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https://olympias.lib.uoi.gr/jspui/handle/123456789/40245Full metadata record
| DC Field | Value | Language |
|---|---|---|
| dc.contributor.author | Belles, Loukas | en |
| dc.contributor.author | Μπελλές, Λουκάς | el |
| dc.date.accessioned | 2026-07-10T07:25:24Z | - |
| dc.identifier.uri | https://olympias.lib.uoi.gr/jspui/handle/123456789/40245 | - |
| dc.rights | Default License | - |
| dc.subject | Nanomaterials | en |
| dc.subject | Flame Spray Pyrolysis | en |
| dc.subject | H2 Photocatalysis | en |
| dc.subject | H2 Photoelectrocatalysis | en |
| dc.subject | CO2 reduction reaction | en |
| dc.subject | Zirconia (ZrO2) | en |
| dc.subject | Zr-based nanomaterials | en |
| dc.subject | ZrO2 Quantum Dots | en |
| dc.subject | Interfacial Quantum States | en |
| dc.title | Development of nanostructured microsystems for photoelectrocatalytic energy technology | en |
| dc.title | Ανάπτυξη Νανοδομημένων Μικροσυστημάτων για φωτοηλεκτροκαταλυτικές ενεργειακές τεχνολογίες | el |
| dc.type | doctoralThesis | en |
| heal.type | doctoralThesis | el |
| heal.type.en | Doctoral thesis | en |
| heal.type.el | Διδακτορική διατριβή | el |
| heal.dateAvailable | 2029-07-09T21:00:00Z | - |
| heal.language | en | el |
| heal.access | embargo | el |
| heal.recordProvider | Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών | el |
| heal.publicationDate | 2026-06-22 | - |
| heal.abstract | This PhD thesis focuses on the design, synthesis, structural control and catalytic application of zirconia-based nanostructured materials for energy-conversion technologies as photocatalytic hydrogen (H2) production, electrocatalytic carbon dioxide (CO2) reduction and oxygen reduction (ORR) reactions. Although ZrO2 is a wide-band-gap, in the range of about 5–6 eV, depending on crystal phase, which underlines the challenge—but also the opportunity—of activating zirconia for energyconversion reactions. This semiconductor is weakly conductive and relatively inert oxide, this work explores how its catalytic and photoelectrocatalytic functionality can be activated through nanoscale engineering. Particular emphasis is placed on flame spray pyrolysis technology (FSP) as a scalable synthesis platform for controlling ZrO2 phase composition, particle size, defect chemistry and heterointerface formation. By modifying FSP configurations, including single-nozzle, doublenozzle and low-temperature injection approaches, tetragonal/monoclinic ZrO2 ratios, oxygendeficient ZrO2-x domains and metal-oxide heterostructures were systematically engineered. The first part of the thesis investigates how to reach the desired phase composition for ZrO2 nanoamterials through single nozzle FSP process. Until our recent work FSP-made ZrO2 had a specific ratio of monoclinic/tetragonal phases of 10:90 - 20:80 (%), in this chapter we show how we achieved to fully control this ratio up to a limit of 90:10 (%). Additionally, the influence of ZrO2 polymorphism on photocatalytic hydrogen production was investigated. Phase-controlled FSPmade ZrO2 nanomaterials demonstrated that tetragonal-rich zirconia exhibits superior activity compared with monoclinic-rich analogues, reaching an H₂ evolution rate of 10,150 μmol g⁻¹ h⁻¹ under identical testing conditions. The second part develops CuO/ZrO2 by FSP again with a setup of a single nozzle open FSP and after the nanocatalysts are partially reduced CuO/Cu2O–ZrO2 heterostructures, where strong interfacial coupling between copper oxides and zirconia enhances visible-light absorption, charge separation and interfacial electron transfer. The optimized reduced CuO/Cu2O–ZrO2 system achieved an H₂ production rate of 6,080 μmol g⁻¹ h⁻¹, highlighting the importance of mixed copper oxide phases strongly interfaced with ZrO2. A central contribution of the thesis is the development of ZrO2/ZrO2-x quantum-dot systems for first time with controllable main particle size of 2–5 nm, where a crystalline ZrO2 quantum-dot core is coupled with a semi-amorphous oxygen-deficient ZrO2-x layer. This architecture creates interfacial quantum states that enable sub-bandgap absorption, charge-carrier stabilization and efficient photocatalytic H₂ evolution. The optimized ZrO2/ZrO2-x quantum-dot material achieved a benchmark H₂ production rate above 32,000 μmol g⁻¹ h⁻¹ with an apparent quantum yield of 3.49% at 252 nm, demonstrating that wide-band-gap oxides can be activated through precise defect and interface engineering. Finally, the thesis introduces an RRDE-assisted methodology for rapid product detection during CO₂ electroreduction on Zr-based powder nanocatalysts, including ZrO2, Bi2O3/ZrO2 and Bidecorated ZrO2 systems. This method contributes to overcoming the threshold of need of many analytical instruments such as HPLC, NMR and UV-Vis DRS. This protocol combines disk electrolysis, ring-based product oxidation and HPLC validation to evaluate formic acid/formate formation and therefore Faradaic efficiency. After this validation and calibration for each targeted C1 liquid product, this method can be a stand-alone method for determining the CO2 product and the quantity of it. Overall, this thesis establishes ZrO2 not as an inert support, but as an active and tunable platform for energy applications. The results demonstrate that phase control, quantum-size reduction, oxygen-vacancy engineering and heterointerface design can unlock new catalytic functions in zirconia-based nanomaterials such as electrocatalytic, photocatalytic and photoelectrocatalytic applications as H2 evolution and CO2 reduction. | en |
| heal.advisorName | Δεληγιαννάκης, Ιωάννης | el |
| heal.committeeMemberName | Μπουρλίνος, Αθανάσιος | el |
| heal.committeeMemberName | Τσιπλακίδης, Δημήτριος | el |
| heal.committeeMemberName | Λουλούδη, Μαρία | el |
| heal.committeeMemberName | Μπουρμπάκης, Ιωάννης | el |
| heal.committeeMemberName | Μάρκου, Αναστάσιος | el |
| heal.committeeMemberName | Νιάκολας, Δημήτριος | el |
| heal.committeeMemberName | Δεληγιαννάκης, Ιωάννης | el |
| heal.academicPublisher | Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Φυσικής | el |
| heal.academicPublisherID | uoi | el |
| heal.numberOfPages | 342 | el |
| heal.fullTextAvailability | true | - |
| Appears in Collections: | Διδακτορικές Διατριβές - ΦΥΣ | |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| phD Thesis_Belles.pdf | 15.99 MB | Adobe PDF | View/Open Request a copy |
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