- B.S. (Diploma), Chemical Engineering N.T.U. Athens, 1981
- Ph.D. Chemical Engineering, University of Patras, 1989
Solid Oxide Fuel Cells and Electrolyzers
Solid oxide fuel cells (SOFC) are power generators capable of converting the chemical energy of a fuel into electrical energy and with a high temperature thermal by-product. A significant comparative advantage of SOFCs over other types of fuel cells is their ability to run directly on natural gas or other carbon-fuels, without using an external reformer, due to the catalytic action of the anode electrode at the SOFC operation temperature (Internal reforming SOFCs or IR-SOFCs). By proper selection of the anode electrocatalyst, co-generation of electrical energy and useful chemicals (chemical cogeneration) is also possible in SOFCs. A long-sought goal in SOFC research is the reduction of the operation temperature, which creates the need for development of novel materials and methods to address the issue of overpotential losses.
Our current research is related to the development and characterization, via a variety of electrochemical and catalytic methods, of new catalyst-electrodes and electrolytes for SOFC applications, in particular for intermediate temperature (600 – 800 oC) SOFCs, as well as to the study of the factors which lead to gradual degradation of fuel cell performance. Towards this direction, our research interests comprise:
(a) Development and characterization of mixed ion-electron conducting perovskitic cathodes with high activity for oxygen reduction, mainly La-Sr-Co-Fe perovskites
(b) Development and characterization of cermet anodes for SOFCs operating under internal reforming (IR-SOFC) or chemical cogeneration conditions using carbon-based fuels as well as of metal infiltrated mixed conducting ceramic anodes for redox-stable SOFCs
(c) Development and characterization of apatite-type lanthanum silicate based SOFCs.
The operation of SOFCs is in principle reversible, meaning that the fuel cell can operate in reverse or electrolysis mode, when integrated with an energy source. In this reverse operation mode the solid oxide cell operates as an electrolysis cell (solid oxide electrolysis cell, SOEC) where electric work is used to drive electrochemical reactions producing, e.g., H2 from H2O. Our research interest is also directed to the development and characterization on new catalyst-electrodes for SOEC applications, aiming mainly to addressing issues related to minimization of overpotential losses and degradation, taking into accounts the inherent differences in SOFC and SOEC operation.
Non-conventional fuel cells
Microbial fuel cells (MFCs) are devices capable of directly transforming chemical energy into electrical energy via electrochemical reactions involving biochemical pathways. In a MFC, microorganisms oxidize organic matter, under anaerobic conditions, and transfer electrons to the anode electrode. MFCs are in the early stages of development, however they have a great potential for simultaneous treatment of wastewater and energy production. Since a few years we have been cooperating with the group of Prof. G. Lyberatos (School of Chemical Engineering, NTUA, Athens, Greece) on the development of MFCs fed with by-products or wastes from food industries, such as cheese whey. Our complementary expertise in electrochemical and biochemical engineering is currently directed to scale up and optimization of these MFCs systems as well as on the detailed study of the factors affecting their performance.
Photo-electrochemical cells are devices that can either convert light to electric power (photo-fuel cells or regenerative photo-electrochemical cells) or convert light to chemicals (photosynthetic cells). Their operation is based on electron-hole pair formation initiated by band-gap excitation of a semiconductor. We are currently cooperating with the group of Prof. D. Kontarides in developing efficient photoelectrocatalysts for photo-electrochemical cells, in particular photoanodes responding efficiently to visible light.
Heterogeneous Catalysis and Electrochemical Promotion
The catalytic properties of metal or metal oxide films interfaced to solid electrolytes or mixed conductors can be dramatically and reversibly altered under conditions of polarization of the metal/solid electrolyte interface. This effect, known as Non-Faradaic Electrochemical Modification of Catalytic Activity (NEMCA effect) or Electrochemical Promotion (EP), has been intensively studied over the last 25 years for a variety of reactions, catalysts and solid electrolytes. Our research interest focuses on potential novel applications of EP in reactions of industrial and environmental importance. It also focuses on the electrochemical characterization of the catalyst-solid electrolyte system under EP conditions, in particular in the case of alkali-ion conductors, aiming to a detailed understanding of the interconnection between the electrochemical characteristics of the system and the electrochemically induced in situ promotion of the catalytic properties of the catalyst-electrode, in comparison with the corresponding ex situ catalyst promotion via classical methods.
“Dependence of Catalytic Rates on Catalyst Work Function”, C.G. Vayenas, S. Bebelis, S. Ladas, Nature 343 (6259) (1990) 625-627
"The Origin of non-Faradaic Electrochemical Modification of Catalytic Activity", S. Ladas, S. Kennou, S. Bebelis, C.G. Vayenas, J. Phys. Chem. 97(35) (1993) 8845-8848
“Electrochemical promotion of the oxidation of propane on Pt/YSZ and Rh/YSZ catalyst electrodes", N. Kotsionopoulos, S. Bebelis, J. Appl. Electrochem. 35(12) (2005) 1253-1264
“Electrochemical characterization of perovskite-based SOFC cathodes, S. Bebelis, N. Kotsionopoulos, A. Mai, F. Tietz, J. Appl. Electrochem. 37 (2007) 15-20
“AC Impedance characterization of a La0.8Sr0.2Co0.2Fe0.8O3-δ electrode”, V. Ch. Kournoutis, F. Tietz, S. Bebelis, Fuel Cells 9(6) (2009) 852-860
“Cyclic voltammetry characterization of a La0.8Sr0.2Co0.2Fe0.8O3-δ electrode interfaced to CGO/YSZ”, V. Ch. Kournoutis, F. Tietz, S.Bebelis, Solid State Ionics 197(1) (2011) 13-17
“Operation and characterization of a microbial fuel cell fed with pretreated cheese whey at different organic loads”, A. Tremouli, G. Antonopoulou, S. Bebelis, G. Lyberatos, Bioresource Technology 131 (2013) 380-389