George E. Marnellos

University of Western Macedonia | UOWM · Department of Mechanical Engineering

The current work explores the feasibility to improve the performance of a Direct Carbon Fuel Cell (DCFC): CO 2 + bituminous coal|Co-CeO 2 /YSZ/Ag|Air by infusing a gasification catalyst (Co/CeO 2 ) and/or Li-K carbonates mixture into the carbon fuel. The different fuel feedstock mixtures were characterized by various methods, involving chemical com...

Infiltration is an effective way to improve porous electrode performance of solid oxide cells while the preparation procedure and catalyst stability still remain challenging. The microchannel structure of cathodes enables the implementation of catalysts into conventional Ni-based cathode supports of solid oxide electrolysis cells via the infiltrati...

Hydrogen sulphide (H2S) is one of the most poisonous and corrosive chemical substances existing in several natural and industrial gas streams, further considered as a valuable H2 source. Hence, H2S decomposition to H2 is of paramount importance toward a sustainable energy future. In the present work, the catalytic decomposition of H2S is explored i...

This study has demonstrated that microchanneled cathode supports of solid oxide electrolysis cells were developed to improve CO2 electrolysis performance. Through numerous channels embedded within the support, gas species can diffuse quickly to/from the reaction zone near the cathode/electrolyte interface, and efficient catalyst delivery to the rea...

Gas diffusion within supporting cathodes of solid oxide electrolysis cells (SOECs) plays an important role in CO2 electrolysis process. This study has investigated the effect of cathode pore structure on gas diffusion during CO2 electrolysis. The cathode pore structure was adjusted by applying the different amounts of pore former during cathode pre...

The present work explores the feasibility of an integrated and autonomous scaled up process towards the remediation of the Black Sea ecosystem with simultaneous H2 generation through the co-electrolysis of rich H2S/H2O seawater mixtures. The core unit of the proposed process is a proton-conducting membrane cell stack reactor (electrolyzer), where H...

In the present work, the feasibility of producing and simultaneously separating hydrogen from coal steam gasification (CSG) in a protonic ceramic membrane reactor (PCMR) is demonstrated. A Cu/BZCY81/Ni-BZCY72 tubular cell was employed as the PCMR for the studies. Saturated steam was fed over a mixture of powdered carbon black and K2CO3 gasification...

The combined impact of carbon type (anthracite coal, bituminous coal and pine charcoal) and in situ, catalyst-aided, carbon gasification process on the electrochemical performance of a Direct Carbon Fuel Cell (DCFC) is explored. The effect of operation temperature (700-800 oC) and catalyst (Co/CeO2) infusion to carbon feedstock under CO2 atmosphere...

CO 2 hydrogenation to value added chemicals/fuels has gained considerable interest, in terms of sustainable energy and environmental mitigation. In this regard, the present work aims to investigate the CO 2 methanation performance of cobalt-based catalysts supported on different metal oxides (M x O y : CeO 2 , ZrO 2 , Gd 2 O 3 , ZnO) at low tempera...

The present work aims to explore the impact of the support (MxOy: Al2O3, TiO2, Fe2O3, CeO2, ZnO) on the CO2 hydrogenation activity of supported gold nanoparticles (Au/MxOy) at atmospheric pressure. The textural, redox and surface properties of Au/MxOy catalysts were evaluated by various characterisation methods, namely N2 adsorption-desorption at −...

Cobalt-cerium mixed oxides were prepared by the wet impregnation method and evaluated for volatile organic compounds (VOCs) abatement, using ethyl acetate (EtAc) as model molecule. The impact of Co content on the physicochemical characteristics of catalysts and EtAc conversion was investigated. The materials were characterized by various techniques...

The aim of this work is to explore the influence of the support () on the physicochemical characteristics and the N 2 O decomposition (deN 2 O) performance of supported gold nanoparticles (Au/M x O y). Both the bare oxides and the Au/oxide catalysts were characterized by several methods (BET, XRD, SEM, HR-TEM, XPS and H 2-TPR) and comparatively eva...

