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Identifier 000397563
Title Θεωρητική μελέτη προσρόφησης υδρογόνου σε νανοπορώδη υλικά
Alternative Title Theoretical study of hydrogen adsorption on nanoporous materials
Author Στεργιαννάκος, Ταξιάρχης
Thesis advisor Φρουδάκης, Γεώργιος
Reviewer Φαράντος, Σταύρος
Στούμπος, Αθανάσιος
Τρικαλίτης, Παντελής
Γουρνής, Δημήτριος
Στεριώτης, Θεόδωρος
Χαραλαμποπούλου, Γεωργία
Abstract The serious environmental problems arising from burning fossil fuels create a pressing need to find new ones, renewable and environmental friendly. One of the most prominent replacements for fossil fuel is hydrogen, but whose efficient storage has proven particularly difficult. In this thesis was studied the hydrogen storage in nanoporous materials. The research focused on hydrogen storage in porous materials type MOF, COF and ZIF modified with divalent metals. Also was designed and tested innovative porous materials with pillared structures based on elements of silicon - carbon (SiC) and boron - nitrogen (BN) for hydrogen storage. In addition was studied the binding capability of molecular hydrogen on SiC and BN materials doped with transition metals of the third series. The first part of the thesis contains the essential elements of the Hydrogen Economy such as basic hydrogen production methods, ways of distribution, main types of fuel cells and finally the main hydrogen storage methods. The present study focuses on the storage of hydrogen by physisorption to porous materials. Furthermore we present the major categories of materials which were studied for hydrogen storage. The second part of the thesis develops in detail the theory and the methodology applied in this work. The third part of the thesis presents and analyzes the results of this study. We discuss the results of calculations by “ab initio” methods of DFT, which tested the ability of the divalent metals Be Mg, Ca, Co, Cr, Cu, Fe, Mn, Ni, Ti, V and Zn to improve the storage capacity of MOF, COF and ZIF type materials, which have biphenyls or catechols as organic bridges, for molecular hydrogen. The results found that those modifications significantly improve the energy interaction of molecular hydrogen with almost all the metals studied. Next were designed modified structures of MOF-5, IRMOF-10, COF-102 and ZIF-68 with alkoxy groups of magnesium and studied, with GCMC simulations, the hydrogen storage capacity of IRMOF-10-Mg and IRMOF-10-2Mg. The simulations showed a significant increase in the volumetric and gravimetric hydrogen adsorption, mainly in small and moderate pressures, due to the presence of magnesium alkoxy groups. Also in this study were designed innovative three-dimensional nanostructured materials based on elements of silicon - carbon (SiC) and boron - nitrogen (BN). These structures are based on the structure of Pillared Graphene (PG) and consist of Graphene-type sheets and nanotubes forming three-dimensional periodic materials SiC-PG and BN-PG. The connection between the sheets and nanotubes takes place using appropriate combination of polygons (three octagons six heptagons, ...), according to the generalized Euler's rule for polygons. These innovative materials exhibit extremely interesting physicochemical properties with flexible geometries. From theoretical calculations we have found that the SiC and BN materials exhibit improved hydrogen storage capacities due to their electrostatic nature. The structural and electronic characteristics of these materials and their interaction with molecular hydrogen were studied using the theories of DFT theory (Density Functional Theory) and DFTB (Density Functional based Tight Binding). Finally, it was examined by quantum mechanical methods, the hydrogen interaction with SiC and BN materials doped with transition metals of the third series (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) with results showing improved energy interaction of molecular hydrogen with the most of transition metals, compared to non-doped SiC and BN materials.
Language Greek
Subject Fossil fuels
Ορυκτά καύσιμα
Issue date 2015-12-07
Collection   School/Department--School of Sciences and Engineering--Department of Chemistry--Doctoral theses
  Type of Work--Doctoral theses
Permanent Link https://elocus.lib.uoc.gr//dlib/e/f/b/metadata-dlib-1448965347-253984-1611.tkl Bookmark and Share
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