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Fuel cells and electrochemical reactors

ProboStat with suitable gas mixer can be used to test and characterize button fuel cells, tubular metal-supported SOFC and SOEC and run electrochemical reactors. The electrical analysis may for such applications be accompanied by analysis of gas compositions at the outlets.

While tubular constructs do not offer the same power density as planar stacks, they may be more robust for certain demonstration and research projects and – perhaps most importantly – have cold seals. The ProboStat is suitable for running one such tube.

 

These articles refer to ProboStat or other NorECs products, filtered with keywords: 'Fuel cell, Fuelcell, SOFC'  
ID=394

Magnetron-sputtered La0.6Sr0.4Co0.2Fe0.8O3 nanocomposite interlayer for solid oxide fuel cells

Authors A. A. Solovyev, I. V. Ionov, A. V. Shipilova, A. N. Kovalchuk, M. S. Syrtanov
Source
Journal of Nanoparticle Research
Time of Publication: 2017
Abstract A thin layer of a La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) is deposited between the electrolyte and the La0.6Sr0.4Co0.2Fe0.8O3/Ce0.9Gd0.1O2 (LSCF/CGO) cathode layer of a solid oxide fuel cell (SOFC) by pulsed magnetron sputtering using an oxide target of LSCF. The films were completely dense and well adherent to the substrate. The effects of annealing in temperature range from 200 to 1000 C on the crystalline structure of the LSCF films have been studied. The films of nominal thickness, 250–500 nm, are crystalline when annealed at temperatures above 600 C. The crystalline structure, surface topology, and morphology of the films were determined using X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM), respectively. To study the electrochemical characteristics of the deposited-film, solid oxide fuel cells using 325-nm LSCF films as interlayer between the electrolyte and the cathode have been fabricated. The LSCF interlayer improves the overall performance of the SOFC by increasing the interfacial area between the electrolyte and cathode. The electrolyte-supported cells with the interlayer have 30% greater, overall power output compared to that achieved with the cells without interlayer. The LSCF interlayer could also act as a transition layer that improves adhesion and relieves both thermal stress and lattice strain between the cathode and the electrolyte. Our results demonstrate that pulsed magnetron sputtering provides a low-temperature synthesis route for realizing ultrathin nanocrystalline LSCF film layers for intermediate- or low-temperature solid oxide fuel cells.
Keywords (La,Sr)(Co,Fe)O3 Magnetron sputtering Nanocomposite Interlayer Solid oxide fuel cells Nanostructured thin films Energy conversion
Remark DOI: 10.1007/s11051-017-3791-0
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ID=392

Status report on high temperature fuel cells in Poland – Recent advances and achievements

Authors J. Molenda, J. Kupecki, R. Baron, M. Blesznowski, G. Brus, T. Brylewski, M. Bucko, J. Chmielowiec, K. Cwieka, M. Gazda, A. Gil, P. Jasinski, Z. Jaworski, J. Karczewski, M. Kawalec, R. Kluczowski, M. Krauz, F. Krok, B. Lukasik, M. Malys, A. Mazur, A. Miele
Source
International Journal of Hydrogen Energy
Volume: 42, Issue: 7, Pages: 4366–4403
Time of Publication: 2017
Abstract The paper presents recent advances in Poland in the field of high temperature fuel cells. The achievements in the materials development, manufacturing of advanced cells, new fabrication techniques, modified electrodes and electrolytes and applications are presented. The work of the Polish teams active in the field of solid oxide fuel cells (SOFC) and molten carbonate fuel cell (MCFC) is presented and discussed. The review is oriented towards presenting key achievements in the technology at the scale from microstructure up to a complete power system based on electrochemical fuel oxidation. National efforts are covering wide range of aspects both in the fundamental research and the applied research. The review present the areas of (i) novel materials for SOFC including ZrO2-based electrolytes, CeO2-based electrolytes, Bi2O3 based electrolytes and proton conducting electrolytes, (ii) cathode materials including thermal shock resistant composite cathode material and silver-containing composites, (iii) anode materials, (iv) metallic interconnects for SOFC, (v) novel fabrication techniques, (vi) pilot scale SOFC, including electrolyte supported SOFC (ES-SOFC) and anode supported SOFC (AS-SOFC), (vii) metallic supported SOFC (MS-SOFC), (viii) direct carbon SOFC (DC-SOFC), (ix) selected application of SOFC, (x) advances in MCFC and their applications, (xi) advances in numerical methods for simulation and optimization of electrochemical systems.
Keywords SOFC; MCFC; Experiments; Simulations; Fabrication techniques
Remark https://doi.org/10.1016/j.ijhydene.2016.12.087
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ID=388

Co- and Ce/Co-coated ferritic stainless steel as interconnect material for Intermediate Temperature Solid Oxide Fuel Cells

Authors Hannes Falk-Windisch, , Julien Claquesin, Mohammad Sattari, Jan-Erik Svensson, Jan Froitzheim
Source
Journal of Power Sources
Volume: 343, Pages: 1-10
Time of Publication: 2017
Abstract Chromium species volatilization, oxide scale growth, and electrical scale resistance were studied at 650 and 750 C for thin metallic Co- and Ce/Co-coated steels intended to be utilized as the interconnect material in Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFC). Mass gain was recorded to follow oxidation kinetics, chromium evaporation was measured using the denuder technique and Area Specific Resistance (ASR) measurements were carried out on 500 h pre-exposed samples. The microstructure of thermally grown oxide scales was characterized using Scanning Electron Microscopy (SEM), Scanning Transmission Electron Microscopy (STEM), and Energy Dispersive X-Ray Analysis (EDX). The findings of this study show that a decrease in temperature not only leads to thinner oxide scales and less Cr vaporization but also to a significant change in the chemical composition of the oxide scale. Very low ASR values (below 10 mΩ cm2) were measured for both Co- and Ce/Co-coated steel at 650 and 750 C, indicating that the observed change in the chemical composition of the Co spinel does not have any noticeable influence on the ASR. Instead it is suggested that the Cr2O3 scale is expected to be the main contributor to the ASR, even at temperatures as low as 650 C.
Keywords Interconnect; Solid oxide fuel cell; Corrosion; Cr vaporization; Area specific resistance; Coating
Remark http://dx.doi.org/10.1016/j.jpowsour.2017.01.045
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ID=387

Characterization of laser-processed thin ceramic membranes for electrolyte-supported solid oxide fuel cells

Authors J.A. Cebollero, R. Lahoz, M.A. Laguna-Bercero, J.I. Pea, A. Larrea, V.M. Orera
Source
International Journal of Hydrogen Energy
Time of Publication: 2017
Abstract By laser machining we have prepared thin and self-supported yttria stabilized zirconia (YSZ) electrolytes that can be used in electrolyte-supported solid oxide fuel cells for reducing the operation temperature. The membranes, which are supported by thicker areas of the same material, have an active area of ∼20 μm in thickness and up to 8 mm in diameter. Buckling limits the maximum size of the thin areas to below 1 mm, the overall effective active area being formed by multiple thin areas bounded by ribs. Electron Backscattering Diffraction experiments determined that there are not significant strains inside the membranes and that the heat-affected zone is confined to a shallow layer of ∼1–2 μm. The bending strength of the membranes decreases by ∼26% as a result of the surface microcracking produced by the laser machining. The membranes have a roughness of ∼2.5 μm and are coated by a layer of nanoparticles produced by the laser ablation. This coating and small roughness is not detrimental for the cathodic polarization of the cells. Conversely, the cathode polarization resistance decreases ∼5% in the 650–850 C temperature range.
Keywords SOFC; Solid electrolytes; Laser machining; Self-supporting ceramic membranes
Remark http://dx.doi.org/10.1016/j.ijhydene.2016.12.112
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ID=385

The structural and electrical properties of samarium doped ceria films formed by e-beam deposition technique

Authors Darius Virbukas, Giedrius Laukaitis
Source
Solid State Ionics
Time of Publication: 2016
Abstract Sm2O3-doped CeO2 (Sm0.15Ce0.85O1.925, SDC) thin films were formed by e-beam evaporation method. Thin films were formed evaporating micro powders (particle size varied from 0.3 to 0.5 μm). The influence of deposition rate on formed thin film structures and surface morphology were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersion spectrometry (EDS), and atomic force microscopy (AFM). The deposition rate of formed SDC thin films was changed from 2 to 16 /s. The electrical properties were investigated as a function of frequency (0.1–106 Hz) at different temperatures (473–873 K). The formed SDC thin ceramic films repeat the crystallographic orientation of the initial powders using different substrates and different deposition rate. It was determined that crystallites size and samarium concentration are decreasing by increasing the deposition rate. The crystallites size decreased from 17.0 nm to 10.4 nm when SDC thin films were deposited on Alloy 600 (Fe-Ni-Cr), and decreased from 13.7 nm to 8.9 nm when were used optical quartz substrate. The best ionic conductivity σtot = 1.66 Sm− 1 at 873 K temperature, activation energy ΔEa = 0.87 eV (σg = 1.66 Sm− 1, σgb = 1.66 Sm− 1) was achieved when 2 /s deposition rate was used. The grain size (in the formed SDC thin films) was ~ 83 nm in this case.
Keywords Electron beam deposition; Samarium doped ceria oxide (SDC); Solid oxide fuel cells (SOFC); Ionic conductivity
Remark http://dx.doi.org/10.1016/j.ssi.2016.12.003
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ID=374

Evaluation of La0.75Sr0.25Cr0.5Mn0.5O3 protective coating on ferritic stainless steel interconnect for SOFC application

Authors R.K. Lenka, P.K. Patro, Jyothi Sharma, T. Mahata, P.K. Sinha
Source
International Journal of Hydrogen Energy
Time of Publication: 2016
Abstract Ferritic stainless steel (SS) interconnect used for intermediate temperature solid oxide fuel cell has issues associated with the growth of oxide scale on the surface and evaporation of chromium species to the cathode leading to increase in polarization resistance and hence, overall cell resistance. Protective coating is essentially applied over the SS surface to restrict the above phenomena. In the present investigation, strontium doped lanthanum manganese chromite (LSCM) of composition La0.75Sr0.25Cr0.5Mn0.5O3 has been explored as a possible protective coating material on ferritic SS interconnect surface. For this application, fine LSCM powder was synthesized by solution polymerization method. Terpineol based slurry of LSCM was formulated and used for coating on ferritic SS surface by screen printing. LSCM coated ferritic SS was exposed to moist oxygen at 800 C for 300 h and area specific resistance (ASR) of the coating was found to be as low as 2.0 mΩ cm2 after exposure. Microstructure of LSCM coating and the chromium oxide film was investigated using SEM and EDS. The results indicate that LSCM can form an effective protective coating on ferritic stainless steel for SOFC interconnect application.
Keywords Interconnect; Protective coating; LSCM; SOFC
Remark http://dx.doi.org/10.1016/j.ijhydene.2016.08.143
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ID=373