The electrochemical performance of Co3O4/CeO2 mixed oxide materials as electrodes, when exposed to H2S/H2O atmospheres, was examined employing a proton conducting symmetrical cell, with BaZr0.7Ce0.2Y0.1O3 (BZCY72) as the solid electrolyte. The impact of temperature (700 – 850 oC) and H2S concentration (0 – 1 v/v%) in steam-rich atmospheres (90 v/v%...

Different lanthanide (Ln)-doped cerium oxides (Ce0.5Ln0.5O1.75, where Ln: Gd, La, Pr, Nd, Sm) were loaded with Cu (20 wt . %) and used as catalysts for the oxidation of ethyl acetate (EtOAc), a common volatile organic compound (VOC). For comparison, both Cu-free (Ce-Ln) and supported Cu (Cu/Ce-Ln) samples were characterized by N2 adsorption at −196...

The promoting impact of potassium (0–1 wt% K) on nitrous oxide (N2O) catalytic decomposition over Ir/Al2O3 is investigated under both oxygen deficient and oxygen excess conditions. All samples were characterized by means of X-ray powder diffraction (XRD), temperature-programmed reduction (H2-TPR), ammonia desorption (NH3-TPD) and Fourier Transform...

Catalytic Ethanol Steam Reforming over CeO2 supported transition metal catalysts

The aim of the present work was to investigate steam reforming of ethanol with regard to H2 production over transition metal catalysts supported on CeO2. Various parameters concerning the effect of temperature (400–800 °C), steam-to-carbon (S/C) feed ratio (0.5, 1.5, 3, 6), metal entity (Fe, Co, Ni, Cu) and metal loading (15–30 wt.%) on the catalyt...

The present study aims to examine and evaluate the concept of H2S decomposition to H2 production in (H2)-conducting electrochemical reactors. In such a complex process, one of the major issues raised is the optimal selection of materials for the electrochemical cell. Specifically, the anode electrode should exhibit high catalytic activity and elect...

The internal reforming of iso-octane is examined in a solid oxide fuel cell of the type Cu-CeO2/YSZ/Pt. The results show that i-C8H18 is efficiently reformed by H2O to syngas over Cu/CeO2 composites, free of carbon deposits. Apart from iso-octane reforming, the products distribution at open circuit conditions is also influenced by the associated i-...

This study explores strategies to develop highly efficient direct carbon fuel cells (DCFCs) by combining a solid-oxide fuel cell (SOFC) with a catalyst-aided carbon-gasification process. This system employs Cu/CeO2 composites as both anodic electrodes and carbon additives in a cell of the type: carbon|Cu-CeO2/YSZ/Ag|air. The study investigates the...

The feasibility of employing lignite coal as a fuel in a Direct Carbon Fuel Cell (DCFC) of the type: lignite/Co-CeO2/YSZ/Ag/air is investigated. The impact of several parameters, related to anodic electrode composition (20, 40 and 60 wt.% Co/CeO2), cell temperature (700-800 oC), carrier gas composition (CO2/He mixtures), and total feed flow rate (1...

The present work aims at investigating the catalytic decomposition of N2O over CuO–CeO2 single or mixed oxides prepared by different synthesis routes, i.e., impregnation, precipitation and exotemplating. To gain insight into the particular role of CeO2 as well as of CuO–CeO2 interactions, three different types of materials were prepared and tested...

Τhe feasibility of tailoring the iso-octane steam reforming activity of Cu/CeO2 catalysts through the use of Co as a second active metal (Cu20−xCox, where x = 0, 5, 10, 15, 20 wt%), is investigated. Characterization studies, involving N2 adsorption–desorption at −196 °C (BET), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), X-ray Photo...

The deN 2 O performance of low content (0.25, 0.5 and 1.0 wt. %), Al 2 O 3 supported noble metals (Pt, Pd, Ir) is comparatively explored in the present study. Several parameters related to the effect of temperature, metal content and feed composition are investigated. An extensive characterization study involving BET, TPR, XRD and TEM was also carr...

