Enhanced Photodegradation by New Nitrogen Doped Graphene-Metal oxides Based Nanocomposites Titanium dioxide : 질소가 도핑 된 그래핀을 기반으로 하는 광촉매 나노 복합물의 제작 및 응용

다국어 초록 (Multilingual Abstract)

During the past decades, pollution resulting from organic and inorganic contaminants, is threatening the human life. the release of various contaminates that include products of medicine, fertilizer, pesticide, and dye industries into environment causes a tremendous environmental pollution and hinder the quality of life of human beings. are rising exponentially and are recognized as a serious problem in our society. TiO2 has been considered as one of the lest photocatalystic material in various applications that include pollutant removal. TiO2 is relatively non-toxic, less expensive possess, strong oxidatizing power and chemical stability. However, there are two major bottle necks on the use of TiO2 as photocatalyst has a high energy band gap (3.0 ~ 3.2 eV) causing low optical efficiency and a high rate fast for electron-hole recombination. The first drawback requires a high energy ultraviolet ray (≥400 nm) which exists only 4% in the solar ray for photocatalytic application. Other metal oxides and graphene derivatives can be coupled with TiO2 to enhance the photocatalytic activity. In this particular, a new strategy to synthesize nitrogen doped graphene (NG)/photocatalytic metal oxides (PMO) nanocomposite (NC) as an efficient photocatalyst via a facile hydrothermal method. Therefore, NG-PMO-NC were prepared using NG, bismuth (Bi) and titanium (Ti) oxide precursors. the influence of NG and Ti:Bi properties on photocatalytic efficiencies towards the degradation of methylene blue (MB) have been systematically investigated. The as-synthesized NG-PMO-NCs were characterized using X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), field-emission transmission electron microscopy (FE-TEM), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance spectroscopy.

국문 초록 (Abstract)

현재 의약품, 비료, 농약, 염색제의 제조, 산업폐기물 등과 관련된 많은 환경오염을 유발시키는 다양한 화학물질들이 기하급수적으로 늘어나고 있어 심각한 사회 문제로 인식 되고 있다. 이러한 많은 유해 물질들 중에 존재하는 유기물질들은 물에 잘 녹는 물질들이 많이 존재하고 이들은 상·하수, 지하수, 식수 등에서 우리와 밀접한 관계를 가지는 것들이 많아 문제점을 가지고 있어 유기성 유해물질의 제어에 대한 연구는 매우 중요한 연구 분야 중에 한 부분이 되었다. 그 중에서 요즘 가장 활발히 연구가 진행 되었던 것 중에 하나가 광촉매에 대한 연구이다. 광촉매는 광 에너지만으로 다양한 화학물질들을 안전하게 분해 할 뿐만 아니라 광에 대한 부식이나 반응성이 없다. 특히 광촉매 중에 TiO2는 물이나 대기에 있는 여러 가지 유기물질의 완벽한 무기 작용 (Mineralization)에 사용되는 여러 가지 응용분야를 가진 물질로 알려져 있고, 가격이 저렴하고 강력한 산화력과 용매에 침식되지 않는 화학 안정성을 가져 높은 촉매 활성을 가지고 있으며 인체에 무해하기 때문에 현재 많은 주목을 받고 있는 물질이다.
본 연구에서는 가시광과 자외선에서 광촉매 특성이 나타나고 효율성이 뛰어난 광촉매를 제조하기 위해 질소가 포함된 그래핀 (Nitrogen Doped Graphene)을 제조하여 실험을 진행 하였다. 여기에 TiO2와 비스무트 (Bismuth (Bi))를 그래핀 시트 위에 물리적으로 결합을 시켜 광 효율을 극대화 시킨 광촉매를 제조 하였다. 제조된 나노복합물 (Nanocomposite (NC))로 제조 된 광촉매는 유기오염물질 외 표준물질에 하나인 Methylene Blue (MB)를 광분해하는 실험을 UV-vis을 통해 확인 하였고, 광촉매 효율 향상을 확인 하였다. 또한, 제조된 NC의 특성 평가는 XRD, XPS, FE-SEM, TEM, DRS 등을 통해 진행 하였다.

목차 (Table of Contents)

• Contents
• 1. Introduction····································································1
• 2. Theory ·········································································4
• 2.1 Photocatalyst ································································4
• 2.1.1. Titanium dioxide ·······················································4
• 2.1.2. Photocatalytic mechanism ········································5
• 2.2. Graphene ····································································8
• 2.2.1. Doping ··································································9
• 3. Materials and methods ···············································12
• 3.1. Reagents and instrumentations ···································12
• 3.1.1. Reagents ······························································12
• 3.1.2. Characterization ·····················································12
• 3.2. Preparation Procedures ················································13
• 3.2.1 Preparation of NG ·····················································13
• 3.2.2. Preparation of NG-PMO nanocomposites ·······················14
• 3.2.3. Preparation of few comparison materials························16
• 3.3. Photodegradation experiment ··········································17
• 4. Results and Discussion ··············································18
• 4.1. Characterization··························································18
• 4.1.1. Morphology ··························································18
• 4.1.1.1. FE-SEM analysis ···············································18
• 4.1.1.2. FE-TEM analysis ················································20
• 4.1.2 Microstructural characteristics ································23
• 4.1.2.1. XRD ································································23
• 4.2. Photocatalysis of MB · ···············································26
• 4.3. Photodegradation mechanism ········································30
• 5. Conclusion ································································32
• 6. Reference ····································································34
• 7. Abstract ·······································································39