Solid oxide carbonate composite fuel cells: Size effect on percolation

Authors Shalima Shawuti, , Mehmet Ali Glgn
Source
International Journal of Hydrogen Energy
Time of Publication: 2016
Abstract In the studies of solid oxide carbonate composite fuel cell, percolation behaviour of the two phases was investigated as a function of particle size of the oxide phase. The ratio of amount of samarium doped ceria (SDC; Sm0.2Ce0.8O) to Na2CO3 was varied to determine an optimum ionic conductivity as function of oxide particle size. The roles of both phases in the composite electrolyte were investigated. SDC particles were mixed in different amounts of Na2CO3 to obtain composites with carbonate ratios from 1 wt% to 50 wt%. Micro-structural investigations showed that Na2CO3 phase served as the matrix in the micro-structure gluing the oxide particles together. The lowest and the highest carbonate ratios caused low conductivities in the composite as in these samples the 3D connectivity of both phases were disrupted. Low conductivity at both ends of the mixture composition could be interpreted as none of the components of the composite dominated the ionic conductivity. The highest conductivity was obtained at 10 wt% Na2CO3 amount in the composite electrolyte when nano-sized SDC (5–10 nm) oxide powders were used. Two different particle sizes of SDC powders were used to show that the optimum phase ratio, i.e. percolation of both phases, is function of particle size as well. The conductivity in the composite showed percolation behaviour with respect to the two constituent phases.
Keywords Composite electrolyte; SOFC; Interface; Percolation; Carbonate; Impedance
Remark http://dx.doi.org/10.1016/j.ijhydene.2016.07.208, in press
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ID=365

Leaching effect in gadolinia-doped ceria aqueous suspensions for ceramic processes

Authors A. Caldarelli, E. Mercadelli, S. Presto, M. Viviani, A. Sanson
Source
Journal of Power Sources
Volume: 326, Issue: 15, Pages: 70–77
Time of Publication: 2016
Abstract Gadolinium doped ceria (CGO) is a commonly used electrolytic material for Solid Oxide Fuel Cells (SOFCs) and for this reason different shaping methods for its deposition are reported in literature. Most of these processes are based on the use of organic-based CGO suspensions, but water-based processes are acquiring increasingly interest for their economical and environmental friendly properties. In this paper we reported how the components of water-based suspension and some unexpected process parameters can deeply affect the functional properties of the final powder. In particular, we observed that CGO powders are strongly affected by ionic leaching induced by furoic acid used as dispersant: the extent of this leaching was related to the dispersant concentration and suspension’s ball-milling-time; the phenomenon was confirmed by ICP-AES analyses on suspensions surnatant. Most importantly, ionic leaching affected the electrical properties of CGO: leached powder showed a higher ionic conductivity as a consequence of a partial removal of Gd ions at the grain boundaries. This work is therefore pointing out that when considering water-based suspensions, it is extremely important to carefully consider all the process parameters, including the organic components of the ceramic suspension, as these could lead to unexpected effects on the properties of the powder, affecting the performance of the final shaped material.
Keywords Gadolinium doped ceria; Water-based suspensions; Furoic acid; Ionic leaching; Electrical conductivity
Remark doi:10.1016/j.jpowsour.2016.06.069
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ID=361

Synthesis, characterization and performance of robust poison-resistant ultrathin film yttria stabilized zirconia – nickel anodes for application in solid electrolyte fuel cells

Authors F.J. Garcia-Garcia, F. Yubero, J.P. Espins, A.R. Gonzlez-Elipe, R.M. Lambert
Source
Journal of Power Sources
Volume: 324, Pages: 679–686
Time of Publication: 2016
Abstract We report on the synthesis of undoped ∼5 μm YSZ-Ni porous thin films prepared by reactive pulsed DC magnetron sputtering at an oblique angle of incidence. Pre-calcination of the amorphous unmodified precursor layers followed by reduction produces a film consisting of uniformly distributed tilted columnar aggregates having extensive three-phase boundaries and favorable gas diffusion characteristics. Similarly prepared films doped with 1.2 at.% Au are also porous and contain highly dispersed gold present as Ni-Au alloy particles whose surfaces are strongly enriched with Au. With hydrogen as fuel, the performance of the undoped thin film anodes is comparable to that of 10–20 times thicker typical commercial anodes. With a 1:1 steam/carbon feed, the un-doped anode cell current rapidly falls to zero after 60 h. In striking contrast, the initial performance of the Au-doped anode is much higher and remains unaffected after 170 h. Under deliberately harsh conditions the performance of the Au-doped anodes decreases progressively, almost certainly due to carbon deposition. Even so, the cell maintains some activity after 3 days operation in dramatic contrast with the un-doped anode, which stops working after only three hours of use. The implications and possible practical application of these findings are discussed.
Keywords Magnetron sputtering; Oblique angle deposition; Thin film anodes; Carbon-tolerant; SOFC
Remark doi:10.1016/j.jpowsour.2016.05.124
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ID=357

Effect of Nd-deficiency on electrochemical properties of NdBaCo2O6−δ cathode for intermediate-temperature solid oxide fuel cells

Authors Kaihua Yia,Liping Sun, Qiang Li, Tian Xia, Lihua Huo, Hui Zhao, Jingwei Li, Zhe L, Jean-Marc Bassat, Aline Rougier, Sbastien Fourcade, Jean-Claude Grenier
Source
International Journal of Hydrogen Energy
Volume: 41, Issue: 24, Pages: 10228–10238
Time of Publication: 2016
Abstract Nd1−xBaCo2O6−δ (N1−xBCO) is evaluated as cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The effects of Nd-deficiency on the crystal structure, thermal expansion behavior, electrical conductivity and electrochemical performance are studied. N1−xBCO oxides crystallize in the orthorhombic symmetry with Pmmm space group. A good chemical compatibility between N1−xBCO and CGO electrolyte is found at 1100 C in air. Introducing Nd-deficiency promotes the formation of oxygen vacancy, and significantly improves the electrochemical performance of N1−xBCO cathodes. The lowest area specific resistance (ASR) value of 0.043 Ω cm2 is obtained on the N0.96BCO cathode at 700 C in air. The rate limiting step for electrochemical oxygen reduction reaction (ORR) is charge transfer process at the interface. The power output of the electrolyte supported cell Ni-CGO/CGO/N0.96BCO reaches 0.6 W cm−2 at 700 C.
Keywords Solid oxide fuel cell; Double perovskite; Nd-deficiency; Cathode; Electrode reaction
Remark doi:10.1016/j.ijhydene.2016.04.248
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ID=355

Influence of cathode functional layer composition on electrochemical performance of solid oxide fuel cells

Authors Antnio de Pdua Lima Fernandes, Eric Marsalha Garcia, Rubens Moreira de Almeida, Hosane Aparecida Taroco, Edyth Priscilla Campos Silva, Rosana Zacarias Domingues, Tulio Matencio
Source
Journal of Solid State Electrochemistry
Time of Publication: 2016
Abstract In this work, anode-supported solid oxide fuel cells (SOFC) were tested with a yttria-stabilized zirconia (YSZ) (8 mol% Y2O3-ZrO2)/gadolinium-doped ceria (GDC) (Ce0.9Gd 0.1O1.95) bilayer electrolyte and two lanthanum strontium cobalt ferrite (LSCF) composition as functional cathode layer: La0.6Sr0.4Co0.8Fe0.2O3-δ (LSCF 1) and La0.60Sr0.40Co0.2Fe0.8O3-δ (LSCF 2). The functional cathode layers were made of 50 % (w/w) LSCF and 50 % (w/w) GDC. Microstructural characterization was performed by scanning electron microscopy and X-ray diffraction. Electrochemical impedance spectroscopy (EIS) and power measurements were performed under oxygen and hydrogen atmospheres. The microscopy studies showed that the LSCF 2 functional layer is more uniform and adherent to the electrolyte and the cathode collector than the LSCF 1 functional layer, which has cracks, chips, and lower adhesion. The use of the LSCF 2 layer allowed an approximately 25-fold reduction in ohmic resistance (0.06 Ω cm−2) compared with the LSCF 1 layer (1.5 Ω cm−2). The power measurements showed a considerable increase in the power cell using LSCF 2 (approximately 420 mW cm−2) compared with the power cell using LSCF 1 (approximately 180 mW cm−2).
Keywords SOFC, LSCF, Interface, Electrochemical performance, Cathode, Functional layer
Remark First Online: 20 May 2016. DOI: 10.1007/s10008-016-3241-4
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ID=353

Electrochemical Property Assessment of Pr2CuO4 Submicrofiber Cathode for Intermediate-Temperature Solid Oxide Fuel Cells

Authors Ting Zhao, Li-Ping Sun, Qiang Li, Li-Hua Huo, Hui Zhao, Jean-Marc Bassat, Aline Rougier, Sbastien Fourcade and Jean-Claude Grenier
Source
Journal of Electrochemical Energy Conversion and Storage
Volume: 13, Issue: 1, Pages: 011006
Time of Publication: 2016
Abstract The Pr2CuO4 (PCO) submicrofiber precursors are prepared by electrospinning technique and the thermo-decomposition procedures are characterized by thermal gravity (TG), X-ray diffraction (XRD), Fourier transform infrared spectoscopy (FT-IR), and scanning electron microscopy (SEM), respectively. The fibrous PCO material was formed by sintering the precursors at 900 C for 5 hrs. The highly porous PCO submicrofiber cathode forms good contact with the Ce0.9Gd0.1O1.95 (CGO) electrolyte after heat-treated at 900 C for 2 hrs. The performance of PCO submicrofiber cathode is comparably studied with the powder counterpart at various temperatures. The porous microstructure of the submicrofiber cathode effectively increases the three-phase boundary (TPB), which promotes the surface oxygen diffusion and/or adsorption process on the cathode. The PCO submicrofiber cathode exhibits an area specific resistance (ASR) of 0.38 Ω cm2 at 700 C in air, which is 30% less than the PCO powder cathode. The charge transfer process is the rate limiting step of the oxygen reduction reaction (ORR) on the submicrofiber cathode. The maximum power densities of the electrolyte-support single cell PCO|CGO|NiO-CGO reach 149 and 74.5 mW cm−2 at 800 and 700 C, respectively. The preliminary results indicate that the PCO submicrofiber can be considered as potential cathode for intermediate temperature solid fuel cells (IT-SOFCs).
Remark doi: 10.1115/1.4033526
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ID=351