The potential of direct utilization of lignite coal in a Direct Carbon Fuel Cell (DCFC) of the type: lignite|Co-CeO 2 /YSZ/Ag|air is investigated in the present study. The impact of several parameters, related to anodic electrode composition (20, 40 and 60 wt.% Co/CeO 2), operation temperature (700-800 °C), carrier gas composition (CO 2 /He mixture...

The impact of carbon type on the performance of the direct carbon fuel cell (DCFC) or hybrid carbon fuel cell (HCFC) is investigated by utilizing bare carbon or carbon/carbonate mixtures as feedstock, respectively. In this regard, four different types of carbons, i.e. bituminous coal (BC), demineralised bituminous coal (DBC), anthracite coal (AC) a...

The present work aims to investigate the steam reforming (SR) of liquid hydrocarbons toward hydrogen production, employing iso-octane as gasoline surrogate, over Cu catalysts supported on rare earth oxides (REOs). An extensive characterization study, involving X ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectros...

This work presents performance of an i-C8H18 internal steam reforming solid oxide fuel cell (SOFC) with Co/CeO2 as anodic electrode. Initially, the catalytic activity of bi-metallic Cu-Co ceria-supported catalysts for i-C8H18 steam reforming was examined. In all cases, gas mixtures rich in ?2, CO, CO2 and CH4 were produced. Among all samples tested...

The feasibility of developing highly efficient Direct Carbon Fuel Cells (DCFCs) by merging the solid oxide fuel cell (SOFC) technology with a catalyst-aided internal carbon gasification process is explored in the present study. Toward this direction, Cu/CeO 2 catalysts are employed as anodic electrodes, whereas Cu-Co/CeO 2 catalysts with different...

This work targets to explore the performance of Cu–CeO2 anodes for the production of hydrogen and power generation during the internal steam reforming of CH3COOH in SOFC reactors. When the cell operated as an electrochemical membrane reactor, the effect of temperature, reactants' partial pressures and imposed overpotentials on the catalytic activit...

This work aims to investigate the efficiency of Cu–CeO2 as anodic composites in direct CH3COOH fed SOFC reactors for power generation. When the cell operated as an electrochemical membrane reactor, the effect of temperature, PCH3COOH and anodic overpotentials on the catalytic activity and selectivity of Cu/CeO2 for CH3COOH decomposition and electro...

The present study aims at investigating the role of potassium (K) promoter on the surface and catalytic behavior of Pd/Al2O3 catalysts during N2O reduction by alkanes (CH4, C3H8) or alkenes (C3H6). In this context, the surface properties of un-promoted and K-promoted catalysts were evaluated by means of X ray photoelectron spectroscopy (XPS), in si...

In the present work, two different methods of catalyst promotion, the electrochemical promotion (EP) and the conventional promotion (CP), were comparatively applied on a catalytic system of significant environmental and practical importance: the N2O reduction by hydrocarbons (alkanes and alkenes), in the presence or absence of O2, over Pd catalysts...

Mathematical modeling of transport and electrochemical phenomena within SOFCs can lead to improved understanding of the involved physical, electrical, and chemical processes and represents a powerful tool for their development. In this context, the present work illustrates a three-dimensional CFD simulation of a planar SOFC unit cell fuelled by mod...

The present work aims to explore the activity of Cu/CeO2 composites as anodic electrodes in direct iso-octane SOFCs. When the cell was operated as a membrane reactor, the effect of temperature, Pi-C8H18 and applied anodic overpotentials on the electrocatalytic activity and products' distribution, at both open and closed circuit conditions, was exam...

In the present work the basic transport processes occurring in a planar solid oxide fuel cell (SOFC) were simulated. The Navier–Stokes and energy equations, including convective and diffusive terms, were numerically solved by the commercial CFD-ACE+ program along with the mass and charge transport equations. To achieve this, a three-dimensional geo...

The proposed work aims to the development of a concrete theoretical background that will be used as the basis of fundamental knowledge regarding the complex process of H2S utilization in H+ conducting cells for the cogeneration of H2, H2SO4 and/or electricity. To this end, CFD simulation studies will be employed in order to define all transport phe...

