電化學暨機械剝離之複合方式製備高品質石墨烯片
Abstract
本研究在液相中以複合電化學暨機械剝離之方法，快速剝離出大量之寡層石墨烯，過濾後在氬/氫(90/10)氣氛控制下進行800℃持續2小時的熱處理，獲得高品質的石墨烯片粉末。實驗首先天然石墨粉在離子溶液中進行循環式正極或負極的電化學插層，利用離子與氣體的插層形成膨脹石墨，接著利用高速均質機的旋轉刀頭，進行循環迴旋式之機械攪動給予膨脹石墨剪切力，打斷石墨層間之凡德瓦鍵結造成脫層剝離。當然，在進行機械剝離時，亦可同時進行電化學剝離，讓兩種剝離機制複合作用，以達到快速、高品質石墨烯片製備之目的。預期藉由離子溶液濃度、正負極作用、插層電壓、插層轉速、剝離轉速、剝離電壓及時間等參數控制，可達到高產率、高品質石墨烯片生產之目的。實驗結果顯示，在插層轉速2000 rpm、插層電壓4 V、插層時間1小時、剝離轉速10000 rpm、剝離時間1小時之最佳條件下，所剝離石墨烯片的平均厚度為2.2 nm、平均大小為1~1.5 μm2，藉由波長521 nm之綠光雷射進行拉曼光譜量測，顯示其2D-band和G-band之強度比值為0.93 (I2D/IG = 0.93)、半高寬的值為67.53 (FWHM= 67.53)，故判斷此法所製備之石墨烯片為寡層石墨烯。此外，藉由重量評估結果證明此法寡層石墨烯片的產率高達20 %，為純電化學剝離產率的兩倍以上。本研究也將所剝離之石墨烯片轉移至300 nm SiO2/Si的基板上，透過光學顯微鏡(OM)、掃描式電子顯微鏡(SEM)、穿透式電子顯微鏡(TEM)及原子力顯微鏡(AFM)等儀器，評估石墨烯片的大小、表面形貌、厚度均勻性及晶格品質。本研究已證實複合電化學暨機械剝離的方法，所製備之石墨烯片具有快速、低成本、高品質、單位產量高及不氧化的優勢，適合發展成產業量產技術，而高品質的寡層石墨烯片將適用於導電漿料、透明導電層或超級電容的開發。
In this study, using the liquid phase electrochemical/mechanical hybrid process for exfoliating a lot of few-layer graphene, after heating to 800 ℃ for two hours under argon/hydrogen (90/10) atmosphere controlled, producing high quality graphene sheet powder. First, natural graphite powder for the experimental circulation of the positive electrode or the negative electrode in an electrochemical intercalation ion solution, the use of intercalation ions and gas to form an expanded graphite, and then homogenized using a high speed clarifixator, a rotary-type cyclic mechanical agitation to generate shear force for expanded graphite, interrupted the van der Waals bonding between the graphite layers caused graphene delamination peel. Of course, during the mechanical exfoliation, simultaneously electrochemical exfoliated can be conducted, both of two mechanisms , in order to achieve fast, high-quality preparation of graphene sheets. Expected by the ion concentration in the solution, the positive and negative intercalation effects, intercalation voltage, intercalation speed, exfoliation parameters such as speed control, voltage and time can be achieved in high throughput, high quality graphene sheets purpose of production. The experimental results showed that the optimum conditions for the exfoliation time of 1 hour under the intercalation speed 2000 rpm, intercalation voltage 4 V, 1 hour intercalation speed of 10000 rpm, the average thickness of the graphene sheet is 2.2 nm the average size of 1 ~ 1.5 μm2, by the wavelength of 521 nm green laser Raman spectroscopy measurements show its 2D-band and G-band of the intensity ratio of 0.93 (I2D / IG = 0.93), half-height width is 67.53 (FWHM = 67.53), so the judgment of graphene sheets prepared by this method is few-layer graphene. Further, by evaluation of the weight of the throughput for this method is proved few-layer of graphene sheets reach to 20 wt.%, the throughput more than pure electrochemical method at least 2 times. This study also be exfoliation the graphene sheet transferred to the 300 nm SiO2 / Si substrate through an optical microscope (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM) and other equipment, to evaluated the size of the graphene sheet, the surface morphology, thickness uniformity and quality of the crystal lattice. This study has confirmed that electrochemical/mechanical hybrid method, graphene sheets prepared for rapid, low cost, high quality, high yields and no oxidation of advantages for development into industrial mass production technology, and high-quality few-layer graphene of the conductive layer applied to the transparent conductive layer eventhough in the development of a super capacitor.
In this study, using the liquid phase electrochemical/mechanical hybrid process for exfoliating a lot of few-layer graphene, after heating to 800 ℃ for two hours under argon/hydrogen (90/10) atmosphere controlled, producing high quality graphene sheet powder. First, natural graphite powder for the experimental circulation of the positive electrode or the negative electrode in an electrochemical intercalation ion solution, the use of intercalation ions and gas to form an expanded graphite, and then homogenized using a high speed clarifixator, a rotary-type cyclic mechanical agitation to generate shear force for expanded graphite, interrupted the van der Waals bonding between the graphite layers caused graphene delamination peel. Of course, during the mechanical exfoliation, simultaneously electrochemical exfoliated can be conducted, both of two mechanisms , in order to achieve fast, high-quality preparation of graphene sheets. Expected by the ion concentration in the solution, the positive and negative intercalation effects, intercalation voltage, intercalation speed, exfoliation parameters such as speed control, voltage and time can be achieved in high throughput, high quality graphene sheets purpose of production. The experimental results showed that the optimum conditions for the exfoliation time of 1 hour under the intercalation speed 2000 rpm, intercalation voltage 4 V, 1 hour intercalation speed of 10000 rpm, the average thickness of the graphene sheet is 2.2 nm the average size of 1 ~ 1.5 μm2, by the wavelength of 521 nm green laser Raman spectroscopy measurements show its 2D-band and G-band of the intensity ratio of 0.93 (I2D / IG = 0.93), half-height width is 67.53 (FWHM = 67.53), so the judgment of graphene sheets prepared by this method is few-layer graphene. Further, by evaluation of the weight of the throughput for this method is proved few-layer of graphene sheets reach to 20 wt.%, the throughput more than pure electrochemical method at least 2 times. This study also be exfoliation the graphene sheet transferred to the 300 nm SiO2 / Si substrate through an optical microscope (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM) and other equipment, to evaluated the size of the graphene sheet, the surface morphology, thickness uniformity and quality of the crystal lattice. This study has confirmed that electrochemical/mechanical hybrid method, graphene sheets prepared for rapid, low cost, high quality, high yields and no oxidation of advantages for development into industrial mass production technology, and high-quality few-layer graphene of the conductive layer applied to the transparent conductive layer eventhough in the development of a super capacitor.
Description
Keywords
石墨烯, 電化學剝離, 機械剝離, Graphene, Electrochemisrty exfoliation, Mechanical exfoliation