Effect of fuel thermal pretreament on the electrochemical performance of a direct lignite coal fuel cell

Proceedings of the 20th International Conference on Solid State Ionics SSI-20The impact of fuel heat pretreatment on the performance of a direct carbon fuel cell (DCFC) is investigated by utilizing lignite (LG) coal as feedstock in a solid oxide fuel cell of the type: lignite | Co–CeO2/YSZ/Ag | air. Four LG samples are employed as feedstock: (i) pristine lignite (LG), and differently heat treated LG samples under inert (He) atmosphere at (ii) 200 °C overnight (LG200), (iii) 500 °C for 1 h (LG500) and (iv) 800 °C for 1 h (LG800). The impact of several process parameters, related to cell temperature (700–800 °C), carrier gas type (He or CO2), and molten carbonate infusion into the feedstock on the DCFC performance is additionally explored. The proximate and ultimate analysis of the original and pretreated lignite samples show that upon increasing the heat treatment temperature the carbon content is monotonically increased, whereas the volatile matter, moisture, sulfur and oxygen contents are decreased. In addition, although volatiles are eliminated upon increasing the treatment temperature and as a consequence more ordered carbonaceous structure remained, the heat treatment increases the reactivity of lignite with CO2 due mainly to the increased carbon content. These modifications are reflected on the achieved DCFC performance, which is clearly improved upon increasing the treatment temperature. An inferior cell performance is demonstrated by utilizing inert He instead of reactive CO2 atmosphere, as purging gas in the anode compartment, while carbonate infusion always results in ca. 70–100% increase in power output (15.1 mW cm− 2 at 800 °C). The obtained findings are discussed based also on AC impedance spectroscopy measurements, which revealed the impact of LG physicochemical characteristics and DCFC operating parameters on both ohmic and electrode resistances.The authors would like to acknowledge financial support from the European project “Efficient Conversion of Coal to Electricity — Direct Coal Fuel Cells”, which is funded by the Research Fund for Carbon & Steel (RFCR CT-2011-00004).Peer reviewe

Direct utilization of lignite coal in a Co–CeO2/YSZ/Ag solid oxide fuel cell

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 °C), carrier gas composition (CO2/He mixtures), and total feed flow rate (10–70 cm3/min), was systematically examined. The effect of molten carbonates on DCFC performance was also investigated by employing a eutectic mixture of lithium and potassium carbonates as carbon additives. In the absence of carbonates, the optimum performance (∼10 mW cm−2 at 800 °C), was achieved by employing 20 wt.% Co/CeO2 as anodic electrode and pure CO2 as purging gas. An inferior behavior was demonstrated by utilizing He instead of CO2 atmosphere in anode compartment and by increasing purging gas flow rate. Carbonates infusion into lignite feedstock resulted in a further increase of maximum power density up to 32%. The obtained findings are discussed based also on AC impedance spectroscopy measurements, which revealed the impact of DCFC operating parameters on both ohmic and electrode resistances.The authors would like to acknowledge financial support from the European project “Efficient Conversion of Coal to Electricity – Direct Coal Fuel Cells”, which is funded by the Research Fund for Carbon & Steel (RFCR-CT-2011-00004). In addition the authors are grateful to Prof. V. Stathopoulos and Mr. P. Pandis for conducting the Direct Current Four Point (DC4P) measurements.Peer reviewe

Ethanol/water mixture permeation behavior through membrane electrode assembly (MEA) in PEMFC

