臺灣博碩士論文加值系統

本研究為了提升燃料電池之效率以及耐久性，開發了取代碳載體的材料，以提升觸媒活性及耐久性，並且由於活性提升，鉑的使用量得以減少；耐久性的提升，使燃料電池每單位時間的運作成本更可以進一步減少。
本研究的第一部分為：“調整金屬載體相互作用力以提升鉑奈米觸媒於二氧化鈦載體上的活性以及穩定性”。本研究開發了新穎的觸媒處理程序，經由增強金屬載體強相互作用力（strong metal-support interaction, SMSI），而得以大幅提升觸媒活性以及穩定性。此外，首次利用電化學方法作為高效率的表面覆蓋檢測工具，並提供了第一個低溫觸發SMSI的直接證據（200˚C，低於文獻上的500˚C）。
研究的第二部分為：“負載於雙掺雜二氧化鈦載體上的白金作為高活性及高耐久性的氧氣還原反應催化劑”。以鎢或鈮作為陽離子，氮作為陰離子，合成雙摻雜二氧化鈦，負載其上的鉑奈米粒子展現了更好的觸媒活性以及穩定性。並首次結合X射線吸收光譜（X-ray absorption spectroscopy, XAS）及密度泛函理論（density function theory, DFT）以解釋材料表面缺陷如何影響鉑與二氧化鈦載體之間的相互作用，並改變所得到的觸媒性質。

In order to make fuel cell technology competitive with other green energy resources, the activity and durability must be enhanced, and the cost of fuel cell must be reduced. To achieve that target, improve the nature of platinum or replace the carbon support can enhance both activity and durability of the catalyst, the use of platinum on fuel cells can be reduced due to the enhancement of its catalytic activity, and the increased durability is also expected to has further reduced the operation cost of the novel catalyst per running hour.
Therefore, our researches focus on enhancing catalyst activity and durability on oxygen reduction reaction catalyst. The first part of this work is “Tuning metal support interactions enhances the activity and durability of TiO2-supported Pt nanocatalysts”. In this research, strong metal-support interaction (SMSI) in TiO2-supported Pt can be induced at 200˚C by H2 reduction, without high temperature treatment. Moreover, electrochemical methods (methanol oxidation reaction and cyclic voltammetry) are first reported ever to be effective characterization tools for the coverage state caused by SMSI. In addition, the SMSI has also been confirmed by X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and Transmission Electron Microscopy. It is found that the encapsulation of TiOx species on the surface Pt clusters was induced and modified by thermal reduction and fluoric acid treatment. The catalytic activity and durability of the TiO2-supported Pt nanocatalysts are strongly dependent of the state of SMSI. The proposed SMSI-tunable approach to enhance the oxygen reduction reaction (ORR) activity and stability is also proved applicable to Pt/Ti0.9Nb0.1O2 nanocatalysts. We believe that the reported approach paves the way for manipulating the activity and stability of other TiO2-supported metal nanocatalysts. Furthermore, the suggested electrochemical methods offer facile and effective ways to test the presence of coverage state before combining with other physical analysis.
The second part of this work is “Platinum loaded on dual-doped TiO2 as an active and durable oxygen reduction reaction catalyst”. In this research, dual-doped TiO2 was successfully synthesized by using tungsten or niobium as the cation and nitrogen as the anion and, as compared with single-doped TiO2, provided a higher electron conductivity and improved physical properties. Platinum nanoparticles loaded on these materials showed better electrochemical performance, and the Pt/Ti0.9Nb0.1NxOy and Pt/Ti0.8W0.2NxOy catalysts were 2.6-3.7 times more active than the Pt/Ti0.9Nb0.1Oy and Pt/Ti0.8W0.2Oy catalysts without nitrogen doping. Additionally, there was an activity loss of 22.9%, as compared with 81% in Pt/C after 30000 CV cycles, a value exceeding the US Department of Energy (DOE) stability target. Dual doping not only enhances the electron conductivity but also changes the electronic state of Pt on the support materials, thus allowing for more active and stable catalysts. Both X-ray absorption spectroscopy (XAS) and density functional theory (DFT) studies were undertaken to demonstrate how oxygen vacancies formation affects the interactions between Pt and the single- or dual-doped TiO2 supports and manipulates the physical and chemical properties of the resulting catalysts. Thus, these catalytic supports are strong candidates for proton exchange membrane fuel cell applications.

