| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程系 === 103 === Recent theoretical and experimental studies have suggested that heteroatom doped carbon nanomaterials such as carbon nanotubes (CNTs) and graphenes as novel materials with exceptional properties for applications including nanoelectronics, energy storage, fuel cells, and electrochemical sensing. However, current synthesis methods of heteroatom doped carbon nanomaterials 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.
In this study, sulfur doped carbon nanotubes and phosphorus doped carbon nanotubes are both synthesized by a solution-assisted substitution reaction method at atmospheric pressure, whereas solution-assisted substitution reaction method improves the convention substitution reaction method for low heteroatom doping concentration and non-uniform doping distribution. Pristine multiple wall carbon nanotubes (MWCNTs) synthesized using a water-assisted chemical vapor deposition (CVD) are used as starting materials. The heteroatom doped carbon nanotubes are produced by heating the mixture of heteroatom precursor and multiple wall carbon nanotubes under argon atmosphere from 300 to 1000◦C for four hours at atmospheric pressure. Experimental results indicate that the heteroatom concentrations in the carbon nanotubes could be tuned by controlling the reaction temperature, confirmed by the X-ray photoelectron spectroscopy (XPS) and Raman characterizations. Detailed XPS characterization indicates that the heteroatoms are successfully doped into the sp2 carbon lattice, whereas the heteroatom doping concentration of as-produced heteroatom doped carbon nanotubes employed solution-assisted substitution reaction method is higher than heteroatom doped carbon nanotubes employed conventional substitution reaction method. The systematic Raman characterization is performed and shown the ratio of the D- and the G- bands (ID/IG) is increased for the as-produced samples, indicating the defect densities due to the doping process can be controlled in our method. Thin-film electrical conductance characterization measuring by four-point probe method suggests the electrical conductance of the as-prepared heteroatom doped carbon nanotubes are significantly improved by heteroatom doping, making them useful materials for electronics and electrochemical-base applications. It is also noteworthy from a practical point of view that the developed atmospheric pressure synthesis method is amenable to industrial-scale production since it avoids the need for a vacuum system.
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