Magnetron-Sputtered YSZ and CGO Electrolytes for SOFC

Authors A. A. Solovyev , A. V. Shipilova, I. V. Ionov, A. N. Kovalchuk, S. V. Rabotkin, V. O. Oskirko
Source
Journal of Electronic Materials
Time of Publication: 2016
Abstract Reactive magnetron sputtering has been used for deposition of yttria-stabilized ZrO2 (YSZ) and gadolinium-doped CeO2 (CGO) layers on NiO-YSZ commercial anodes for solid oxide fuel cells. To increase the deposition rate and improve the quality of the sputtered thin oxide films, asymmetric bipolar pulse magnetron sputtering was applied. Three types of anode-supported cells, with single-layer YSZ or CGO and YSZ/CGO bilayer electrolyte, were prepared and investigated. Optimal thickness of oxide layers was determined experimentally. Based on the electrochemical characteristics of the cells, it is shown that, at lower operating temperatures of 650C to 700C, the cells with single-layer CGO electrolyte are most effective. The power density of these fuel cells exceeds that of the cell based on YSZ single-layer electrolyte at the same temperature. Power densities of 650 mW cm−2 and 500 mW cm−2 at 700C were demonstrated by cells with single-layer YSZ and CGO electrolyte, respectively. Significantly enhanced maximum power density was achieved in a bilayer-electrolyte single cell, as compared with cells with a single electrolyte layer. Maximum power density of 1.25 W cm−2 at 800C and 1 W cm−2 at 750C under voltage of 0.7 V were achieved for the YSZ/CGO bilayer electrolyte cell with YSZ and CGO thickness of about 4 μm and 1.5 μm, respectively. This signifies that the YSZ thin film serves as a blocking layer to prevent electrical current leakage in the CGO layer, leading to the overall enhanced performance. This performance is comparable to the state of the art for cells based on YSZ/CGO bilayer electrolyte.
Keywords Solid oxide fuel cell CGO YSZ bilayer electrolyte magnetron sputtering pulse electron-beam treatment
Remark Link
ID=350

Characteristics of Cu and Mo-doped Ca3Co4O9−δ cathode materials for use in solid oxide fuel cells

Authors Sea-Fue Wang, Yung-Fu Hsu, Jing-Han Chang, Soofin Cheng, Hsi-Chuan Lu
Source
Ceramics International
Time of Publication: 2016
Abstract In this study, Cu and Mo ions were doped in Ca3Co4O9−δ to improve the electrical conductivity and electrochemical behavior of Ca3Co4O9−δ ceramic and the performance of a solid oxide fuel cell (SOFC) single cell based on NiO-SDC/SDC/doped Ca3Co4O9−δ-SDC were examined. Cu substitution in the monoclinic Ca3Co4O9−δ ceramic effectively enhanced the densification, slightly increased the grain size, and triggered the formation of some Ca3Co2O6; however, no second phase was found in porous Mo-doped Ca3Co4O9−δ ceramics even when the sintering temperature reached 1050 C. Substitution of Cu ions caused slight increase in the Co3+ and Co4+ contents and decrease in the Co2+ content; however, doping with Mo ions showed the opposite trend. Doping the Ca3Co4O9−δ ceramic with a small amount of Cu or Mo increased its electrical conductivity. The maximum electrical conductivity measured was 218.8 S cm−1 for the Ca3Co3.9Cu0.1O9−δ ceramic at 800 C. The Ca3Co3.9Cu0.1O9−δ ceramic with a coefficient of thermal expansion coefficient of 12.110−6 K−1 was chosen as the cathode to build SOFC single cells consisting of a 20 μm SDC electrolyte layer. Without optimizing the microstructure of the cathode or hermetically sealing the cell against the gas, a power density of 0.367 Wcm−2 at 750 C was achieved, demonstrating that Cu-doped Ca3Co4O9−δ can be used as a potential cathode material for IT-SOFCs.
Keywords Solid oxide fuel cell; Cathode; Impedance; Cell performance
Remark In Press, doi:10.1016/j.ceramint.2016.04.037
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ID=349

Synthesis and characterization of robust, mesoporous electrodes for solid oxide fuel cells

Authors Laura Almar, Alex Morata, Marc Torrell, Mingyang Gong, Meilin Liu, Teresa Andreu and Albert Tarancn
Source
Journal of Materials Chemistry A
Time of Publication: 2016
Abstract The use of mesoporous electrodes in solid oxide cells would lead to a significant enhancement of the performance due to their high surface area and large number of active sites for electrochemical reactions. However, their application in real devices is still hindered by the potential instability of the mesostructure and morphology at high temperatures required for device fabrication and under severe conditions for high-current, long-term operation. Here we report our findings on the preparation and characterization of mesoporous electrodes based on ceria infiltrated with catalysts: an anode consisting of a Ce0.8Sm0.2O1.9 (SDC) scaffold infiltrated with Ni and a cathode consisting of an SDC scaffold infiltrated with Sm0.5Sr0.5CoO3−δ (SSC). In particular, a doped-zirconia electrolyte supported cell with a mesoporous Ni–SDC anode and a mesoporous SSC–SDC cathode demonstrates an excellent peak power density of 565 mW cm−2 at 750 C (using humidified hydrogen as the fuel). More importantly, both mesoporous electrodes display remarkable stability, yielding a combined electrode virtual non-degradation for the last 500 hours of the test at a constant current density of 635 mA cm−2 at 750 C, demonstrating the potential of these mesoporous materials as robust electrodes for solid oxide fuel cells or other high-temperature electrochemical energy storage and conversion devices.
Remark DOI: 10.1039/C6TA00321D
Link
ID=347

Structural study and proton conductivity in BaCe0.7Zr0.25−xYxZn0.05O3 (x = 0.05, 0.1, 0.15, 0.2 & 0.25)

Authors Ahmed Afif, Nikdalila Radenahmad, Chee Ming Lim, Mohamad Iskandar Petra, Md. Aminul Islam, Seikh Mohammad Habibur Rahman, Sten Eriksson, Abul Kalam Azad
Source
International Journal of Hydrogen Energy
Time of Publication: 2016
Abstract Solid oxide fuel cell (SOFC) has been considered to generate power represented by conductivity. Zinc doped Barium Cerium Zirconium Yttrium oxide (BCZYZn) has been found to offer high protonic conductivity and high stability as being electrolyte for proton-conducting SOFCs. In this study, we report a new series of proton conducting materials, BaCe0.7Zr0.25−xYxZn0.05O3 (x = 0.05, 0.1, 0.15, 0.2 and 0.25). The materials were synthesized by solid state reaction route and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal expansion, particle size and impedance spectroscopy (IS). Rietveld analysis of the XRD data reveal a cubic perovskite structure with Pm-3m space group up to composition x = 0.15. For x = 0.15 and 0.20, the materials have structural phase change to orthorhombic in the Pbnm space group. Scanning electron microscopy images show high density materials. Thermal expansion measurements show that the thermal expansion coefficient is in the range 10.0–11.0 10−6/C. Impedance spectroscopy shows higher ionic conduction under wet condition compared to dry condition. Y content of 25% (BCZYZn25) exhibits highest conductivity of 1.84 10−2 S/cm in wet Argon. This study indicated that perovskite electrolyte BCZYZn is promising material for the next generation of intermediate temperature solid oxide fuel cells (IT-SOFCs).
Keywords Proton conductor; Sinterability; Rietveld refinement; Conductivity; SOFC electrolyte
Remark In Press, doi:10.1016/j.ijhydene.2016.02.135
Link
ID=318

EuBaCo2O5+δ-Ce0.9Gd0.1O2−δ composite cathodes for intermediate-temperature solid oxide fuel cells: high electrochemical performance and oxygen reduction kinetics

Authors Zhan Shi, Tian Xia, Fuchang Meng, Jingping Wang, Shengming Wu, Jie Lian, Hui Zhao, Chunbo Xu
Source
Electrochimica Acta
Volume: 174, Pages: 608–614
Time of Publication: 2015
Abstract The characteristics and electrochemical performance of double perovskite EuBaCo2O5+δ (EBCO) have been investigated as a composite cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The thermal expansion coefficients can be effectively reduced in the case of EBCO-Ce0.9Gd0.1O2−δ (CGO) composite cathodes. No chemical reactions between EBCO cathode and CGO electrolyte are observed after sintering at 1000 C for 24 h. The maximum electrical conductivities of EBCO-CGO materials reach 28-77 S cm−1 with the change of CGO weight ratio from 40 wt. % to 5 wt. %. Among all these components, the EBCO-10 wt. % CGO (EBCO-10CGO) composite cathode gives the lowest area-specific resistance of 0.055 and 0.26 Ω cm2 in air at 700 and 600 C, respectively. The maximum power density of Ni-CGO anode-supported single cell consisted of the EBCO-10CGO composite cathode and CGO electrolyte achieves 0.81 W cm−2 at 700 C. These results indicate that the EBCO-10CGO composite materials can be used as a promising cathode candidate for IT-SOFCs. Furthermore, the rate-limiting steps for the oxygen reduction reaction at the EBCO-10CGO composite cathode interface are determined to be the charge transfer and dissociation of adsorbed molecule oxygen processes.
Keywords Intermediate-temperature solid oxide fuel cells; cathode materials; electrochemical performance; oxygen reduction kinetics
Remark doi:10.1016/j.electacta.2015.06.059
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ID=315

Gd- and Pr-based double perovskite cobaltites as oxygen electrodes for proton ceramic fuel cells and electrolyser cells

Authors Ragnar Strandbakke, Vladimir A. Cherepanov, Andrey Yu. Zuev, Dmitry S. Tsvetkov, Christos Argirusis, Georgia Sourkouni, Stephan Prnte, Truls Norby
Source
Solid State Ionics
Volume: 278, Pages: 120–132
Time of Publication: 2015
Abstract Double perovskite oxides BaGd0.8La0.2Co2O6−δ (BGLC), BaGdCo1.8Fe0.2O6−δ (BGCF), BaPrCo2O6−δ (BPC) and BaPrCo1.4Fe0.6O6−δ (BPCF) were investigated as oxygen electrodes on mixed conducting BaZr0.7Ce0.2Y0.1O3 (BZCY72) electrolyte using impedance spectroscopy vs temperature, pO2, and pH2O. We propose and have applied a novel approach to extract and parameterise the charge transfer and diffusion impedances of the electrode reactions in a system comprising charge transport of protons, oxide ions, and electrons. Given by the properties of the BZCY72, transport of protons dominates at lower temperatures and high pH2O, oxide ions at higher temperatures, and electron holes increasingly at high temperatures and high pO2. The electrodes showed good performance, with the lowest total apparent polarisation resistance for BGLC/BZCY72 being 0.05 and 10 Ωcm2 at 650 and 350 C, respectively. The low temperature rate limiting reaction step is a surface related process, involving protonic species, with an activation energy of approximately 50 kJ mol−1 for BGLC/BZCY72. The oxide ion transport taking over at higher temperatures exhibits a higher activation energy typical of SOFC cathodes. Thermogravimetric studies revealed that BGLC exhibits considerable protonation at 300–400 C, which may be interpreted as hydration with an enthalpy of approximately –50 kJ mol−1. The resulting mixed proton electron conduction may explain its good performance as electrode on BZCY72.
Keywords PCFC; PCEC; P-MIEC; Proton conductor; Mixed conductivity; Double perovskite
Remark doi:10.1016/j.ssi.2015.05.014
Link
ID=313

