Τμήμα Επιστήμης & Μηχανικής Υλικών​

Παρουσίαση Μεταπτυχιακής Διπλωματικής Εργασίας της κ. Μαρίας Μεταξά

02 Ιουλίου 2025

ΠΑΝΕΠΙΣΤΗΜΙΟ ΚΡΗΤΗΣ

ΤΜΗΜΑ ΕΠΙΣΤΗΜΗΣ ΚΑΙ ΜΗΧΑΝΙΚΗΣ ΥΛΙΚΩΝ

 ΠΑΡΟΥΣΙΑΣΗ ΜΕΤΑΠΤΥΧΙΑΚΗΣ ΔΙΠΛΩΜΑΤΙΚΗΣ ΕΡΓΑΣΙΑΣ

Τίτλος

«Interfacial Engineering of Co(OH)₂/CdIn₂S₄ Nano-heterostructures for Enhanced Electrochemical Water Splitting»  

της Μαρίας Μεταξά

μεταπτυχιακής φοιτήτριας του Τμήματος Επιστήμης και Μηχανικής Υλικών του Πανεπιστημίου Κρήτης

Επιβλέπων Καθηγητής: Γεράσιμος Αρματάς

Δευτέρα 7 Ιουλίου 2025

Ώρα 13:00

H παρουσίαση θα πραγματοποιηθεί στην αίθουσα Τηλε-εκπαίδευσης (Ε130), στο κτήριο του Τμήματος Μαθηματικών και Εφαρμοσμένων Μαθηματικών, του Πανεπιστημίου Κρήτης

Abstract

Hydrogen is a key component of future clean energy systems due to its high energy density and zero carbon emissions when used as a fuel. Sustainable hydrogen production via electrocatalytic water splitting, powered by renewable electricity, is vital for achieving carbon-neutral energy solutions. However, the efficiency of this process is hindered by the oxygen evolution reaction (OER), which suffers from sluggish kinetics and high overpotentials, necessitating the development of robust and efficient electrocatalysts.

This thesis presents a novel nanostructured electrocatalyst composed of cobalt hydroxide (β-Co(OH)₂) nanosheets anchored on CdIn₂S₄ (CIS) thiospinel nanoparticles. The hybrid Co@CIS heterostructure was synthesized via a combination of hydrothermal and photochemical deposition methods. Comprehensive characterization techniques, including X-ray diffraction (XRD), high-energy X-ray diffuse scattering (HE-XRDS), scanning and transmission electron microscopy (SEM/TEM), X-ray photoelectron spectroscopy (XPS), UV–Vis spectroscopy, were employed to probe the structural, morphological and electronic properties under OER working conditions. Electrochemical impedance spectroscopy (EIS) was used to assess charge-transfer dynamics and intrinsic activity. The results reveal the formation of a well-defined p–n heterojunction at the Co(OH)₂/CIS interface, significantly enhancing directional charge carrier transport and reducing interfacial resistance to improve reaction kinetics. In-situ Raman spectroscopy reveals an irreversible transformation of Co(OH)2 to the catalytically active CoOOH phase under anodic polarization, which correlates with enhanced OER performance. The optimized Co@CIS electrocatalyst exhibits high OER performance with a low overpotential of 294 mV and a small Tafel slope of 61.2 mV dec⁻¹ at 10 mA cm⁻² in alkaline electrolyte, while maintaining excellent operational durability for over 40 hours. When, integrated into a two-electrode alkaline electrolyzer (with Pt/C as cathode electrode), water electrolysis required a cell voltage of 1.60 V to generate a current density of 10 mA cm^-2, corresponding to an electrical-to-fuel efficiency of 77%.

These findings highlight the effectiveness of rationally engineering the interface between semiconductor-based materials to simultaneously enhance the intrinsic catalytic activity and long-term stability of electrocatalysts for alkaline OER.