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| Title: | 奈米錳/石墨烯複合材料應用於電容去離子技術 |
| Other Titles: | Application of nano manganese/graphene composite for capacitive deionization (CDI) |
| Authors: | 林志穎;Lin, Chih-Ying |
| Contributors: | 淡江大學水資源及環境工程學系碩士班
彭晴玉;Peng, Ching-Yu |
| Keywords: | Capacitive Deionization;Graphene;Manganese;石墨烯;電容去離子;錳 |
| Date: | 2017 |
| Issue Date: | 2018-08-03 15:05:48 (UTC+8) |
| Abstract: | 因人口增加、經濟發展與氣候變遷等因素，造成全球水資源匱乏。地球水資源中，海水佔97%，因此，海水淡化技術成為近年來各國重點開發之技術。電容去離子技術 (capacitive deionization, CDI) 是一種利用電吸附程序去除水中離子的電化學水處理技術，CDI具低成本、低能耗、無二次污染等優點，可應用於去除水中之鹽分。CDI 基本原理是將兩電極間施加電場，使帶電荷之離子吸附於相反電荷之電極表面，形成電雙層，藉以達到去除水子離子之目的。本研究目的為開發新穎電極材料，以應用於電容去離子技術。
電極材料為CDI系統之核心，比電容、導電性、比表面積及濕潤性等，都是良好電極材料之關鍵因素；石墨烯(graphene (rGO))為近年來倍受矚目之導電材料，因其具有高的比表面積、良好導電性及良好的化學惰性，所以適合應用於 CDI 系統。本研究中以X-ray繞射分析、掃描式電子顯微鏡、穿透式電子顯微鏡、比表面積分析儀(BET)、接觸角量測及電化學分析(循環伏安法、計時電位、計時電流、電極阻抗)等方法，探討電極材料表面特徵及電化學特性。
使用改良式Hummer法製備氧化石墨烯(graphene oxide (GO))，並以還原劑Dithionite進行還原GO生成rGO。並添加環境友善之錳金屬，使用Ex-situ、In-situ、Mn@C核殼材料三種方法改質石墨烯；Ex-situ法為使用已還原好之石墨烯加入奈米錳金屬，製成Mn/rGO複合材料；In-situ法則是使用氧化石墨烯於不添加還原劑情況下，利用錳還原氧化石墨烯還原，錳同步被氧化為奈米錳並複合為Mn/rGO複合材料；此外，添加Mn@C核殼顆粒形成Mn@C/rGO複合材料，三種方法皆可提升電極之比電容，比電容與未改質的rGO相比，從原始rGO的 42.19 F/g，三種方法在最佳配比狀況下，分別提升至178.23 F/g、179.64 F/g、107.33 F/g，而比電容的增加主要是因為錳金屬的法拉第虛擬電容(Faradic pseudocapacitance)所貢獻。
將三種複合材料應用於CDI系統，進行鹹水中NaCl之電吸附研究，使用還原劑Dithionite之石墨烯每克可吸附0.22毫克NaCl，而三種改質(Ex-situ、In-situ、Mn@C)分別為4.12 mg/g、1.54 mg/g、2.86 mg/g，吸附量皆大幅提升，而Ex-situ改質吸附量提升最多。
Because of population growth, economic development and climate change, global water resources are scarce. The oceans contain 97 percent of the Earth''s water, so desalination has become a key technology in recent years. Capacitive Deionization (CDI) is a technique for removing ions from water by electrosorption. The advantages of CDI system include low cost, low energy consumption and without secondary pollution.
The basic principle of CDI is that an electric field is applied between two electrodes, so that the charged ions are electro-adsorbed on the electrode with opposite charge.
The purpose of this study is to develop a novel electrode material for CDI system. The key factors for an outstanding electrode material are specific capacitance, specific surface, conductivity and wettability.
Graphene is one of the most popular carbon based material in recent years. Due to its high specific surface area, great electrical conductivity and good chemical inertness, it is a good candidate for electrode material of CDI system.
In this study, X-ray diffraction, scanning electron microscope , transmission electron microscope, surface area analyzer, contact angle analyzer and electrochemical analyzer (cyclic voltammetry, chronopotentiometry, chronoamperometry and electrochemical impedance spectroscopy) to observe the characteristics of electrode material.
Graphene oxide (GO) was prepared by modified Hummer''s method, and then reduced by dithionite to produce graphene (rGO).
The additions of environmental friendly manganese with graphene were synthesized by ex-situ method, in-situ synthesis and mixing with Mn@C core-shell nanoparticles.
Ex-situ method mixed graphene and nano-manganese particles to form Mn/rGO composite.While for in-situ method, the preparation of manganese nanoparticles/graphene composites was conducted with manganese serving as reductant to reduce GO. In the in-situ procedure, manganese is oxidized and GO is reduced to rGO simultaneously. In addition, Mn@C/rGO composites were prepared by the addition of Mn@C core-shell particles to graphene.
These three methods significantly enhance the specific capacitance of the electrode from 42.19 F/g (original rGO) to 178.23 F/g (ex-situ), 179.64 F/g (in-situ), and 107.33 F/g (Mn@C), respectively. The increase in specific capacitance is mainly due to the manganese Faradic pseudocapacitance contribution.
Applying three kinds of composite materials to CDI system, study on the electroadsorption of NaCl in brackish water.
Using of reduced by dithionite to produce graphene electrode presents a electrosorption capacity of 0.22 mg/g NaCl,three methods of MnO2/graphene (Ex-situ, In-situ, Mn@C) composite electrode presents a superior electrosorption capacity respectively 4.12 mg/g, 1.54 mg/g and 2.86 mg/g, the adsorption capacity increased greatly, and the adsorption capacity of Ex-situ was the highest. |
| Appears in Collections: | [水資源及環境工程學系暨研究所] 學位論文
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