Direct ethanol fuel cells (DEFCs) have been paid more and more attention in recent years due to the following advantages of ethanol: low toxicity, renewability and easy production by the fermentation of agricultural products [1]. Based on the present status of the electrolyte development, Naifon® membrane series is the most commonly used. It is well known that its conductivity is dependent on the water content in the membrane in a more a less linear fashion [2]. This necessitates sufficient water in the polymer electrolyte. On the other hand, water content can not be so high that the electrode will be flooded. Proper management of water through the membrane is indispensable for the desirable cell performance. Furthermore, ethanol can also permeate across Nafion® membranes, leading to a mixed potential and catalyst poison at the cathode, consequently causing the decreased cell performance and fuel utilization [3]. These both issues make it necessary to investigate the ethanol/water permeation behavior through membrane electrode assembly in PEMFCs. In the present work, water and ethanol crossover rates through membrane electrode assembly (MEA) were determined in a polymer electrolyte fuel cell (PEMFC). The investigated MEA consisted of two Pt/C electrodes (40 wt. %) and a Nafion®-115 membrane as the electrolyte. The anode compartment was pumped by ethanol aqueous solutions with different concentrations, and the cathode was supplied with high-purity helium at different flow rates to sweep off the permeated ethanol and water. The effluent from the cathode was on-line determined by gas Chromatograph (GC-14B, Shimadzu). The effect of the operation parameters such as the cell temperature, the carrier gas (He) flowrate at the cathode and the concentration of ethanol aqueous solutions on the ethanol/water permeation behavior was investigated. Based on the experimental results, it was found that the crossover rates of both water and ethanol increase with the increment of the operation temperature and the carrier gas (He) flow rate at the cathode. It was also found that the ethanol concentration had a significant effect on the crossover rates of ethanol and water. In the case of ethanol, the permeation rates presented a volcano behavior as the ethanol concentration increased, reaching a peak value when the ethanol concentration was 6.0 mol/L, which could be attributable to the different swelling behavior of Nafion® membrane in different ethanol aqueous solutions

The synergistic catalyst-carbonates effect on the direct bituminous coal fuel cell performance

The current work explores the feasibility to improve the performance of a Direct Carbon Fuel Cell (DCFC): CO2 + bituminous coal|Co-CeO2/YSZ/Ag|Air by infusing a gasification catalyst (Co/CeO2) and/or Li-K carbonates mixture into the carbon fuel. The different fuel feedstock mixtures were characterized by various methods, involving chemical composition and proximate analysis, particle size distribution (PSD), X-ray diffraction (XRD), N2 adsorption-desorption (BET method), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM), to gain insight into the effect of catalyst and/or carbonates addition to fuel mixture physicochemical characteristics. An increase of the power output up to ca. 20 and 80% is achieved for carbon/catalyst and carbon/catalyst/carbonates mixtures, respectively, in comparison to bare carbon at 700 °C, demonstrating the pronounced effect of catalyst as well as its potential synergy with carbonates. It was also shown that the achieved maximum power density is directly associated with the CO formation rate, implying the importance of in situ formed CO on the electrochemical performance. The obtained findings are further discussed based also on the corresponding AC impedance spectroscopy studies, which revealed the beneficial effect of fuel feedstock additives (catalyst and/or carbonates) on ohmic and electrode polarization resistances. The present results clearly revealed the feasibility to improve the DCFC performance by concurrently infusing a gasification catalyst and carbonates mixture into fuel feedstock.This research has been co-financed by the European Union and Greek national funds through the Operational Program Competitiveness, Entrepreneurship and Innovation, under the call RESEARCH – CREATE – INNOVATE (project code: T1EDK-01894). Dr. Kaklidis' postdoctoral research was realized via the framework of “Grant Allowance for Post-Doctoral Researchers” of the operational programme “Human Resources Development, Education and Lifelong Learning”, 2014–2020, implemented by the State Scholarships Foundation (ΙΚΥ) and co-funded by the European Social Fund and the Hellenic state.Peer reviewe

The combined impact of carbon type and catalyst-aided gasification process on the performance of a Direct Carbon Solid Oxide Fuel Cell