Praseodymium-deficiency Pr0.94BaCo2O6-δ double perovskite: A promising high performance cathode material for intermediate-temperature solid oxide fuel cells

Authors Fuchang Meng, Tian Xia, Jingping Wang, Zhan Shi, Hui Zhao
Source
Journal of Power Sources
Volume: 239, Pages: 741–750
Time of Publication: 2015
Abstract Praseodymium-deficiency Pr0.94BaCo2O6-δ (P0.94BCO) double perovskite has been evaluated as a cathode material for intermediate-temperature solid oxide fuel cells. X-ray diffraction pattern shows the orthorhombic structure with double lattice parameters from the primitive perovskite cell in Pmmm space group. P0.94BCO has a good chemical compatibility with Ce0.9Gd0.1O1.95 (CGO) electrolyte even at 1000 C for 24 h. It is observed that the Pr-deficiency can introduce the extra oxygen vacancies in P0.94BCO, further enhancing its electrocatalytic activity for oxygen reduction reaction. P0.94BCO demonstrates the promising cathode performance as evidenced by low polarization are-specific resistance (ASR), e. g. 0.11 Ω cm2 and low cathodic overpotential e. g. −56 mV at a current density of −78 mA cm−2 at 600 C in air. These features are comparable to those of the benchmark cathode Ba0.5Sr0.5Co0.8Fe0.2O3-δ. The fuel cell CGO-Ni|CGO|P0.94BCO presents the attractive peak power density of 1.05 W cm−2 at 600 C. Furthermore, the oxygen reduction kinetics of P0.94BCO material is also investigated, and the rate-limiting steps for oxygen reduction reaction are determined.
Keywords Intermediate-temperature solid oxide fuel cell; Cathode material; Double perovskite; Electrochemical performance; Oxygen reduction reaction
Remark doi:10.1016/j.jpowsour.2015.06.007
Link
ID=302

Coated stainless steel 441 as interconnect material for solid oxide fuel cells: Evolution of electrical properties

Authors Jan Gustav Grolig , Jan Froitzheim, Jan-Erik Svensson
Source
Journal of Power Sources
Volume: 284, Pages: 321–327
Time of Publication: 2015
Abstract AISI 441 coated with a double layer coating of 10 nm cerium (inner layer) and 630 nm cobalt was investigated and in addition the uncoated material was exposed for comparison. The main purpose of this investigation was the development of a suitable ASR characterization method. The material was exposed to a simulated cathode atmosphere of air with 3% water at 850 C and the samples were exposed for up to 1500 h. We compared two methods of ASR measurements, an in-situ method where samples were measured with platinum electrodes for longer exposure times and an ex-situ method where pre-oxidized samples were measured for only very short measurement times. It was found that the ASR of ex-situ characterized samples could be linked to the mass gain and the electrical properties could be linked to the evolving microstructure during the different stages of exposure. Both the degradation of the electric performance and the oxygen uptake (mass gain) followed similar trends. After about 1500 h of exposure an ASR value of about 15 mΩcm2 was reached. The in-situ measured samples suffered from severe corrosion attack during measurement. After only 500 h of exposure already a value of 35 mΩcm2 was obtained.
Keywords ASR; Interconnect; AISI 441; SOFC; Corrosion; Platinum
Remark doi:10.1016/j.jpowsour.2015.03.029
Link
ID=297

Solid oxide fuel cells with (La,Sr)(Ga,Mg)O3-δ electrolyte film deposited by radio-frequency magnetron sputtering

Authors Sea-Fue Wang, His-Chuan Lu, Yung-Fu Hsu, Yi-Xuan Hu
Source
Journal of Power Sources
Volume: 281, Pages: 258–264
Time of Publication: 2015
Abstract In this study, solid oxide fuel cells (SOFCs) containing a high quality La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) film deposited on anode supported substrate using RF magnetron sputtering are successfully prepared. The anode substrate is composed of two functional NiO/Sm0.2Ce0.8O2-δ (SDC) composite layers with ratios of 60/40 wt% and 50/50 wt% and a current collector layer of pure NiO. The as-deposited LSGM film appears to be amorphous in nature. After post-annealing at 1000 C, a uniform and dense polycrystalline film with a composition of La0.87Sr0.13Ga0.85Mg0.15O3-δ and a thickness of 3.8 μm is obtained, which was well adhered to the anode substrate. A composite LSGM/La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) layer, with a ratio of 30/70 wt%, is used as the cathode. The SOFC prepared reveals a good mechanical integrity with no sign of cracking, delamination, or discontinuity among the interfaces. The total cell resistance of a single cell with LSGM electrolyte film declines from 0.60 to 0.10 Ω cm2 as the temperature escalates from 600 to 800 C and the open circuit voltage (OCV) ranges from 0.85 to 0.95 V. The maximum power density (MPD) of the single cell is reported as 0.65, 1.02, 1.30, 1.42, and 1.38 W cm−2 at 600, 650, 700, 750, and 800 C, respectively. The good cell performance leads to the conclusion that RF magnetron sputtering is a feasible deposition method for preparing good quality LSGM films in SOFCs.
Keywords Solid oxide fuel cell; Sputtering; Electrolyte; Doped lanthanum gallate
Remark doi:10.1016/j.jpowsour.2015.01.185
Link
ID=295

Binder Jetting: A Novel Solid Oxide Fuel-Cell Fabrication Process and Evaluation

Authors Guha Manogharan, Meshack Kioko, Clovis Linkous
Source
JOM
Volume: 67, Issue: 3, Pages: 660-667
Time of Publication: 2015
Abstract With an ever-growing concern to find a more efficient and less polluting means of producing electricity, fuel cells have constantly been of great interest. Fuel cells electrochemically convert chemical energy directly into electricity and heat without resorting to combustion/mechanical cycling. This article studies the solid oxide fuel cell (SOFC), which is a high-temperature (100C to 1000C) ceramic cell made from all solid-state components and can operate under a wide range of fuel sources such as hydrogen, methanol, gasoline, diesel, and gasified coal. Traditionally, SOFCs are fabricated using processes such as tape casting, calendaring, extrusion, and warm pressing for substrate support, followed by screen printing, slurry coating, spray techniques, vapor deposition, and sputter techniques, which have limited control in substrate microstructure. In this article, the feasibility of engineering the porosity and configuration of an SOFC via an additive manufacturing (AM) method known as binder jet printing was explored. The anode, cathode and oxygen ion-conducting electrolyte layers were fabricated through AM sequentially as a complete fuel cell unit. The cell performance was measured in two modes: (I) as an electrolytic oxygen pump and (II) as a galvanic electricity generator using hydrogen gas as the fuel. An analysis on influence of porosity was performed through SEM studies and permeability testing. An additional study on fuel cell material composition was conducted to verify the effects of binder jetting through SEM–EDS. Electrical discharge of the AM fabricated SOFC and nonlinearity of permeability tests show that, with additional work, the porosity of the cell can be modified for optimal performance at operating flow and temperature conditions.
Remark DOI 10.1007/s11837-015-1296-9
Link
ID=281

Structural and electrical study of samarium doped cerium oxide thin films prepared by e-beam evaporation

Authors Darius Virbukas, Mantas Sriubas, Giedrius Laukaitis
Source
Solid State Ionics
Time of Publication: 2014
Abstract Samarium doped cerium oxide (Sm0.15Ce0.85O1.925, SDC) thin films were grown on the Alloy 600 (Fe–Ni–Cr) and optical quartz (SiO2) substrates using e-beam deposition technique. Formed SDC thin films were characterized using different X-ray diffraction (XRD) techniques, scanning electron microscope (SEM), energy-dispersive spectrometry (EDS) and impedance spectroscopy. The deposition rate of formed SDC thin films was changed from 2 /s to 16 /s. XRD analysis shows that all thin films have a cubic (FCC) structure and repeat the crystallographic orientation of the initial powders evaporated with different deposition rate and on different substrates. The crystallite size increases from 7.7 nm to 10.3 nm and from 7.2 nm to 9.2 nm on Alloy 600 substrate and optical quartz (SiO2) substrate respectively as the thin film deposition rate increases. SEM images indicate a dense and homogeneous structure of all formed SDC thin films. The ionic conductivity depends on thin films density and blocking factor. The best ionic conductivity (σg = 1.34 Sm− 1 and σgb = 2.29 Sm −1 at 873 K temperature, activation energy ΔEg = 0.91 eV and ΔEgb = 0.99 eV) was achieved for SDC thin films formed at 4 /s deposition rate. It was found that the highest density (5.25 g/cm3) and the lowest relaxation time in grain (τg = 9.83 10− 7 s), and the lowest blocking factor (0.39) is in SDC thin films formed at 4 /s deposition rate. The deposition rate influences the stoichiometry of the formed SDC thin ceramic films.
Keywords Electron beam deposition; Samarium doped ceria oxide (SDC); Solid oxide fuel cells (SOFC); Ionic conductivity
Remark DOI: 10.1016/j.ssi.2014.09.036
Link
ID=277

Superior electrochemical performance and oxygen reduction kinetics of layered perovskite PrBaxCo2O5+δ (x = 0.90–1.0) oxides as cathode materials for intermediate-temperature solid oxide fuel cells

Authors Jingping Wang, Fuchang Meng, Tian Xia, Zhan Shi, Jie Lian, Chunbo Xu, Hui Zhao, Jean-Marc Bassat, Jean-Claude Grenier
Source
International Journal of Hydrogen Energy
Time of Publication: 2014
Abstract The layered perovskite PrBaxCo2O5+δ (PBxCO, x = 0.90–1.0) oxides have been synthesized by a solid-state reaction technique, and evaluated as the potential cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Room temperature X-ray diffraction patterns show the orthorhombic structures which double the lattice parameters from the perovskite cell parameter as a ≈ ap, b ≈ ap and c ≈ 2ap (ap is the cell parameter of the primitive perovskite) in the Pmmm space group. There is a good chemical compatibility between the PBxCO cathode and the Ce0.9Gd0.1O1.95 (CGO) electrolyte at 1000 C. The electrical conductivity and thermal expansion coefficient of PBxCO are improved due to the increased amount of electronic holes originated from the Ba-deficiency. The results demonstrate the high electrochemical performance of PBxCO cathodes, as evidenced by the super low polarization resistances (Rp) over the intermediate temperature range. The lowest Rp value, 0.042 Ω cm2, and the cathodic overpotential, −15 mV at a current density of −25 mA cm−2, are obtained in the PrBa0.94Co2O5+δ cathode at 600 C in air, which thus allow to be used as a highly promising cathode for IT-SOFCs. A CGO electrolyte fuel cell with the PrBa0.94Co2O5+δ cathode presents the attractive peak power density of ∼1.0 W cm−2 at 700 C. Furthermore, the oxygen reduction kinetics of the PrBa0.94Co2O5+δ cathode is also studied, and the rate-limiting steps for oxygen reduction reaction are determined at different temperatures.
Remark DOI: 10.1016/j.ijhydene.2014.09.041
Link
ID=276

