Preparation And Structural Properties Of Seaweed-based Multi-metal Carbon Fiber Raw Materials

Polysaccharides are easily available in nature and several functional hydrogels may be obtained through physical and chemical modification of polysaccharides. Alginic acid is a natural polysaccharide obtained from brown seaweeds which has been widely used in bio-applications including tissue engineering and drug delivery in the form of alginate hydrogels, due to its excellent biocompatibility, biodegradability and nontoxicity. Sodium alginate (SA) is naturally derived linear copolymer of α-l-guluronic acid (G) units and1,4-linked β-d-mannuronic acid (M) in various composition and sequence.Electro spinning is a recently explored effective and simple fabrication technique for producing nano to microscale fibers and the electrospun mats consist of ultra-fine fibers with high specific surface area and high aspect ratio. Alginate is a water-soluble polymer and forms gel in the presence of certain bivalent cation such as Ca+through ion exchange. We fabricated a new kind of nanofibers which combined sodium alginate with carbon nanotubes(SA-CNTs-NF). Through the measurements of scanning electron microscope, transmission electron microscope, X-ray diffraction analysis, it turned out that the average diameter of the sodium alginate nanofibers with carbon nanotubes was196nm and the carbon nanotubes showed a good dispersion in the nanofibers. Besides, we found that the thermostability of sodium alginate nanofibers was improved by the addition of carbon nanotubes. Then the SA-CNTs-NF were immersed in CoCl2(0.5mol/L) alcohol solution to form the CACNTs-NF, the obtained CACNTs-NF were placed in a tube furnace and heated in ammonia to form the ORR catalysts(N-CANTs-NF). The resulting N-CACNT-NF catalysts showed perfect ORR performance, which can was comparable with Pt/C in reaction current and electrons transferred per molecule of O2. Moreover, N-CACNT-NF catalysts showed a better durability and methanol tolerance ability in comparison to Pt/C.Lithium-ion batteries are regarded as the most promising powers source in the21st century for the wide application range from microbatteries for telephones to power sources for electrical vehicles. Search for a new kind of electrode material with large capacity and long cycle life is a key for the development of high performance lithium-ion batteries. In view of the low capacity of graphite-based materials(theoretical capacity:372mAh/g), which are used extensively in currently commercialized lithium-ion batteries, it is urgent to develop new anode materials with larger capacity and longer cycle life. New type of anode materials was prepared by methods of thermal pyrolysis and hydrothermal, the electrochemical performance was investigated in this thesis. The obtained composite shows large capacity(659mAh/g)and good cycle stability.