solution. The calibration curve of the different concentration of H2O2 is made in the parameter of 0.891 V (vs Ag/AgCl) and with the scan rate 50 mV/s. The optimum loading of samples prepared by co reduction was observed in CR Pd3%-Au2%/C with the productivity of H2O2 is 65.8 mol.kgcat-1h-1. This productivity is higher than the other prepared catalysts, such as monometallic Pd0%-Au5% & Pd5%-Au0% and bimetallic SR Pd-Au/C that is prepared by successive reduction. The higher or the lower productivity of one sample to another was explained by the parameter of the particle size, the structure of the bimetallic Pd-Au/C, the selective crystalline plane, and the role of palladium and gold. The smaller the particle size tends to Pd rich, while the larger one tends to Au rich. The smaller particle size yielded in the high surface area, thus the productivity increases. However, if the particle size is too small, the active site or selective crystalline plane may be slightly appeared (as can be seen in SR Pd-Au/C), thus the productivity decreases.
From XAS analysis, the structure CR Pd-Au/C is Au rich in core and Pd rich in shell. The structure of SR PdAu at some part of catalyst is Au rich in core and Pd rich in shell, while at the other part, the structure is Pd in core and Au in shell. The Q value of SR PdAu (0.638) is higher than that of CR PdAu (0.605), which indicates that the existence of Au atoms in the shell of SR PdAu is more than that of CR PdAu. The difference in their structure is one reason why the H2O2 productivity of CR PdAu is higher than SR PdAu. The role of Pd is to provide the surface area for the selective oxidation of hydrogen and the role of Au is to provide inactive site for the reaction of decomposition and hydrogenation of H2O2.

The purpose of this study is to develop a new green process for production of H2O2 through the direct synthesis route, of which the hydrogen and oxygen contacts each other during the reaction. An electrochemical approach with the rotating ring disk electrode (RRDE) had been systematically explored and developed accordingly to measure the produced H2O2. Two different methods – co-reduction and successive reduction prepared in the microwave were adopted to prepare bimetallic Pd-Au/C nanocatalysts. The relationship between the structure of prepared nanocatalysts and their catalytic activity in the direct synthesis process were investigated. As synthesized bimetallic Pd-Au/C were characterized by ICP-AES, XRD, SEM, TEM, and XAS for better understanding in the catalytic activity of direct synthesis of H2O2.
The approach in the electrochemical to measure H2O2 produced from direct synthesis has been successfully done with the detection method 2, where the catalyst is dispersed homogenously in the solution. The calibration curve of the different concentration of H2O2 is made in the parameter of 0.891 V (vs Ag/AgCl) and with the scan rate 50 mV/s. The optimum loading of samples prepared by co reduction was observed in CR Pd3%-Au2%/C with the productivity of H2O2 is 65.8 mol.kgcat-1h-1. This productivity is higher than the other prepared catalysts, such as monometallic Pd0%-Au5% & Pd5%-Au0% and bimetallic SR Pd-Au/C that is prepared by successive reduction. The higher or the lower productivity of one sample to another was explained by the parameter of the particle size, the structure of the bimetallic Pd-Au/C, the selective crystalline plane, and the role of palladium and gold. The smaller the particle size tends to Pd rich, while the larger one tends to Au rich. The smaller particle size yielded in the high surface area, thus the productivity increases. However, if the particle size is too small, the active site or selective crystalline plane may be slightly appeared (as can be seen in SR Pd-Au/C), thus the productivity decreases.
From XAS analysis, the structure CR Pd-Au/C is Au rich in core and Pd rich in shell. The structure of SR PdAu at some part of catalyst is Au rich in core and Pd rich in shell, while at the other part, the structure is Pd in core and Au in shell. The Q value of SR PdAu (0.638) is higher than that of CR PdAu (0.605), which indicates that the existence of Au atoms in the shell of SR PdAu is more than that of CR PdAu. The difference in their structure is one reason why the H2O2 productivity of CR PdAu is higher than SR PdAu. The role of Pd is to provide the surface area for the selective oxidation of hydrogen and the role of Au is to provide inactive site for the reaction of decomposition and hydrogenation of H2O2.

Abstract ii
Acknowledgment iv
List of Figures ix
List of Table xvi
CHAPTER I. INTRODUCTION 1
1.1. General Aspects and Application of Hydrogen Peroxide 1
1.2. The Production of H2O2 3
1.3. Direct Synthesis of H2O2 6
1.4 Drawback in the Catalytic Direct Synthesis of H2O2 8
CHAPTER II. LITERATURE REVIEW & OBJECTIVE 10
2.1 Catalysts used in the Direct Synthesis of H2O2 from H2 and O2 10
2.1.1 Bimetallic Alloy Pd-Au/C Nanoparticles 14
2.1.2 Carbon Support of Pd-Au Nanoparticles 17
2.1.3 Pretreatment to Functionalize the Carbon Support (Carbon Black) 19
2.2 Synthesis of Alloy & Core-Shell Bimetallic Pd-Au/C Nanoparticle 20
2.2.1 Alloy & Core-Shell Bimetallic Nanoparticle 20
2.2.2 Co & Successive Reduction 22
2.3 Electrochemical Measurement for H2O2 Detection with RRDE 24
2.3.1 Collection Efficiency of RRDE 28
2.3.2 Electrochemical Measurement 29
2.4 Research Question 34
2.5 Research Objectives 35
CHAPTER III. EXPERIMENTAL PROCEDURE 36
3.1 Research Mapping 36
3.2 Experiment Materials & Equipment 36
3.3 Preparation of Bimetallic Catalyst Pd-Au/C 38
3.3.1 Pretreatment of Carbon Black 41
3.3.2 Metal Loading with Co-Reduction (CR) in Oil Bath 41
3.3.3 Metal Loading with Co-Reduction (CR) in Microwave 42
3.3.4 Metal Loading with Successive Reduction (SR) in Oil Bath 43
3.3.5 Metal Loading with Successive Reduction (SR) in Microwave 44
3.4 Characterization of Catalyst 46
3.4.1 Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) 46
3.4.2 X-Ray Diffraction (XRD) 48
3.4.3 Transmission Electron Microscopy (TEM) 50
3.4.4 Scanning Electron Microscope (SEM) 51
3.4.5 X-ray Absorption Spectroscopy (XAS) 52
3.5 Electrochemical Detection of Produced H2O2 from The Direct Synthesis 57
3.5.1 Detection Method 1 59
3.5.2 Detection Method 2 62
CHAPTER IV. RESULTS AND DISCUSSION 65
4.1 Catalyst Characterization 65
4.1.1 Bulk Properties 65
4.1.2 Surface Properties 79
4.1.3 Structural Model and Atomic Distribution 87
4.2. Electrochemical Measurement 98
4.2.1 Measurement for the best potential 98
4.2.2 H2O2 detection 112
4.3 Comparison Study in the Direct Synthesis of H2O2 123
4.3.1 Comparison between Monometallic and Bimetallic CR Pd-Au/C 123
4.3.2 Comparison between Monometallic and Bimetallic SR Pd-Au/C 126
4.3.3 Comparison between Bimetallic CR Pd-Au/C and SR Pd-Au/C 128
4.3.4 Comparison in The Electrochemical and Conventional System 130
CHAPTER V. CONCLUSIONS 132
BIBLIOGRAPHY 136

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