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Feng Du-PhD Thesis.pdf (4.18 MB)

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Hierarchically Structured Carbon Nanotubes for Energy Conversion and Storage

Du, Feng
http://rave.ohiolink.edu/etdc/view?acc_num=dayton1375459272

Abstract Details

2013, Doctor of Philosophy (Ph.D.), University of Dayton, Materials Engineering.
As the world population continues to increase, large amounts of energy are consumed. Reality pushes us to find new energy or use our current energy more efficiently. Researches on energy conversion and storage have become increasingly important and essential. This grand challenge research has led to a recent focus on nanostructured materials. Carbon nanomaterials such as carbon nanotubes (CNTs) play a critical role in all of these nanotechnology challenges. CNTs have a very large surface area, a high electrochemical accessibility, high electronic conductivity and strong mechanical properties. This combination of properties makes them promising materials for energy device applications, such as FETs, supercapacitors, fuel cells, and lithium batteries. This study focuses on exploring the possibility of using vertically aligned carbon nanotubes (VA-CNTs) as the electrode materials in these energy applications. For the application of electrode materials, electrical conductive, vertically aligned CNTs with controllable length and diameter were synthesized. Several CVD methods for VA-CNT growth have been explored, although the iron / aluminum pre-coated catalyst CVD system was the main focus. A systematic study of several factors, including growth time, temperature, gas ratio, catalyst coating was conducted. The mechanism of VA-CNTs was discussed and a model for VA-CNT length / time was proposed to explain the CNT growth rate. Furthermore, the preferential growth of semiconducting (up to 96 atom% carbon) VA-SWNTs by using a plasma enhanced CVD process combined with fast heating was also explored, and these semiconducting materials have been directly used for making FETs using simple dispersion in organic solvent, without any separation and purification. Also, by inserting electron-accepting nitrogen atoms into the conjugated VA-CNT structure during the growth process, we synthesized vertically aligned nitrogen containing carbon nanotubes (VA-NCNTs). After purification of the metal catalyst, these metal-free VA-NCNTs have shown even better oxidation reduction reaction (ORR) performance than commercially available platinum based electrodes in many aspects, including electrocatalytic activity, long-term operation stability, and tolerance to fuel-molecule crossover. Quantum mechanics calculations and electrochemical experimental results indicate that the charge-deficient carbon atoms around the electron-rich nitrogen atoms improve the ORR reaction and the action of the electrochemical cycling. Finally, by growing vertically aligned carbon nanotubes between graphitic layers in thermally-expanded HOPG, we developed a novel, controlled orientation 3D VA-CNT-graphene architecture, which could allow free transport of electrons and ions. These 3D architectures with a tunable pillar length were demonstrated to be excellent electrode materials for energy related devices. Further, these 3D structures were functionalized with nickel hydroxide by electrodeposition, and the resultant hybrid materials could deliver a high energy density (e.g., ~35 Wh/kg) at a high power density (e.g., ~8 kW/kg), which would significantly outperform many currently available electrode materials.
Daniel Eylon (Committee Chair)
Liming Dai (Committee Member)
146 p.
Energy; Materials Science; Nanoscience
Carbon Nanotubes; Nitrogen Containing; 3D Pillared; Graphene; Energy Conversion; Energy Storage

Recommended Citations

Citations

  • Du, F. (2013). Hierarchically Structured Carbon Nanotubes for Energy Conversion and Storage [Doctoral dissertation, University of Dayton]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1375459272

    APA Style (7th edition)

  • Du, Feng. Hierarchically Structured Carbon Nanotubes for Energy Conversion and Storage. 2013. University of Dayton, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=dayton1375459272.

    MLA Style (8th edition)

  • Du, Feng. "Hierarchically Structured Carbon Nanotubes for Energy Conversion and Storage." Doctoral dissertation, University of Dayton, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1375459272

    Chicago Manual of Style (17th edition)

dayton1375459272
1,149
© 2013, all rights reserved.
This open access ETD is published by University of Dayton and OhioLINK.