Scalable Production of Graphene Nanosheets with High Yield and Low Defect and Heteroatom-Doped Graphene Nanosheets by Mechanochemical Exfoliation

• Main Authors: Jia-Liang Liao, 廖家樑
• Other Authors: Wei-Hung Chiang
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/92545604467686933894

碩士 === 國立臺灣科技大學 === 化學工程系 === 105 === Graphene is a two-dimensional carbon nanomaterials with superior electronic, thermal, and mechanical properties and currently explored in advanced electronics, transparent protective coating, energy storage devices and polymer composites. It is highly desirable to economically produce high-quality graphene in industrial quantities to commercially realize its applications; however, no scalable method exists. Mechanochemical approaches to graphene nanosheets synthesis offer the promise of improved yields, new reaction pathways, and greener and more efficient syntheses, making them potential approaches for low cost production of graphene nanosheets. Here we report the scalable production of single- and few-layer graphene nanosheets with low defect densities by an efficient water-assisted mechanochemical exfoliation of graphite in N-methylpyrrolidinone (NMP). The mechanochemical exfoliation could be further improved by applying high speed homogenization and ultrasonication as pretreatments. It is found that the former step homogenized the graphite-solvent solution while the latter provided sufficient energy to weaken the van der Waals interactions and promoted the intercalation of solvent molecules into the graphene sheets within bulk graphite. Significantly, when NMP with water was employed as the cosolvent in the mechanochemical exfoliation, it was found to be possible to produce graphene nanosheets with fewer defects. Detailed materials characterization including transmission electron microscopy, Raman spectroscopy, and UV-Vis absorbance spectroscopy suggest that single- and few-layer graphene nanosheets were successfully prepared with the concentration and yield up to 21.9 mg/mL and 43.8%, respectively. The yield may be further improved by optimizing the process conditions. Our work provides a guide of rational design of a solvent system to improve the yield and stability of the exfoliated materials. Furthermore, the mechanochemical cracking of graphitic C=C bonds generated active carbon species that react directly with melamine to form C-N bonding at the broken edges, leading to edge-nitrogenated graphene nanoplatelets (NGnPs) with superb catalytic performance in both dye-sensitized solar cells and fuel cells to replace conventional Pt-based catalysts for energy conversion. Heteroatom doping can endow carbon nanomaterials with various enhanced optical, structural, and physicochemical properties, making carbon nanomaterials become a promising material in various applications including nano-electronics, catalysis, energy storage, functional composites, and biomedical applications. However, current synthesis methods usually involve complicated vacuum systems, making it difficult to enable industrial-scale production. Consequently, the development of a controllable synthesis of heteroatom-doped carbon nanomaterials at atmospheric pressure will lead to important advances on both scientific studies and innovation applications. Therefore, this study demonstrates a simple ball milling method to produce heteroatom-doped carbon nanomaterial with heteroatoms nitrogen (N), which is under atmospheric pressure.