Organic–Inorganic Hybrid Membranes Based on Sulfonated Poly(ether ether ketone) and Tetrabutylphosphonium Bromide Ionic Liquid for PEM Fuel Cell Applications

Authors Vijay Shankar Rangasamy, Savitha Thayumanasundaram, Niels de Greef, Jin Won Seo and Jean-Pierre Locquet
Source
European Journal of Inorganic Chemistry
Time of Publication: 2014
Abstract Ionic liquids (ILs), with their inherent ionic conductivity and negligible vapor pressure, can be exploited in proton exchange membrane (PEM) fuel cells for which thermal management is a major problem and the cell operation temperature is limited by the boiling point of water. In this work, sulfonated poly(ether ether ketone) (SPEEK) membranes were modified by the incorporation of tetrabutylphosphonium bromide ([P4 4 4 4]Br) by solvent-casting. Electrochemical impedance spectroscopy (EIS) was used to study the electrical properties of the modified membranes. Simultaneous TGA and FTIR studies were used to evaluate the thermal stability and chemical structure of the modified membranes, respectively. 1H NMR spectroscopy was applied to probe the changes in the chemical environment due to the interaction between the ionic liquid and the polymer. Mechanical properties were studied by dynamic mechanical analysis. The temperature-dependent behavior of the viscosity of the [P4 4 4 4]Br ionic liquid was observed to obey the Vogel–Fulcher–Tammann (VFT) equation, and was correlated to the ion-conducting properties of the IL-doped SPEEK membranes.
Remark DOI: 10.1002/ejic.201402558
Link
ID=270

Conductivity and oxygen reduction activity changes in lanthanum strontium manganite upon low-level chromium substitution

Authors George Tsekouras, Artur Braun
Source
Solid State Ionics
Volume: 266, Pages: 19-24
Time of Publication: 2014
Abstract On the timescale of solid oxide fuel cell (SOFC) system lifetime requirements, the thermodynamically predicted low-level substitution of chromium on the B-site of (La,Sr)MnO3 could be a source of cathode degradation underlying more overt and well-known chromium poisoning mechanisms. To study this phenomenon in isolation, electronic conductivity (σ) and electrochemical oxygen reduction activity of the (La0.8Sr0.2)0.98CrxMn1−xO3 model series (x = 0, 0.02, 0.05 or 0.1) were measured in air between 850 and 650 C. Depending on the extent of chromium substitution and the measurement temperature, electrochemical impedance spectroscopy (EIS) results could be deconvoluted into a maximum of three contributions reflecting possible limiting processes such as oxide ion transport and dissociative adsorption. Chromium substitution resulted in lowered σ (from 174 S cm− 1 (x = 0) to 89 S cm− 1 (x = 0.1) at 850 C) and a steady rise in associated activation energy (Ea) (from 0.105 0.001 eV (x = 0) to 0.139 0.001 eV (x = 0.1)). From EIS analyses, ohmic and polarisation resistances increased, whilst Ea for the overall oxygen reduction reaction also increased from 1.39 0.04 eV (x = 0) to 1.48–1.54 0.04 eV upon chromium substitution.
Keywords Solid oxide fuel cell; Lanthanum strontium manganite; Chromium poisoning; Electronic conductivity; Electrochemical impedance spectroscopy
Remark Link
ID=269

The effect of calcination temperature on the electrochemical properties of La0.3Sr0.7Fe0.7Cr0.3O3−x (LSFC) perovskite oxide anode of solid oxide fuel cells (SOFCs)

Authors Yifei Sun, Ning Yan, Jianhui Li, Huayi Wu, Jing-Li Luo, Karl T. Chuang
Source
Sustainable Energy Technologies and Assessments
Volume: 8, Pages: 92-98
Time of Publication: 2014
Abstract A series of perovskite structure anode materials, LSFC, was successfully prepared by a glycine combustion process and further calcined at different temperatures. The electrochemical properties of anodes prepared at various calcination temperatures (1100 C, 1200 C and 1300 C) were investigated. The calcination temperature had no significant influence on the morphology of the material but showed obvious influences on the particle sizes and electrochemical properties of the materials. Higher calcination temperature results in sharper X-ray diffractometer (XRD) diffraction peaks of the materials with larger particle sizes and higher electrical conductivity. However materials calcined at higher temperature had much smaller BET surface area resulting in lower triple phase boundary (TPB). The electrochemical performance test exhibited that LSFC anode material sintered at 1100 C exhibited the smallest area specific resistance (ASR) value in H2 at operating temperatures from 700 to 900 C. For proton conducting SOFCs (PC-SOFCs) fed by syngas, the cell with anode calcined at 1100 C also showed highest power density output of 120 mW/cm2 at 750 C, which was almost three times higher than that of the cell with anode calcined at 1300 C.
Keywords Solid oxide fuel cell; Calcination temperature; Electrochemical properties; Perovskite
Remark Link
ID=267

MICROWAVE SINTERING OF Sr AND Mg-DOPED LANTHANUM GALLATE (LSGM) SOLID ELECTROLYTES

Authors Cristian Andronescu, Victor Fruth, Enikoe Volceanov, Rares Scurtu, Cornel Munteanu, Maria Zaharescu
Source
Romanian journal of materials
Time of Publication: 2014-01
Abstract Sr2+ and Mg2+ simultaneously doped lanthanum gallate (LSGM) powders, prepared by a modified Pechini route using polyvinyl alcohol (PVA) as polymeric alcohol, were densified using an activated microwave technique at 2.45 GHz, to develop a dense stable electrolyte for application in intermediate temperatures solid oxide fuel cells (IT-SOFC). Thermal behaviour of precursors was investigated by means of differential thermal analysis combined with thermogravimetric analysis (DTA/TGA). The powders and sintered samples were characterized using scanning electron microscopy and energy dispersive analysis (SEM-EDAX), X-ray diffraction (XRD) and infrared spectroscopy (FT-IR). The thermal expansion coefficient (TEC) and ionic conductivity of the sintered samples were also evaluated. Fine, homogeneous and high density pellets of almost pure LSGM phase were obtained after sintering at 14000C for a short period time in an activated microwave field. Using activated microwave field, due to the volumetric in situ heating, the sintering process is highly specific and instantaneous, leading to a faster kinetics compared to the conventional process (electric oven). With an optimized sintering schedule, a fine grained and dense microstructure of the samples were obtained.
Remark Link
ID=266

Magnetron formation of Ni/YSZ anodes of solid oxide fuel cells

Authors A. A. Solov’ev, N. S. Sochugov, I. V. Ionov, A. V. Shipilova, A. N. Koval’chuk
Source
Russian Journal of Electrochemistry
Volume: 50, Issue: 7, Pages: 647-655
Time of Publication: 2014
Abstract Physico-chemical and structural properties of nanocomposite NiO/ZrO2:Y2O3 (NiO/YSZ) films applied using the reactive magnetron deposition technique are studied for application as anodes of solid oxide fuel cells. The effect of oxygen consumption and magnetron power on the discharge parameters is determined to find the optimum conditions of reactive deposition. The conditions for deposition of NiO/YSZ films, under which the deposition rate is maximum (12 μm/h), are found and the volume content of Ni is within the range of 40–50%. Ni-YSZ films reduced in a hydrogen atmosphere at the temperature of 800C have a nanoporous structure. However, massive nickel agglomerates are formed in the course of reduction on the film surface; their amount grows at an increase in Ni content in the film. Solid oxide fuel cells with YSZ supporting electrolyte and a LaSrMnO3 cathode are manufactured to study electrochemical properties of NiO/YSZ films. It is shown that fuel cells with a nanocomposite NiO/YSZ anode applied using a magnetron sputtering technique have the maximum power density twice higher than in the case of fuel cells with an anode formed using the high-temperature sintering technique owing to a more developed gas-anode-electrolyte three-phase boundary.
Remark Link
ID=265

Full ceramic micro solid oxide fuel cells: towards more reliable MEMS power generators operating at high temperatures

Authors I. Garbayo, D. Pla, A. Morata, L. Fonseca, N. Sabat and A. Tarancn
Source
Energy Environ. Sci.
Time of Publication: 2014
Abstract Batteries, with a limited capacity, have dominated the power supply of portable devices for decades. Recently, the emergence of new types of highly efficient miniaturized power generators like micro fuel cells has opened up alternatives for continuous operation on the basis of unlimited fuel feeding. This work addresses for the first time the development of a full ceramic micro solid oxide fuel cell fabricated in silicon technology. This full-ceramic device represents a new generation of miniaturized power generators able to operate at high temperatures, and therefore able to work with a hydrocarbon fuel supply. Dense yttria-stabilized zirconia free-standing large-area membranes on micromachined silicon were used as the electrolyte. Thin-film porous electrodes of La0.6Sr0.4CoO3−δ and gadolinia-doped ceria were employed as cathode and anode materials, respectively. The electrochemical performance of all the components was evaluated by partial characterization using symmetrical cells, yielding excellent performance for the electrolyte (area specific resistance of 0.15 Ω cm2 at temperatures as low as 450 C) and the electrodes (area specific resistance of the cathode and anode below 0.3 Ω cm2 at 700 C). A micro solid oxide fuel cell with an active area of 2 mm2 and less than 1 micrometer in thickness was characterized under fuel cell conditions, using hydrogen as a fuel and air as an oxidant. A maximum power density of 100 mW cm−2 and 2 mW per single membrane was generated at 750 C, having an open circuit voltage of 1.05 V. Impedance spectroscopy of the all-ceramic membrane showed a total area-specific resistance of [similar]3.5 Ω cm2.
Remark DOI: 10.1039/C4EE00748D
Link
ID=255

Oxide ion transport in (Nd2−xZrx)Zr2O7+δ electrolytes by an interstitial mechanism

