二硫化鉬奈米材料應用於鋰二氧化碳電池陰極觸媒

Abstract

18世紀工業革命促使人類生活型態之巨變，使人們對於能源之需求日益遽增，然傳統多使用火力發電作為能量來源，於產能過程中不可避免地造成大量之碳排放，致使全球暖化問題迫在眉睫。近年綠色替代能源之相關研究蓬勃發展，舉凡風力能、太陽能與水力能之研究創新與突破，逐漸帶動再生能源革命。產生能源，即須以特定形式將其加以儲存，電池－目前最為廣泛應用之儲能設備，即成為最佳之研究對象。鋰二氧化碳電池(lithium carbon dioxide battery)因具備高能量密度與高比電容量之優點，亦能解決溫室氣體排放之問題，已成為近年極具潛力之儲能裝置。 本研究合成二硫化鉬(molybdenum disulfide)複合奈米碳纖維(carbon nanofibers)與奈米碳管(carbon nanotubes)作為鋰二氧化碳電池觸媒。奈米級碳材具極佳之導電性與熱穩定性，與其高表面積之特性助於儲存放電之碳酸鋰(lithium carbonate)沉積。二硫化鉬具特殊催化性質，助於充電時催化碳酸鋰分解。 本研究藉由X光粉末繞射儀(X-ray diffraction spectroscopy; XRD)、同步輻射X光吸收光譜(X-ray absorption spectroscopy; XAS)與X射線光電子能譜儀(X-ray photoelectron spectroscopy; XPS)鑑定觸媒晶格與價態；以掃描式電子顯微鏡(scanning electron microscope; SEM)與穿透式電子顯微鏡(transmission electron microscopy; TEM)觀察觸媒之形貌；並藉循環伏安法(cyclic voltammetry; CV) 與電化學交流阻抗法(electrochemical impedance spectrum; EIS)探討觸媒電化學活性；再藉拉曼光譜分析儀(Raman analysis spectroscopy; Raman)探討觸媒之二維平面性質；最終藉充放電機測試電池電容量與循環圈數穩定性。經上述檢定，二硫化鉬奈米複合材料具降低鋰二氧化碳電池過電壓之效果，且具極佳循環穩定性。

The industrial revolution in eighteenth-century has caused great change in humans’ life. Human beings’ demand for energy has increased dramatically, while fossil fuel is the common energy resources in the past decades, a large number of carbon emissions are inevitably generated in the process of energy production. Therefore, the serious problem of global warming has emerged imminently. Recent years, the related researches of green alternative energy have flourished. Inspired by the innovation and breakthrough of sustainable energy research, such as wind energy, solar energy, and water energy, the renewable energy revolution is gradually driven. When we generate energy, we must use specific devices to store it. Battery, the widely used energy storage device currently, is the best candidate for energy storage. Lithium carbon dioxide battery with the advantages of high energy density, high specific capacity and the solution to the emission of greenhouse gas nowadays has become a promising energy storage device in the past years. In this study, we synthesized molybdenum disulfide combined with carbon nanofibers or carbon nanotubes as cathode catalysts for lithium carbon dioxide battery. Nano-scaled carbon materials possess excellent conductivity and thermal stability. In addition, the high surface of nanomaterials has contributed to the storage of lithium carbonate which serves as the discharging product in the battery. When charging, the molybdenum disulfide has a catalytic activity to help decomposed lithium carbonate. X-ray diffraction spectroscopy, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy were used to characterize crystal lattice and oxidation state of catalysts. Scanning electron microscope and transmission electron microscopy were used to observe the morphology of catalysts. Following, the cyclic voltammetry and electrochemical impedance spectroscopy were executed to investigate catalytical electrochemistry activity. Furthermore, Raman spectroscopy was implemented to understand the 2D properties of catalysts. In the end, battery capacity and cycle stability were measured by galvanostatic discharge/charge machine. According to the characterization above, molybdenum disulfide with nanofibers materials are capable of decreasing overpotential during discharge and charge and possessing extremely remarkable cycles of stability.