結合分子臨場吸附與電化學剝離法製備高品質石墨烯;Towards the continuous production of high crystallinity graphene via electrochemical exfoliation with molecular in-situ encapsulation

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题名:	結合分子臨場吸附與電化學剝離法製備高品質石墨烯;Towards the continuous production of high crystallinity graphene via electrochemical exfoliation with molecular in-situ encapsulation
作者:	陳嘉軒;Chen,Chia-Hsuan
贡献者:	機械工程學系
关键词:	電化學剝離;石墨烯;拉曼光譜;透明導電薄膜;:Electrochemical exfoliation;Graphene;Raman spectroscopy;Transparent conductive film
日期:	2016-01-25
上传时间:	2016-03-17 20:48:55 (UTC+8)
出版者:	國立中央大學
摘要:	大量生產高品質石墨烯對於現今石墨烯的應用是相當重要的，雖然使用電化學剝離法可以達到量產高品質石墨烯，然而由於過去的電化學法生產的石墨烯產率相當低，尤其長時間電解下，反應發生飽和，產率無法持續。在本研究論文中，我們使用三聚氰胺分子為添加物來改善電剝離石墨烯的產率和品質，研究發現添加定量三聚氰胺時，所剝離出來的石墨烯比沒有添加多出了20.3wt%。這是由於三聚氰胺上的苯環結構和石墨烯上的苯環結構產生了強的π-π鍵作用力，同時三聚氰胺具有親水性，在水相電解液中，克服層間凡德瓦力，因此當電化學剝離時，可促進石墨烯的剝離。此外，研究也發現，石墨烯一旦被脫層後，表面分子吸附，提供了一種臨場包覆的保護作用，避免酸根進一步的氧化石墨烯表面，經由XPS來測出得到的C/O比為~26.17，且由拉曼光譜所量測到的特徵峰D/G比為~0.45，而片層厚度80%的在3層以下，顯示利用此機制可獲得低氧化程度與高結晶性的少層石墨烯片層。本研究也做了應用端的驗證，利用此石墨烯墨水所合成之透明導電薄膜，其片電阻值為13.5KΩ/sq，與傳統製程相較片電阻降低約85%。而將其與聚乙烯醇縮丁醛(Poly(vinyl butyral); 簡稱PVB)高分子做複合材料，所得到的導電率為3.3*10-3S/m。最後，我們利用一連續性的電解設備使用電化學做連續製程可以得到產率高達1.5g/hr，驗證了利用此概念達到連續合成高結晶性石墨烯的效果，對於未來的石墨烯應用將有很大助益。;Large-scale production of uniform and high-quality graphene is required for practical applications of graphene. The electrochemical exfoliation method is considered as a promising approach for the practical production of graphene. However, the relatively low production rate of graphene currently hinders its usage. Here, we demonstrate, for the first time, a rapid and high-yield approach to exfoliate graphite into graphene sheets via an electrochemical method with small molecular additives; where in this approach, the use of melamine additives is able to efficiently exfoliate graphite into high-quality graphene sheets. The exfoliation yield can increased up to 25 wt% with melamine additives compared to electrochemical exfoliation without such additives in the electrolyte. The proposed mechanism for this improvement in the yield is the melamine induced hydrophilic force from the basal plane; this force facilitates exfoliation and provides in-situ protection of the graphene flake surface against further oxidation, leading to high-yield production ofgraphene of larger crystallite size. The residual melamine can be easily washed away by water after collection of the graphene. The exfoliation with molecular additives exhibits higher uniformity(over 80% is graphene of less than 3 layers), lower oxidation density(C/O ratio of 26.17), and low defect level (D/G< 0.45), which are characteristics superior to those of reduced graphene oxide(rGO) or of a previously reported approach of electrochemical exfoliated graphene(EC-graphene). The continuous films obtained by the purified graphene suspension exhibit a sheet resistance of 13.5 kOhm/sq at ~95% transmittance. A graphene-based nanocomposite with PVB exhibits an electrical conductivity of 3.3×10-3 S/m for the graphene loading fraction of 0.46 vol %. Moreover, the melamine functionalized graphene sheets are readily dispersed in the aqueous solution during the exfoliation process, allowing for production of graphene in a continuous process. The continuous process for producing graphene was demonstrated, with a yield rate of 1.5 g/hr. The proposed method can produce high-crystallinity graphene in a fast and high-yield manner, which paves the path towards mass production of high-quality graphene for a variety of applications
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