E-Locus - Institutional Repository of the University of Crete

Home Search

Results - Details

Search command : Author="Κουτσολέλος" And Author="Αθανάσιος"

Current Record: 15 of 125

[Add to Basket]

Identifier

000447121

Title

Σύνθεση και χαρακτηρισμός πορφυρινικών παραγώγων για φωτοκαταλυτική παραγωγή υδρογόνου

Alternative Title

Synthesis and characterization of porphyrin derivatives, for photocatalytic hydrogen production

Author

Αγαπάκη, Ελένη Γ.

Thesis advisor

Κουτσολέλος, Αθανάσιος

Reviewer

Αγγαρίδης, Παναγιώτης
Μητράκη, Άννα

Abstract

Fossil fuels are our primary energy sources; however, their combustion causes climate change due to the production of greenhouse gases such as carbon dioxide (CO₂). One of the most essential scientific challenges of this century is to reduce the ecological footprint of human activity targeting a sustainable existence of mankind on the planet. Among the available renewable energy sources, sunlight is by far the most attractive candidate, because it is vast, almost inexhaustible and clean. The sun can be used to produce a promising fuel, hydrogen. Hydrogen is rightly the fuel of the future as during its combustion the only by-product it produces is water. Photocatalytic hydrogen (H₂) production is considered to be the most promising method of converting water to hydrogen. To date, a variety of photocatalytic systems for hydrogen production have been developed. These typically use a photosensitizer (PS) that absorbs light, a catalyst (CAT) that reduces water to hydrogen, and a sacrificial electron donor (SED) that regenerates the oxidized photosensitizer (PS⁺). The purpose of this master's thesis is the synthesis and study of suitably modified porphyrins that will maximize the efficiency of the photocatalytic system. Titanium dioxide (TiO₂) after its modification with platinum nanoparticles (Pt nanoparticles) was used as a catalyst, while in order to increase the photocatalytic production of hydrogen porphyrin derivatives adsorbed on the surface of TiO₂. In the first part of the work, we examined the impact of: i) the position of the carboxyl group (ortho- or para-position) and ii) the distance between the porphyrin macrocycle and the anchoring group. It has been found that due to stereochemical inhibition the ortho adsorption of porphyrins is impossible. While referring to the the distance between the porphyrin macrocycle and the anchoring group, it was observed that the zinc porphyrins with a longer carbon chain give a lower photocatalytic efficiency. In the second part of this dissertation, porphyrins bearing four carboxyl groups and different metals in the central porphyrin ring were synthesized. The effect of size of carbon chains and different metals on the photocatalytic production of hydrogen was studied. In this part, the porphyrins with the largest carbon chains showed better results while when they were platinum mineralized, they showed the highest efficiency, achieving 10819 catalytic cycles (TONs) in just 24 hours of irradiation. The study was extended to find the best system conditions. After four different sacrificial electron donors (SEDs) and two different semiconductors, the system was found to have the highest efficiency with Ascorbic Acid (1 M) pH = 4 and TiO₂/Pt (0.5% w/w).

Language

Greek

Subject

Carboxyl groups

Energy/electron transfer

Photocatalysis

Platinum nanoparticles

TiO2/Pt

Titanium dioxide

Διοξείδιο του τιτανίου

Καρβοξυλομάδες

Μεταφορά ενέργειας / ηλεκτρονίων