Unit:
Department of ChemistryLibrary of the School of Science
Dissertation committee:
ΠΑΝΑΓΙΩΤΗΣ ΚΥΡΙΤΣΗΣ, Καθηγητής, Τμήμα Χημείας ΕΚΠΑ
ΧΡΙΣΤΙΑΝΑ ΜΗΤΣΟΠΟΥΛΟΥ Καθηγήτρια ΕΚΠΑ
ΘΕΟΔΩΡΟΣ ΣΤΕΡΙΩΤΗΣ Διευθυντής Ερευνών, ΙΝΝ, ΕΚΕΦΕ «Δημόκριτος»
ΙΩΑΝΝΗΣ ΠΑΠΑΕΥΣΤΑΘΙΟΥ Καθηγητής ΕΚΠΑ
ΕΛΕΝΗ ΕΥΘΥΜΙΑΔΟΥ Επίκουρος Καθηγήτρια ΕΚΠΑ
ΚΩΝΣΤΑΝΤΙΝΟΣ ΜΕΘΕΝΙΤΗΣ Αναπληρωτής Καθηγητής ΕΚΠΑ
ΓΕΩΡΓΙΑ ΧΑΡΑΛΑΜΠΟΠΟΥΛΟΥ Διευθύντρια Ερευνών, ΙΠΡΕΤΕΑ, ΕΚΕΦΕ «Δημόκριτος»
Original Title:
Development of nanocomposite materials for hydrogen storage
Translated title:
Development of nanocomposite materials for hydrogen storage
Summary:
Borohydrides are considered good candidates for low-pressure solid state hydrogen storage, as they have very high hydrogen content. However their high stability and decomposition temperatures hinder their practical use. An appealing approach for adjusting their thermodynamic properties is nano-sizing by confinement in nanometersized pores. The aim of this thesis has been to study the hydrogen storage-release properties of eutectic borohydride mixtures such as LiBH4 – NaBH4 (LiNa) and LiBH4 – KBH4 (LiK), after their incorporation (through melt infiltration) in mesoporous carbonaceous materials. It has been shown that the confinement of the borohydride mixtures into 5 and 25 nm diameter pores of a CMK-3 type carbon and a carbon aerogel (CA-20), respectively, improves the kinetics, also providing a partial reversibility of the dehydrogenation / rehydrogenation reaction for both eutectic mixtures after 5 cycles. While the dehydrogenation reactions of the bulk complex hydrides are irreversible, the nanoconfined systems exhibit a consistent reversible uptake of about 3.5-4 wt% H2 for the LiNa / CMK-3 and CA-20 composites and about 3 wt% H2 for the LiK ones. The same synthetic procedure was also followed to obtain composite materials with non-porous carbon disks (CD) and kinetic improvements in the hydrogen release properties of the borohydrides were also observed. These findings in the absence of porosity imply that the carbon surface may act catalytically and assist the decomposition of the borohydrides. However, the pore nanoconfinement seems to play a fundamental role in the reversibility of the hydrogenation reaction, at least for the case of the LiBH4 – KBH4 mixture. Overall, this thesis revealed that the increased reversibility and improved kinetics may be related to a combination of several phenomena such as the catalytic action of the carbon surface, the nano-sizing of the borohydride particles, and/or the abatement of irreversible side-reactions.
Main subject category:
Science
Keywords:
Hydrogen storage, mesoporous materials, nanoconfinement, complex hydrides, borohydrides, eutectic mixtures
Number of references:
339