摘要 I
Abstract III
Acknowledgement V
Table of Contents VII
List of tables X
List of schemes XII
List of figures XIII
List of abbreviations XXI
Chapter 1 Introduction 1
1.1 Overview about fuel cell technology 1
1.1.1 Proton exchange membrane fuel cells 4
1.1.2 Challenge of proton exchange membrane fuel cells 7
1.2 Catalyst of oxygen reduction reaction 12
1.3 Catalyst support for oxygen reduction reaction 12
1.3.1 Strong metal support interaction between catalyst and support 13
1.3.2 Conductivity issue of metal oxide supports 15
1.4 Motivation and objective of the research 18
Chapter 2 Material and Methods 19
2.1 Materials 19
2.2 Methods 19
2.2.1 Brunauer-Emmett-Teller (BET) surface area 19
2.2.2 Electronic conductivity 19
2.2.3 X-ray diffraction (XRD) measurements 19
2.2.4 Raman spectra 20
2.2.5 X-ray photoelectron spectroscopy (XPS) measurement 20
2.2.6 X-ray absorption spectroscopy (XAS) measurement 21
2.2.7 Energy dispersive X-ray microanalyzer (EDX) 21
2.2.8 Transmission Electron Microscopy (TEM) and High-resolution Transmission Electron Microscopy (HRTEM) 21
2.2.9 Electrochemical Measurements 22
2.2.10 Computational study 23
2.3 Experiment section 23
2.3.1 Synthesis of Pt/TiO2 catalyst 23
2.3.2 Hydrogen treatment 24
2.3.3 Hydrofluoric acid treatment 25
2.3.4 Synthesis of Pt/Ti0.9Nb0.1O2 catalyst 26
2.3.5 Synthesis of W-doped TiO2 nanoparticle supports 28
2.3.6 Synthesis of dual-doped Ti0.8W0.2NxOy and Ti0.9Nb0.1NxOy nanoparticle supports 30
2.3.7 Pt loading on dual-doped TiO2 supports 31
Chapter 3 Tuning Metal Support Interactions Enhances the Activity and Durability of TiO2-supported Pt Nanocatalysts 35
3.1 Introduction 35
3.2 Results and discussions 37
3.2.1 Characterization of Pt/TiO2 and Pt/TiO2-HT catalysts 37
3.2.2 Electrochemical properties of Pt/TiO2, Pt/TiO2-HT, and Pt/TiO2-HFT catalysts 43
3.2.3 XAS measurement of Pt/TiO2, Pt/TiO2-HT, and Pt/TiO2-HFT catalysts 48
3.2.4 Stability test of Pt/TiO2, and Pt/TiO2-HFT catalysts 51
3.2.5 HFT treatment for Pt/TiNbO2 53
3.3 Summary 57
Chapter 4 Platinum Loaded on Dual-Doped TiO2 as an Active and Durable Oxygen Reduction Reaction Catalyst 59
4.1 Introduction 59
4.2 Results and discussion 63
4.2.1 Optimization of W-doped TiO2 63
4.2.2 Characterization of Ti0.8W0.2NxOy and Ti0.9Nb0.1NxOy supports 71
4.2.3 Electrochemical properties of Pt/Ti0.8W0.2NxOy and Pt/Ti0.9Nb0.1NxOy catalysts 76
4.2.4 XAS measurement and DFT study 82
4.3 Summary 94
Chapter 5 Conclusions and Perspectives 97
Supporting Information 99
References 131
Curriculum Vitae 143
List of publications 144
List of conferences/workshops 145

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