Authors A.V. Shlyakhtina, D.A. Belov, A.V. Knotko, M. Avdeev, I.V. Kolbanev, G.A. Vorobieva, O.K. Karyagina, L.G. Shcherbakova
Source
Journal of Alloys and Compounds
Volume: 603, Issue: 5, Pages: 274–281
Time of Publication: 2014
Abstract We have studied the structure and transport properties of ten (Nd2−xZrx)Zr2O7+x/2 (x = 0–1.27) solid solutions, which lie in the ZrO2–Nd2Zr2O7 isomorphous miscibility range. Major attention has been focused on the pyrochlore-like (Nd2−xZrx)Zr2O7+x/2 solid solutions with x = 0–0.78, which are thought to be potential interstitial oxide ion conductors. The X-ray and neutron diffraction results demonstrate that the (Nd2−xZrx)Zr2O7+x/2 (x = 0–1.27) solid solutions undergo an order–disorder (pyrochlore–defect fluorite) structural phase transition. The (Nd2−xZrx)Zr2O7+x/2 (x = 0.2–0.78) have the bulk conductivity, ∼(1.2–4) 10–3 S/cm at 750 C, which is two orders of magnitude higher than that of the ordered pyrochlore Nd2Zr2O7. An attempt has been made to determine the interstitial oxygen content of (Nd2−xZrx)Zr2O7+x/2 (x = 0.2; 0.67) in a reducing atmosphere using thermogravimetry and mass spectrometry. It has been shown that no reduction occurs in the NdZrO system, where neodymium has only one oxidation state, 3+.
Keywords Fuel cells; Ionic conduction; Electrochemical impedance spectroscopy; Neutron diffraction; X-ray diffraction; SEM
Remark http://dx.doi.org/10.1016/j.jallcom.2014.03.068
Link
ID=250

Solid Oxide-Molten Carbonate Nano-composite Fuel Cells: Particle Size Effect

Authors Shalima Shawuti, Mehmet A. Gulgun
Source
Journal of Power Sources
Time of Publication: 2014
Abstract Varying the amount of specific interface area in the CeO2-Na2CO3 nano-composite fuel cell electrolyte helped reveal the role of interfaces in ionic conductivity. We mixed ceria particles with micrometer or nanometer size distributions to obtain a specific surface area (SSA) in the composite from 47 m2/g to 203 m2/g. Micro-structural investigations of the nano-composite showed that the Na2CO3 phase serves as the glue in the microstructure, while thermal analysis revealed a glass transition-like behavior at 350 C. High SSA enhanced the ionic conductivity significantly at temperatures below 400 C. Moreover, the activation energy for the Arrhenius conductivity (σT) of the composites was lower than that of the Na2CO3 phase. This difference in the activation energies is consistent with the calculated dissociation energy of the carbonate phase. The strong dependence of conductivity on the SSA, along with differences in the activation energies, suggests that the oxide surface acted as a dissociation agent for the carbonate phase. A model for the solid composite electrolyte is proposed: in the nano-composite electrolyte, the oxide surface helps Na2CO3 dissociate, so that the "liberated" ions can move more easily in the interaction region around the oxide particles, thus giving rise to high ionic conductivities.
Keywords composite electrolyte; ionic conductivity; impedance spectroscopy; SOFC; interphase; activation energy
Remark in press, http://dx.doi.org/10.1016/j.jpowsour.2014.05.010
Link
ID=247

Doped Germanate-Based Apatites as Electrolyte for Use in Solid Oxide Fuel Cells

Authors S.-F. Wang, Y.-F. Hsu, W.-J. Lin and K. Kobayashi
Source
Fuel Cells
Time of Publication: 2014
Abstract Apatite ceramics, known for their good electrical conductivities, have garnered substantial attention as an alternative electrolyte for solid oxide fuel cells (SOFCs). However, studies focusing on the electrochemical performances of SOFCs with apatities as electrolytes remain rare, partly due to their high sintering temperature. In this study, the effects of Mg2+, Al3+, Ga3+, and Sn4+ dopants on the characteristics of La9.5Ge6O26  δ are examined and their potential for use as SOFC electrolytes evaluated. The results indicate that La9.5Ge5.5Al0.5O26 is stabilized into a hexagonal structure, while the La9.5Ge5.5Sn0.5O26.25, La9.5Ge5.5Ga0.5O26, and La9.5Ge5.5Mg0.5O25.75 ceramics reveal triclinic cells accompanied with the second phase La2Sn2O7 or La2GeO5. The study further demonstrates that a high sintering temperature is needed for both the La9.5Ge5.5Mg0.5O25.75 and the La9.5Ge5.5Sn0.5O26.25 ceramics, and the worst electrical conductivity among the examined systems appears in the La9.5Ge5.5Ga0.5O26 ceramic. The La9.5Ge5.5Al0.5O26 ceramic is accordingly selected for cell evaluation due to its ability to reach densification at 1,350 C, its good electrical conductivity of 0.026 S cm–1 at 800 C, and its acceptable thermal expansion coefficient of 10.1  10–6 K–1. The maximum power densities of the NiO-SDC/La9.5Ge5.5Al0.5O26/LSCF-SDC single cell are found to be respectively 0.22, 0.16, 0.11, and 0.07 W cm–2 at 950, 900, 850, and 800 C.
Keywords Apatites; Cell Performance; Electrolyte; Impedance; Solid Oxide Fuel Cell
Remark Article first published online: 19 FEB 2014 DOI: 10.1002/fuce.201300093
Link
ID=237

Effect of Ni Concentration on Phase Stability, Microstructure and Electrical Properties of BaCe0.8Y0.2O3-δ - Ni Cermet SOFC Anode and its application in proton conducting ITSOFC

Authors Pooja Sawant, S. Varma, M.R. Gonal, B.N. Wani, Deep Prakash, S.R. Bharadwaj
Source
Electrochimica Acta
Time of Publication: 2013
Abstract In this work we have studied the effect of Ni concentration on phase stability, microstructure and electrical properties of BaCe0.8Y0.2O3-δ (BCY)-Ni cermet SOFC anode. It has been seen that Ni forms composite with BCY without forming any solid solution in both oxidized and reduced state. Also, microstructural analysis reveals the effect of Ni on porosity and triple phase boundaries necessary for electrochemical reactions during cell operation. Electrical conductivity values obtained from dc four probe technique in H2 atmosphere increase with an increase in Ni content. Composites with low vol% of Ni contents i.e. 19% (Ni19) and 26% (Ni26) show predominantly semiconductor-like behaviour whereas higher vol% viz. 35% (Ni35), 45% (Ni45) and 56% (Ni56) composites show electronic conductivity behaviour. This confirms that electronic conduction occurs through metallic Ni phase. Also, anode supported single cell for proton conducting SOFC has been fabricated using Ni35 composition and its current-potential characteristics measured at different temperatures.
Keywords Cermet; X-ray diffraction; Electrical conductivity; Four probe; Single Cell
Remark Available online 25 December 2013
Link
ID=228

Nanocrystalline Sm0.5Sr0.5CoO3−δ synthesized using a chelating route for use in IT-SOFC cathodes: microstructure, surface chemistry and electrical conductivity

Authors Rares Scurtu, Simona Somacescu, Jose Maria Calderon-Moreno, Daniela Culita, Ion Bulimestru, Nelea Popa, Aurelian Gulea, Petre Osiceanu
Source
Journal of Solid State Chemistry
Time of Publication: 2013
Abstract Nanocrystalline Sm0.5Sr0.5CoO3−δ powders were synthesized by a chelating route using different polyfunctional HxAPC acids (APC=aminopolycarboxylate; x= 3, 4, 5). Different homologous aminopolycarboxylic acids, namely nitrilotriacetic (H3nta), ethylenediaminetetraacetic (H4edta), 1,2-cyclohexanediaminetetracetic (H4cdta) and diethylenetriaminepentaacetic (H5dtpa) acid, were used as chelating agents to combine Sm, Sr, Co elements into a perovskite structure. The effects of the chelating agents on the crystalline structure, porosity, surface chemistry and electrical properties were investigated. The electrical properties of the perovskite-type materials emphasized that their conductivities in the temperature range of interest (600–800 C) depend on the nature of the precursors as well as on the presence of a residual Co oxide phase as shown by XRD and XPS analysis. The surface chemistry and the surface stoichiometries were determined by XPS revealing a complex chemical behavior of Sr that exhibits a peculiar „surface phase” and „bulk phase” chemistry within the detected volume (<10 nm).
Keywords Cathode; Perovkites; Electrical Conductivity; XPS; IT-SOFC
Remark Available online 5 November 2013
Link
ID=224

Galliosilicate glasses for viscous sealants in solid oxide fuel cell stacks: Part III: Behavior in air and humidified hydrogen

Authors T. Jin, M.O. Naylor, J.E. Shelby, S.T. Misture
Source
International Journal of Hydrogen Energy
Time of Publication: 2013
Abstract Optimized boro-galliosilicate glasses were selected to evaluate their viscous sealing performance in both air and humidified hydrogen atmospheres. Selected low-alkali and alkali-free glasses show excellent performance, with viscous behavior maintained for more than 1000 h in wet hydrogen. Candidate sealants were thermally treated at 850 and 750 C for up to 1000 h in contact with alumina coated 441 stainless steel (Al-SS) and 8 mol% yttria-stabilized zirconia (8YSZ). Each sealant crystallizes appreciably by 1000 h, and their coefficients of thermal expansion range from 10.2 to 11.7 10−6 K−1, 100–400 C. The remnant amorphous phases in most of the partially crystallized sealants show softening points near or below the target operating temperatures, thus enabling viscous sealing. Humidified hydrogen in general increases the rate of crystallization but does not change the crystalline phases formed or interactions with 8YSZ. For the low-alkali GaBA series, wet H2 enhances the interfacial interaction between potassium in the glass phase and the protective alumina coating on the stainless steel.
Keywords Solid oxide fuel cell; Sealing glass; Galliosilicate; Thermal expansion; Hydrogen
Remark Available online 25 October 2013
Link
ID=208

Effects of Nb5+, Mo6+, and W6+ dopants on the germanate-based apatites as electrolyte for use in solid oxide fuel cells

