PhD Thesis Defence Presentations - Alexandros Safakas

Presentation Type (Τύπος Παρουσίασης): PhD Thesis Defence Presentations
Speakers Full Name (Ονοματεπώνυμο): Alexandros Safakas
Speakers Affiliation (Προέλευση Ομιλητή): Department of Chemical Engineering, University of Patras
Seminar Room (Αίθουσα): Seminar Hall
Event Date: Tue, Mar 26 2019, Time: 12:00 - 13:30
Abstract (Περίληψη)

A comparative assessment of the behavior of a series of eight (8) perovskite oxides with general formula La0.8Sr0.2CoxFe1-xO3 (including La0.8Sr0.2FeO3 and La0.8Sr0.2CoO3) was conducted, as catalysts for CO and propane combustion and as oxygen reduction electrocatalysts for application in high temperature solid oxide fuel cells as well as in low temperature alkaline fuel cells. The main conclusion derived from the study of the catalytic behavior of La0.8Sr0.2CoxFe1-xO3 powders for CO and propane oxidation, under oxidative and stoichiometric feed conditions, was that the catalytic activity increased with increasing Co/Fe ratio in the perovskite composition, this effect being more pronounced for oxidative conditions. The study of the impedance characteristics of La0.8Sr0.2CoxFe1-xO3 electrodes interfaced to CeO2-Gd2O3 electrolyte under oxygen partial pressures PO2 ranging from 0.7 to 100 kPa and temperatures from 600 to 850 οC revealed that these characteristics were determined by up to two main processes whose relative contribution in shaping the open circuit total polarization resistance depended on PO2, temperature and Co/Fe ratio. Finally, the study of electrocatalysts composed of a mixture of La0.8Sr0.2CoxFe1-xO3 and carbon black (performed mainly via the rotating disk technique) as it concerns oxygen reduction in alkaline medium at  room temperature showed that gradual substitution of Fe by Co in the oxide’s composition results in increase of the electrocatalytic activity. Also, an increase in the number of transferred electrons was found, from ca. 2 for La0.8Sr0.2FeO3/C to ca. 4 for La0.8Sr0.2CoO3/C, implying a gradual change in the reaction mechanism. In all above cases, the origin of the observed behavior was associated with changes in the electronic structure of the surface B-sites (Co- and Fe-sites) induced by changing the Co/Fe ratio, as well as with changes in the concentration of oxygen vacancies.

Speakers Short CV (Σύντομο Βιογραφικό Ομιλητή)


2007: Diploma (M.S.) in Mechanical Engineering and Aeronautics, Department of Mechanical Engineering and Aeronautics, University of Patras, Greece


Publications and Conference participation

Oxygen reduction reaction on La0.8Sr0.2CoxFe1-xO3-δ perovskite/carbon black electrocatalysts in alkaline medium.

Alexandros Safakas, Georgios Bampos, Symeon Bebelis,

Applied Catalysis B: Environmental Volume 244, 5 May 2019, Pages 225-232

Oxygen Reduction Reaction on La0.8Sr0.2CoxFe1-xO3-δ/C in Alkaline Medium

Georgios Bampos, Alexandros Safakas, Symeon Bebelis,

69th Annual Meeting of the International Society of Electrochemistry, 2-7 September 2018, Bologna, Italy

Electrochemical Impedance Study of the Oxygen Reduction Reaction on La0.8Sr0.2CoxFe1-xO3-δ/C Electrocatalysts in Alkaline Medium

Alexandros Safakas, Georgios Bampos, Symeon Bebelis

25th Topical Meeting of the International Society of Electrochemistry, New Electrochemical processes for energy and the environment, 12-15 May 2019, Toledo, Spain 


Research interests

Perovskite oxides in catalytic and electrocatalytic applications

Electrochemical Impedance Spectroscopy (EIS) and Rotating Disk Electrode technique (RDE)

Solid Oxide Fuel Cells

Electrode deposition techniques in solid electrolytes

Oxygen reduction reaction (ORR) in alkaline media