It is a common point for the current fuel cell research to correlate the composition of the feedstream to the output of a Solid Oxide Fuel Cell (SOFC). In this direction, the detailed steady-state transport processes (i.e. the flow regime, the heat transfer, the mass and the charge transport) are mathematically described here. A new mesoscopic math...

A double chamber SrCe0.95Yb0.05O3 − a proton conducting membrane reactor was used in order to explore N2O and NO cathodic reduction, over Pd cathodes, by hydrogen generated from steam electrolysis at the anode. Non-Faradaic enhancement of N2O decomposition was observed at cathodic overpotentials, and |Λ| values above unity were achieved. Electroche...

The current paper concerns the simulation of biomass pyrolysis conjunction to SOFCs, in an integrated process for the simultaneous production electrical/thermal power and phenols. The version of the conjunction of the two processes under study involved the gasification of the remaining biofuel (after the separation of the phenols fraction) and the...

A series of metal catalysts (Pd, Rh, Ru, Cu, Fe, In and Ni) supported on γ-Al2O3 carrier, were evaluated during N2O catalytic conversion to N2 in the absence and presence of excess oxygen and reducing agents (CH4 or C3H8). Among all catalysts tested, Pd-, Ru- and Rh-based samples exhibited the best catalytic performance, in all reaction conditions...

The present study aims at exploring the surface and catalytic behavior of Rh/gamma-Al(2)O(3) catalysts during the selective reduction of NO by C(3)H(8) in the presence of excess oxygen, H(2)O, and SO(2) with particular emphasis on identifying the elementary steps that describe the reaction mechanism. To this end, detailed activity and stability tes...

The effect of the pretreatment (inert, oxidative, and reducing) of Ru/γ-Al2O3 catalyst on its activity and stability in the decomposition of N2O in the absence or presence of O2, SO2, H2O and NOX was studied in the present work. Decomposition of pure N2O was slightly enhanced by the H2-pretreated catalyst (metallic Ru) compared to the O2- or He-pre...

The integration of solid oxide fuel cells (SOFCs) in biomass gasification–turbine processes was studied for the estimation of the overall electrical efficiency. Since both processes operate close to 1000 °C, heat integration is one of the benefits of the proposed scheme. Heat generated at the SOFC and the afterburner of the integrated process was f...

The reaction of NH3 decomposition was studied on Ag in a proton conducting double chamber cell-reactor. The proton conductor was a strontia-ceria-ytterbia (SCY) perovskite of the form SrCe0.95Yb 0.05O3-α. The reaction was studied at 350-700 °C and atmospheric total pressure. The proton transference number (PTN) was calculated by simultaneous measur...

The never-ending stories on an alternative energy supply for a cleaner environment, recently related with efforts to decrease global CO2 emissions, has been revived by the steep increase in oil prices (over 100$/barrel) and the parallel controversy about the potential and public acceptance of nuclear energy. Thus, it is now the right time for the s...

In the present work, a three dimensional model examining the fluid flow along with the fundamental transport phenomena occurring in a typical polymer electrolyte fuel cell (PEMFC), i.e. heat transfer, mass transport and charge transfer, has been developed. The flow field was simulated according to the well known Navier-Stokes equations, while the h...

In the present work, the prospects and trends of solid electrolyte membrane reactors (SEMRs) towards hydrogen production, are discussed. Initially, an overview of the principles, the properties and the techniques related to the usage of the SEMRs, are presented. In the following, a literature survey covering earlier and recent developments of the v...

The (electro-)kinetics of the reverse water gas shift (RWGS) reaction was studied in a solid oxide fuel cell (SOFC) of the type Pt/YSZ/Pt. The effect of imposed potentials, cell temperature (650–800°C), H2 (1–10kPa) and CO2 (1–10kPa) partial pressures on the kinetics and mechanism of the catalytic and electrocatalytic RWGS reaction, were systematic...

