Post-graduate theses
Current Record: 34 of 123
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| Identifier |
000444324 |
| Title |
Mesoporous networks of MoS2 and CdS nanoparticles as photocatalysts for water splitting and hydrogen production |
| Alternative Title |
Μεσοπορώδη δίκτυα νανοσωματιδίων MoS2 και CdS ως φωτοκαταλύτες για τη διάσπαση του νερού προς παραγωγή υδρογόνου |
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Author
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Πατριαρχέα, Χρυσάνθη
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Thesis advisor
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Αρματάς, Γεράσιμος
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Reviewer
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Ρεμεδιάκης , Ιωάννης
Στούμπος, Κωνσταντίνος
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| Abstract |
Hydrogen production by water-splitting photocatalysis has attracted significant interest in recent years as a low-cost and environmentally friendly process. Generally, a tremendous number of semiconductors have been developed that fulfil the criteria of effective photocatalysts such as appropriate band gap (1.23–3.26 eV) and suitable reduction and oxidation band position. However, due to the fast recombination process of the photoinduced carriers and low efficiency of the photon to hydrogen conversion, it is essential to construct new heterostructures with intimate contact between the components and pronounced visible-light absorption for achieving high photocatalytic performance. This thesis focuses on synthesis and characterization of new mesoporous heterojunction networks consisted of ultrasmall MoS2 nanolayers (ca. 10–15 nm in lateral size) and sub 5 nm sized CdS nanocrystals. The application of these nanostructures as photocatalysts for H2 generation from water splitting is also studied. To prepare these nanocomposite materials we used a polymer-templated oxidative aggregating method for CdS nanocrystal assemblies followed by a wet-chemical deposition of exfoliated MoS2 nanosheets on CdS surface. The chemical composition and the morphological and structural properties of the catalysts were investigated with electron microprobe analysis (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electron microscopy (ΤΕΜ) and N2 physisorption. The results indicated that the MoS2-modified CdS nanocatalysts consist of a porous network of connected cubic CdS nanocrystals and 2H-phase MoS2 nanosheets and exhibit large internal BET surface area (ca. 159–225 m2 g-1) and uniform pores (ca. 6–9 nm in diameter). Photocatalytic H2 evolution experiments coupled with UV–vis/NIR absorption, time-resolved photoluminescence (TRPL) and electrochemical impedance spectroscopy (EIS) measurements revealed that the superior photocatalytic activity in
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these materials arises from the efficient dissociation and transport of photogenerated charge carriers across the nanoscale MoS2/CdS junctions and the large number of exposed active sites due to the 3D open-pore structure. The optimized MoS2/CdS catalyst at 20 wt.% MoS2 content achieves a H2 evolution rate of ~0.4 mmol h-1 (or ~19 mmol h−1 g−1 mass activity) under visible light irradiation, which is 6.7 times higher than that of unmodified mesoporous CdS. We also obtained an apparent quantum yield (AQY) of 51.2% for hydrogen generation reaction using monochromatic light of 420 nm. The results of this study present an understanding of the charge transfer dynamics at the MoS2/CdS nanoscale junctions and support the potential viability of the MoS2-modified CdS nano-heterostructures as photocatalysts for clean energy conversion.
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| Language |
English |
| Issue date |
2021-11-26 |
| Collection
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School/Department--School of Sciences and Engineering--Department of Materials Science and Technology--Post-graduate theses
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Type of Work--Post-graduate theses
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| Permanent Link |
https://elocus.lib.uoc.gr//dlib/0/a/2/metadata-dlib-1639992735-352354-14848.tkl
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| Views |
258 |
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