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Model Development for the Evaluation of Hydrogen Storage Capacity in Hybrid Nanostructures

Lotfi, Roghaye | 2013

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 46778 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Saboohi, Yadollah; Ghofrani, Mohammad Bagher
  7. Abstract:
  8. In the present work storage of hydrogen molecules in hybrid nanostructures has been evaluated. Hybrid nanostructures consist of carbon structure bases which have been doped by metal atoms. Carbon structures used in this thesis include graphene and metal organic frameworks (MOFs). Carbon structures have superior properties such as very low density, while metal atoms are considered to enhance the interactions and increase the hydrogen storage capacity. In the first step of the work, Monte Carlo method was applied to model the system. To develop the Monte Carlo method for hydrogen adsorption on graphene sheets, Feynman-Hibbs corrections were added to Lennard-Jones potential. However in the next step, due to the presence of metal atoms and lack of efficient potential for investigating interactions, it was concluded that another method rather than Monte Carlo method should be used. As a result, models based on the quantum mechanics were used to evaluate the interactions precisely. For modeling the system two methods of Moller-Plesset and Density Functional Theory were applied. In Density Functional Theory modeling, effect of van der Waals forces was added to the model separately. The results indicated that presence of metal atoms can enhance the interaction between hydrogen molecules and base structures significantly (up to eight times). To prevent metal atoms clustering over graphene sheets, structural defects were applied. In case of MOFs, replacement of carbon atoms by bore atoms was used to prevent clustering. Furthermore, in another section of the work, diffusion of hydrogen molecules through graphene sheets was assessed and it was revealed that graphene by having energy barrier of 15.82 eV is impermeable to hydrogen molecules
  9. Keywords:
  10. Hydrogen Storage ; Monte Carlo Model ; Hybrid Nanostructures ; Quantum Model

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