Authors Sea-Fue Wang, Yung-Fu Hsu, Wan-Ju Lin
Source
International Journal of Hydrogen Energy
Volume: 38, Issue: 27, Pages: 12015–12023
Time of Publication: 2013-09
Abstract Rare information is available in the literature on the cell performance of the solid oxide fuel cells (SOFCs) using apatites known for their good electrical conductivity as electrolyte materials. In this study, La9.5Ge5.5Nb0.5O26.5, La9.5Ge5.5Mo0.5O26.75, and La9.5Ge5.5W0.5O26.75 ceramics were prepared and characterized. The results indicated that the La9.5Ge5.5Nb0.5O26.5 and La9.5Ge5.5W0.5O26.75 ceramics reported hexagonal phase, while the La9.5Ge5.5Mo0.5O26.75 ceramic demonstrated triclinic symmetry. Among the apatities evaluated, La9.5Ge5.5Nb0.5O26.5 sintered at 1450 C showed the best conduction with an electrical conductivity value of 0.045 S/cm at 800 C. Button cells of NiO–SDC/La9.5Ge5.5Nb0.5O26.5/LSCF–SDC were built and revealed good structural integrity. The total ohmic resistance (R0) and interfacial polarization resistance (RP) of the cell read 0.428 and 0.174 Ω cm2 and 0.871 and 1.164 Ω cm2, respectively at 950 and 800 C. The maximum power densities (MPD) of the single cell at 950 and 800 C were respectively 0.363 and 0.095 W cm−2. Without optimizing the anode and cathode as well as hermetic sealing of the cell against the gas, the study found the performance of the single cell with the pure La9.5Ge5.5Nb0.5O26.5 as its electrolyte material superior to those of the SOFC cells with a YSZ electrolyte of comparable thickness shown in the literature.
Keywords Solid oxide fuel cell; Apatite; Impedance; Cell performance
Remark Link
ID=191

Characteristics of SrCo1 − xSnxO3 − δ cathode materials for use in solid oxide fuel cells

Authors Sea-Fue Wang, Yung-Fu Hsu, Chun-Ting Yeh, Chien-Chung Huang, Hsi-Chuan Lu
Source
Solid State Ionics
Volume: 227, Pages: 10–16
Time of Publication: 2012-10
Abstract In this study, introduction of tin ions in the SrCoO3 − δ oxide is attempted to modify its electrochemical behavior for serving as a cathode of intermediate-temperature solid oxide fuel cells (IT-SOFCs). Doping of tin ions appears to stabilize the cubic Pm-3m phase of the SrCo1 − ySnyO3 − δ ceramics but generates SrSnO3 precipitates and inhibits the grain growth as y value rises to a level greater than 10%. Obtained at 550 C, the maximum electrical conductivity of SrCo0.95Sn0.05O3 − δ reads 545 S cm− 1. Single cells with a structure of NiO–Sm0.2Ce0.8O2 − δ (SDC)/SDC/SrCo0.95Sn0.05O3 − δ–SDC are built and characterized. Though SrCo0.95Sn0.05O3 − δ is regarded as an MIEC (mixed ionic/electronic conductivity material), adding SDC to SrCo0.95Sn0.05O3 − δ guarantees good adhesion to and fine electrical contact with the electrolyte layer, thereby contributing to the reduction in R0 and RP values. The single cell with the SrCo0.95Sn0.05O3 − δ–SDC composite cathode at 700 C registers respectively an R0 value of 0.044 Ω cm2 and an RP value of 0.109 Ω cm2. In the absence of microstructure optimization and hermetic sealing of cells, a high power density of 0.847 W cm− 2 is reached. SrCo1 − ySnyO3 − δ thus emerges to be a promising cathode material for IT-SOFCs applications.
Keywords Solid oxide fuel cell; Cathode; Impedance; Cell performance
Remark Link
ID=185

Investigating Reliability on Fuel Cell Model Identification. Part II: An Estimation Method for Stochastic Parameters

Authors L. Tsikonis, S. Diethelm, H. Seiler, A. Nakajo, J. Van herle, D. Favrat
Source
Fuel Cells
Time of Publication: 2012-08
Abstract An alternative way to process data from polarization measurements for fuel cell model validation is proposed. The method is based on re- and subsampling of I–V data, with which repetitive estimations are obtained for the model parameters. This way statistics such as standard deviations and correlations between the parameters may be experimentally derived. Histograms may also be produced, approximating the probability distributions that they follow. Two experimental case studies are discussed. In the first case, observations are made on the behavior of the parameter values for two mathematical models. As the number of data points (measurement points) employed in the estimation of the parameters increases, parameters with high variances converge to specific values. On the contrary, parameters with small variances diverge linearly. The parameters' histograms do not usually follow normal distributions rather they show a connection between the number of peaks in the graphs and correlations of the parameters. The second case study is an application on a fast degraded SOFC button cell, where the values and the histograms of the parameters are compared before and after degradation.
Keywords Data Fitting; Design of Experiments; Diagnostics; Fast Degradation; Identification; Parameter Estimation; Polarization Curves; Robust Regression; Solid Oxide Fuel cells; Stein's Paradox
Remark DOI: 10.1002/fuce.201200031
Link
ID=182

Sr1−xPrxCo0.95Sn0.05O3−δ ceramic as a cathode material for intermediate-temperature solid oxide fuel cells

Authors Sea-Fue Wang, Yung-Fu Hsu, Hsi-Chuan Lu, Chien-Chung Huang, Chun-Ting Yeh
Source
International Journal of Hydrogen Energy
Volume: 37, Issue: 17, Pages: 12548–12556
Time of Publication: 2012-10
Abstract In this study, the physical properties of the Sr1−xPrxCo0.95Sn0.05O3−δ ceramics were measured and their potential for use as a cathode material of intermediate-temperature solid oxide fuel cells (IT-SOFCs) was evaluated. A cubic phase was retained in all of the Sr1−xPrxCo0.95Sn0.05O3−δ ceramics. Analysis of the temperature-dependent conductivity found the SrCo0.95Sn0.05O3−δ and Sr0.9Pr0.1Co0.95Sn0.05O3−δ ceramics exhibiting semiconductor-like behavior below 550 C and metal-like behavior above the same temperature. The Sr0.8Pr0.2Co0.95Sn0.05O3−δ and Sr0.7Pr0.3Co0.95Sn0.05O3−δ ceramics, however, reported a metal-like conductivity in the whole temperature range. The electrical conductivities of the Sr0.8Pr0.2Co0.95Sn0.05O3−δ ceramic at 500 C and 700 C read respectively 1250 S/cm and 680 S/cm, both of which were superior than those in most of the common perovskites. Single cells with a structure of NiO–Sm0.2Ce0.8O2−δ (SDC)/SDC/Sr0.8Pr0.2Co0.95Sn0.05O3−δ-SDC were built and characterized. Addition of SDC in Sr0.8Pr0.2Co0.95Sn0.05O3−δ emerged to be a crucial factor reducing the ohmic resistance (R0) and polarization resistance (RP) of the cell by facilitating a better adhesion to and electrical contact with the electrolyte layer. The R0 and RP of the cell read respectively 0.068 Ω cm2 and 0.0571 Ω cm2 at 700 C and 0.298 Ω cm2 and 1.310 Ω cm2 at 550 C. With no microstructure optimization and hermetic sealing of the cells, maximum power density (MPD) and open circuit voltage (OCV) reached respectively 0.872 W/cm2 and 0.77 V at 700 C and 0.482 W/cm2 and 0.86 V at 550 C. It is evident that Sr1−xPrxCo0.95Sn0.05O3−δ is a promising cathode material for IT-SOFCs.
Keywords Solid oxide fuel cell; Cathode; Impedance; Cell performance
Remark Link
ID=174

High Power Plasma Sprayed Intermediate Temperature Solid Oxide Fuel Cells with Sm0.5Sr0.5CoO3-δ Cathode

Authors Chang-sing Hwang , Chun-Huang Tsai, Chun-Liang Chang, Jen-Feng Yu, Sheng-Hui Nien
Source
Procedia Engineering
Volume: 36, Pages: 81–87
Time of Publication: 2012-05
Abstract The cells with porous Ni/Fe(∼10 wt%) metal plate as a supporting substrate, double layers of La0.75Sr0.25Cr0.5Mn0.5 O3-δ (LSCM) and nanostructured Ce0.55La0.45O2-δ/Ni (LDC/Ni) as an anode, LDC as an anode interlayer, La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) as an electrolyte, LSGM/Sm0.5Sr0.5CoO3-δ (SSC) as a cathode interlayer and SSC as a cathode current collector, were prepared by atmospheric plasma spraying (APS) coating processes followed by a heating treatment. The current-voltage-power and AC impedance measurement results show that the prepared cell heat-treated at 850 C for 3 hours in air with a dead load of 1000 g cm-2 has an attracting performance. The measured maximum output power densities of this cell have reached 0.777, 0.742, 0.659, 0.542, 0.393, and 0.250 W cm-2 at 800, 750, 700, 650, 600, and 550 C respectively. The measured ohmic and polarization resistances are 0.241, 0.254, 0.282, 0.328, 0.42, 0.62 and 0.055, 0.064, 0.083, 0.128, 0.23, 0.471 Ω cm2 at 800, 750, 700, 650, 600, and 550 C respectively. After correction of the resistance inside the ProboStat system, the predicted actual maximum power densities that a cell can deliver are 1.95, 1.613, 1.186, 0.823, 0.512, and 0.293 W cm-2 at 800, 750, 700, 650, 600, and 550 C respectively.
Keywords Atmospheric plasma spray; solid oxide fuel cells; metal-supported; nanostructured; Sm0.5Sr0.5CoO3-δ
Remark Link
ID=169

SrCo1−xSbxO3−δ cathode materials prepared by Pechini method for solid oxide fuel cell applications

Authors Sea-Fue Wang, Hsi-Chuan Lu, Yung-Fu Hsu, Chien-Chung Huang, Chun-Ting Yeh
Source
Ceramics International
Volume: 38, Issue: 7, Pages: 5941–5947
Time of Publication: 2012-09
Abstract In this study, SrCo1−ySbyO3−δ powders were prepared by a modified Pechini method. According to the study results, the cubic Pm3m phase of the SrCo1−ySbyO3−δ ceramics was obtained as 10% of cobalt ions were substituted by antimony ions. Doping of Sb3+ ions appeared both to stabilize the Pm3m phase of the SrCo1−ySbyO3−δ ceramics and to enhance densification and retard grain growth. The coefficient of thermal expansion of the SrCo1−xSbxO3−δ ceramics increased with the content of the antimony ions, ranging from 10.17 to 15.37 ppm/C at temperatures lower than the inflection point (ranging from 450 C to 550 C) and from 22.16 to 29.29 ppm/C at higher temperatures. For the SrCo0.98Sb0.02O3−δ ceramic, electrical conductivity reached a maximum of 507 S/cm at 450 C. The ohmic and polarization resistances of the single cell with the pure SrCo0.98Sb0.02O3−δ cathode at 700 C read respectively 0.298 Ω cm2 and 0.560 Ω cm2. The single cell with the SrCo0.98Sb0.02O3−δ-SDC composite cathode appeared to reduce the impedances with the R0 and RP at 700 C reading respectively 0.109 Ω cm2 and 0.127 Ω cm2. Without microstructure optimization and measured at 700 C, the single cells with the pure SrCo0.98Sb0.02O3−δ cathode and the SrCo0.98Sb0.02O3−δ-SDC composite cathode, demonstrated maximum power densities of 0.100 W/cm2 and 0.487 W/cm2. Apparently, SrCo1−ySbyO3−δ is a potential cathode for use in IT-SOFCs.
Keywords Solid oxide fuel cell; Cathode; Impedance; Cell performance
Remark Available online 19 April 2012
Link
ID=166