The (electro-)kinetics of the reverse water gas shift (RWGS) reaction was studied in a solid oxide fuel cell (SOFC) of the type Pt/YSZ/Pt. The effect of imposed potentials, cell temperature (650–800 8C), H 2 (1–10 kPa) and CO 2 (1–10 kPa) partial pressures on the kinetics and mechanism of the catalytic and electrocatalytic RWGS reaction, were syste...

The effect of hydrogen partial pressure (1.3–5.8 kPa) and cell temperature (600–800 °C) on the kinetics and mechanism of the charge transfer electrode reaction taking place at the three phase boundary H2–Fe–SCY (SCY = SrCe0.95Yb0.05O2.975), was thoroughly examined by performing electrode polarization measurements. A three electrode single chamber p...

In this paper the integrated process of biomass gasification and a solid oxide fuel cell (SOFC) was studied in terms of thermodynamics. The study is based on an ongoing project intending to develop an innovative sustainable technology with high efficiency. According to some assumptions, the energy balance revealed that the process can be auto-therm...

Electrode polarization and conductivity measurements were carried out at the Pd/YSZ interface and at conditions close to the Pd–PdO thermodynamic equilibrium. The steady-state current–overpotential characteristics were analyzed with a Butler–Volmer type of equation. Both, apparent exchange current density, Io, and anodic/cathodic charge transfer co...

Detailed kinetic studies are presented for two reactions: the nitric oxide (NO) selective catalytic reduction (SCR) by propene over indium/alumina (In/Al2O3) and the nitrous oxide (N2O) reduction over ruthenium/alumina (Ru/Al2O3). Both reactions were studied in the presence of excess oxygen (O2) to simulate the composition of flue gases. Apparent a...

The simultaneous catalytic reduction of both NOX and N2O in excess O2 using propene as the reductant was studied in the absence and in the presence of 10% H2O and 50 ppm SO2. Reduction took place in a dual-bed catalytic reactor consisting of In/Al2O3 in the upper layer and of Ru/Al2O3 in the lower one. The effect of SO2 and/or H2O on the NOX and N2...

Mechanistic and kinetic experiments were carried out on the NOX selective catalytic reduction (SCR) by C3H6 in excess O2 over In/Al2O3 in the presence and absence of SO2 and H2O. The In loadings in the catalyst varied in the range of 1–4%. The 2% In/Al2O3 exhibited the highest activity. The performance of the aforementioned catalyst was measured us...

Catalyst evaluation and kinetic analysis was performed on the catalytic decomposition of N2O to N2 over a Ru/Al2O3. An oxygen rich feed containing SO2 and H2O were used in order to examine their influence on the catalyst activity. An Al2O3 support was used with various Ru loadings (1–4%). No enhancement in the activity was observed for Ru loadings...

The simultaneous reduction of N2O+NO with carbon supported Ni/K catalysts was studied. High conversions of both compounds were obtained at 400°C, and a synergystic effect between Ni and K was observed.

The catalytic oxidation of carbon monoxide on Fe catalyst was studied at 300–500 °C and atmospheric total pressure. The reaction was studied under both open- and closed-circuit operation in an yttria-stabilized zirconia solid electrolyte cell. The technique of Solid Electrolyte Potentiometry (SEP) was used to monitor the thermodynamic activity of o...

HACCP (Hazard Analysis Critical Control Point)has been internationally recognized as a logical tool towards a more modern, scientifically based inspection system. The main sector where HACCP finds application is in the processing of safe food. The influence of the application of the HACCP system in Greek industry was examined as a function of impor...

HACCP (Hazard Analysis Critical Control Point) has been internationally recognized as a logical tool towards a more modern, scientifically based inspection system. The main sector where HACCP finds application is in the processing of safe food. The influence of the application of the HACCP system in Creek industry was examined as a function of impo...

Ammonia was synthesized from its elements at atmospheric pressure in a solid state proton (H+)-conducting cell-reactor. Hydrogen was flowing over the anode and was converted into protons that were transported through the solid electrolyte and reached the cathode (palladium) over which nitrogen was passing. At 570 degreesC and atmospheric pressure,...