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Identifier

000465728

Title

Porous mesoscopic assemblies of spinel chalcogenide and transition metal phosphide nanoparticles for photocatalytic energy conversion applications

Alternative Title

Πορώδη μεσοσκοπικά δίκτυα νανοσωματιδίων χαλκογονιδίου σπινελίου και φωσφιδίου μετάλλου μετάπτωσης για εφαρμογές φωτοκαταλυτικής μετατροπής ενέργειας

Author

Ανδρέου, Ευάγγελος

Thesis advisor

Αρματάς, Γεράσιμος

Reviewer

Κιοσέογλου, Γεώργιος
Στούμπος, Κωνσταντίνος
Κοπιδάκης, Γεώργιος
Τρικαλίτης, Παντελής
Μήλιος, Κωνσταντίνος
Δεληγιαννάκης, Ιωάννης

Abstract

The persistent rise in fossil fuel consumption, driven by the need to satisfy current energy demands, poses a significant environmental hazard, primarily due to the substantial emissions of hazardous gases into the atmosphere. While it is evident that renewable energy sources must replace a significant portion of fossil fuels, existing renewable energy production methods often lack efficiency and still present environmental challenges. Photocatalytic water splitting for hydrogen production stands out as a low-cost technique, offering a high solar to chemical conversion efficiency while emitting zero hazardous gases. Over the last few decades, the research community has explored various photocatalysts, including metal oxides, chalcogenides, nitrides, and more. Despite considerable progress in the development of photocatalytic materials, current synthetic methods often fail to provide precise control over electrochemical properties, morphology, and size of particles, leading to subpar photocatalytic performance. In this dissertation, we introduce a new, cost-effective and environmentally friendly synthetic protocol for fabricating mesoporous networks of interconnected thiospinel (MIn2S4, M = Zn, Cd) nanocrystals, serving as versatile building blocks. This synthetic approach provides the advantage of adjusting the size of the constituent inorganic nanocrystals, offering significant benefits for photocatalytic energy conversion applications. Such a controllable synthesis enables precise engineering of the optical and electronic properties of the resulting photocatalysts. Namely, employing a straightforward polymer-templated self-assembly process, the thiospinel nanocrystals are organized into three-dimensional (3D) mesoporous networks with large internal surface area and we-defined pores. This structural arrangement leads to improved charge transfer kinetics and better intraparticle diffusion of the electrolyte. Given their advantageous characteristics, the mesoporous ensembles were investigated as potential photocatalysts for the water splitting reaction towards hydrogen evolution. Furthermore, by carefully selecting suitable co-catalysts such as Ni2P, Co2P, and β-Ni(OH)2, we uncovered their significant impact on the photochemical properties of the resulting composite structures. Utilizing a combination of spectroscopic and (photo)electrochemical techniques, we identified that the formation of the thiospinel/metal phosphide/hydroxide nano-heterojunctions significantly enhances the separation and transfer ability of the photogenerated charge carriers, leading to high photocatalytic stability and activities. Notably, these improvements exceed those reported for previously studied high-performance multicomponent thiospinel-based photocatalytic systems. Overall, this research presents a novel synthetic perspective for the rational design of photocatalysts and advances our understanding of next generation photocatalysts for clean energy conversion applications. By shedding light on key aspects of inorganic synthetic chemistry, interface engineering and photochemical reactions, the findings of this work make a significant contribution to the broader research endeavor focused on the development of sustainable energy technologies

Language

English

Subject

Hydrogen evolution

Mesoporous

Nanomaterials

Photocatalysis

Thiospines

Θειοσπινέλια

Νανουλικά Μεσοπορώδη υλικά

Παραγωγή υδρογόνου

Φωτοκατάλυση