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 °C) and catalyst (Co/CeO2) infusion to carbon feedstock under CO2 atmosphere at the anode chamber is systematically investigated in a cell of the type: Carbon + CO2|Cu-CeO2/YSZ/Ag|Air. All fuel samples were characterized, in terms of chemical composition, crystallite structure (XRD), pore structure (BET), surface morphology (SEM), particle size distribution (PSD) and thermogravimetric analysis (TGA), in order to obtain a close relationship between the carbon characteristics and the DCFC performance. The results reveal that in the absence of catalyst, the optimum performance is obtained for the charcoal sample (Pmax ~ 12 mW/cm2), due to its high volatile matter, oxygen content, porosity and carbon disorder as well as its low amount of impurities. Catalyst infusion to carbon feedstock results in a considerable increase in the achieved cell power density up to 225%, which is more pronounced for the less reactive coals and low temperatures. The enhanced performance obtained by infusing Co/CeO2 catalyst into carbon is ascribed to the positive effect of catalyst on the in situ carbon gasification, through the reverse Boudouard reaction (C + CO2 → 2CO), and the subsequent faster diffusion and electro-oxidation of formed CO at the anodic three-phase boundary.The authors would like to acknowledge financial support from the ERANET-MED (call identifier RQ2-2016) project “Direct Conversion of Biomass to Electricity in MED area via an Internal Catalytic Gasification Solid Oxide Fuel Cell”, which is co-funded by the following Euro-Mediterranean countries: Algeria, Cyprus, Egypt, France, Germany, Greece, Italy, Jordan, Lebanon, Malta, Morocco, Spain, Tunisia, Turkey (ERANETMED2-72-246 DB-SOFC).Peer reviewe

Direct utilization of lignite coal in CoCeO2/YSZ/Ag solid oxide fuel cell

Summarization: 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 °C), carrier gas composition (CO2/He mixtures), and total feed flow rate (10–70 cm3/min), was systematically examined. The effect of molten carbonates on DCFC performance was also investigated by employing a eutectic mixture of lithium and potassium carbonates as carbon additives. In the absence of carbonates, the optimum performance (∼10 mW cm−2 at 800 °C), was achieved by employing 20 wt.% Co/CeO2 as anodic electrode and pure CO2 as purging gas. An inferior behavior was demonstrated by utilizing He instead of CO2 atmosphere in anode compartment and by increasing purging gas flow rate. Carbonates infusion into lignite feedstock resulted in a further increase of maximum power density up to 32%. The obtained findings are discussed based also on AC impedance spectroscopy measurements, which revealed the impact of DCFC operating parameters on both ohmic and electrode resistances.Παρουσιάστηκε στο: 13th International Conference on Clean Energ

Insights into the role of SO2 and H2O on the surface characteristics and de-N2O efficiency of Pd/Al2O3 catalysts during N2O decomposition in the presence of CH4 and O2 excess

Summarization: The catalytic abatement of nitrous oxide (N2O), a powerful greenhouse and ozone depletion gas, is an efficient end-of-pipe technology for N2O emissions control. However, de-N2O performance is notably suppressed by SO2 and H2O presence on the flue gases, whereas little is known about their influence on catalyst surface chemistry. In the present study, the impact of sulfur dioxide and water vapor on the catalytic performance of Pd/Al2O3 catalysts during the N2O decomposition in the presence of CH4 and O2 excess is investigated, with particular emphasis on the corresponding surface chemistry modifications. Catalytic activity and stability measurements, in conjunction with a kinetic study, were carried out to elucidate the individual effect of each molecule on de-N2O performance. X-ray photoelectron spectroscopy (XPS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and Fourier transform infrared spectroscopy (FTIR) of pyridine adsorption are employed to evaluate the impact of SO2 and H2O molecules on catalyst surface chemistry, which is appropriately correlated with the achieved catalytic performance. The results revealed that the de-N2O efficiency can be substantially improved by CH4 under reducing (absence of O2) conditions, due to the scavenging of strongly adsorbed Oads species by the hydrocarbon; however, under O2 excess conditions the beneficial effect of CH4 is marginal. Water vapor in the feed has a detrimental influence on both N2O and CH4 conversions, which, however, is totally reversible; the latter is mainly ascribed to the competitive adsorption of H2O molecules on catalyst surface. In contrast, SO2 addition in feed stream results in a severe, irreversible deactivation; SO2 leads to the creation of Brönsted acid sites on Al2O3 support, which in turn results in highly oxidized Pd entities, inactive for N2O decomposition.Presented on: Applied Catalysis B: Environmenta