Preparation and characterization of composite membranes based on sulfonated PEEK and AlPO4 for PEMFCs

Authors Vijay Shankar Rangasamy, Savitha Thayumanasundaram, Niels De Greef, Jin Won Seo, Jean-Pierre Locquet
Source
Solid State Ionics
Volume: 219, Pages: 83–89
Time of Publication: 2012-05
Abstract Sulfonated poly(ether ether ketone) (PEEK) and their composites are considered one of the most promising alternatives for Nafion, the industry benchmark for electrolytic membranes in proton exchange membrane (PEM) fuel cells. In the present study, PEEK was non-homogeneously sulfonated using concentrated H2SO4 at different temperatures (room temperature, 60 C, and 80 C) and time durations (5, 7, 48, and 72 h). Composite membranes of SPEEK with different weight ratios of AlPO4 synthesized by sol–gel were also prepared. Depending on the degree of sulfonation (DS), the Ion Exchange Capacity (IEC) of the membranes varied from 1.06 to 2.9 meq g− 1. XRD results show the increasing amorphous nature of the membranes with increase in IEC and DS value. The water uptake of the membranes also increased with DS. Simultaneous TGA–FTIR measurement of the composite membranes showed better thermal stability compared to pure SPEEK membranes. The water uptake and proton conductivity of the composite SPEEK membranes were found to be lower than that of pure SPEEK membranes, while the composite membranes exhibited a better swelling behavior and mechanical stability than the pure SPEEK samples.
Keywords Proton exchange membrane (PEM); Composite membranes; Sulfonated poly(etheretherketone) (SPEEK); Proton conductivity; Ion exchange capacity (IEC); Sol–gel
Remark Link
ID=154

Influence of Microwave-Assisted Pechini Method on La0.80Sr0.20Ga0.83Mg0.17O3–δ Ionic Conductivity

Authors S. Boldrini, C. Mortal, S. Fasolin, F. Agresti, L. Doubova, M. Fabrizio, and S. Barison
Source
Fuel Cells
Volume: 12, Issue: 1, Pages: 54–60
Time of Publication: 2012-02
Abstract With the aim of investigating the microwave influence on the electrolyte material properties, La0.80Sr0.20Ga0.83Mg0.17O2.815 was prepared by both a conventional and a microwave-assisted sol–gel Pechini method. With respect to the conventional Pechini method (hereafter SGP), the microwave assisted process (hereafter MWA-SGP) guaranteed a faster procedure, reducing the time needed to remove the excess solvents to complete the polyesterification reaction from some days to a few hours. In fact, when a MWA-SGP method was used, powders having higher phase purity were obtained. The sintering process at 1,450 C of the powders prepared by both methods yielded pellets with similar density values (≥92% of theoretical). Nevertheless, only by microwave-assisted process single-phase products were obtained and no secondary phases such as tetragonal LaSrGaO4 and LaSrGa3O7 were detected. These by-products have been demonstrated to be detrimental for conductivity. Indeed, pellets obtained by MWA-SGP method showed oxygen ionic conductivity values higher (about 30–40%) than those checked for SGP samples, thus demonstrating the important role of the microwave process on reducing time and costs and on improving the electrolyte properties.
Keywords Ionic Conductivity;IT-SOFC;Microwave Processing;(Sr, Mg)-Doped LaGaO3;Sol–Gel
Remark Link
ID=148

Fabrication and electrochemical properties of cathode-supported solid oxide fuel cells via slurry spin coating

Authors Min Chen, Jing-Li Luo, Karl T. Chuang, Alan R. Sanger
Source
Electrochimica Acta
Volume: 63, Pages: 277–286
Time of Publication: 2012-02
Abstract A cathode-supported SOFC consisting of LSM (La0.8Sr0.2MnO3-δ) cathode supporter, LSM-Sm0.2Ce0.8O2-δ (SDC) cathode functional layer (CFL), yttria stabilized zirconia (YSZ)/SDC bi-layered electrolyte and Ni-YSZ anode layer was fabricated by a slurry spin coating technique. The influence of the porosity in both the CFL and cathode supporter on the electrochemical properties of the cells has been investigated. It was found that properly controlling the porosity in the CFL would improve the performance of the cells using O2 in the cathode side (O2-cells), with a maximum power density (MPD) value achieving as high as 0.58 W•cm−2 at 850 C. However, this improvement is not so evident for the cells using air in the cathode side (air-cells). When increasing the porosity in the cathode-supporter, a significant increase of the power density for the air cells due to the decreasing Rconc,c(concentration polarization to the cell resistance) can be ascertained. In terms of our analysis on various electrochemical parameters, the Ract (activation polarization to the cell resistance) is assumed to be mainly responsible for the impedance arcs measured under the OCV condition, with a negligible Rconc,cvalue being able to be detected in our impedances. In this case, a significant decreasing size of the impedance arcs due to the increasing porosity in the cathode supporter would correspond to a decrease of the Ract values, which was proved to be induced by the decreasingRconc,c.
Keywords Slurry spin coating; Cathode-supported SOFC; Concentration polarization; Activation polarization; Power density
Remark Link
ID=139

Effects of (LaSr)(CoFeCu)O3-δ Cathodes on the Characteristics of Intermediate Temperature Solid Oxide Fuel Cells

Authors Sea-Fue Wang, Chun-Ting Yeh, Yuh-Ruey Wang, Yung-Fu Hsu
Source
Journal of Power Sources
Volume: 201, Pages: 18–25
Time of Publication: 2012-03
Abstract In this study, Cu2+ ions doped La0.6Sr0.4Co0.2Fe0.8O3−δ cathodes are prepared for use in solid oxide fuel cells (SOFCs). The maximum electrical conductivities of the La0.6Sr0.4Co0.2Fe0.7Cu0.1O3−δ (438 S cm−1) and the La0.6Sr0.4Co0.1Fe0.8Cu0.1O3−δ (340 S cm−1) discs are higher than that of the La0.6Sr0.4Co0.2Fe0.8O3−δ disc (LSCF; 81 S cm−1) sintered at 1100 C. The substitution of Cu2+ over Fe3+ leads to a higher coefficients of thermal expansion (CTE), while the replacement of Co3+ by Cu2+ results in a lower CTE. Single cells with the La0.6Sr0.4Co0.2Fe0.8O3−δ, La0.6Sr0.4Co0.2Fe0.7Cu0.1O3−δ, and La0.6Sr0.4Co0.1Fe0.8Cu0.1O3−δ cathodes operating at 650 C and 550 C show similar ohmic resistance (R0) values while the polarization resistance (RP) values of the cells with the La0.6Sr0.4Co0.2Fe0.7Cu0.1O3−δ and a0.6Sr0.4Co0.1Fe0.8Cu0.1O3−δ cathodes are slightly lower than that of the single cell with the La0.6Sr0.4Co0.2Fe0.8O3−δ cathode, indicating that the Cu2+-doped LSCF cathode exhibits a greater electrochemical catalytic activity for oxygen reduction. Maximum power densities of the cells with the La0.6Sr0.4Co0.2Fe0.8O3−δ, La0.6Sr0.4Co0.2Fe0.7Cu0.1O3−δ, and La0.6Sr0.4Co0.1Fe0.8Cu0.1O3−δ cathodes operating at 700 C read respectively 1.07, 1.15, and 1.24 W cm−2. It is evident that the doping of Cu2+ ions in LSCF is beneficial to the electrochemical performance of the cells.
Keywords Solid oxide fuel cell; cathode; cathode; impedance; Cell performance
Remark Link
ID=134

Post-heat treatment pressure effect on performances of metal-supported solid oxide fuel cells fabricated by atmospheric plasma spraying

Authors Chun-Huang Tsai, Chang-sing Hwang, Chun-Liang Chang, Jen-Feng Yu, Sheng-Hui Nien
Source
Journal of Power Sources
Volume: 197, Pages: 145–153
Time of Publication: 2012-01
Abstract The nickel metal-supported cells fabricated by atmospheric plasma spraying are post-heat treated in air at 960 C for 2 h with different pressures. The current–voltage–power and AC impedance measurements show the prepared cell with an applied pressure of 450 g cm−2 in the post-heat treatment has a better electrochemical performance at test temperatures ≥ 650 C. For test temperatures < 650 C, the maximum power densities at 450 g cm−2 pressure are about the same as the maximum power densities at 1250 g cm−2 pressure. The SEM micrograph indicates that the cathode including the cathode interlayer and the cathode collector is the most porous region in the cell. AC impedance results show this cathode is the most sensitive part to the applied pressure in the post-heat treatment and the cell with 450 g cm−2 pressure has the smallest low frequency intercept R2 and the polarization resistance Rp at temperatures from 600 to 800 C. The performance durability test of the cell post-heat treated at 450 g cm−2 pressure shows a degradation rate of 0.0087 mV h−1 or 0.0026 mW h−1 at 300 mA cm−2 constant current density and 750 C test temperature.
Keywords Atmospheric plasma spray; Solid oxide fuel cells; Metal-supported; Nanostructured
Remark Link
ID=121

Solid oxide fuel cells with Sm0.2Ce0.8O2−δ electrolyte film deposited by novel aerosol deposition method

Authors Sea-Fue Wang, Yung-Fu Hsu, Chih-Hao Wang and Chin-Ting Yeh
Source
Journal of Power Sources
Volume: 196, Issue: 11, Pages: 5064-5069
Time of Publication: 2011-06
Abstract In this study, dense electrolyte ceramic Sm0.2Ce0.8O2−δ (SDC) thin films are successfully deposited on NiO-SDC anode substrate by aerosol deposition (AD) with oxygen as the carrier gas at the substrate temperature ranging from room temperature to 300 C. To remove the effect of humidity on the starting powders, this study found that, in depositing SDC films, having the starting powders preheat-treated at 200 C helped generate a smooth and dense layer, though a lower deposition rate was achieved. At a deposition time of 22 min, SDC films with a uniform thickness of 1.5 μm and grain sizes of ≈67 nm are obtained. SOFC single cells are then built by screen printing a LSCF cathode on the anode-supported substrates with SDC electrolyte. The cross-sectional SEM micrographs exhibit highly dense, granular, and crack-free microstructures. The open circuit voltages (OCV) of the single cells decrease with the rise in temperature, dropping from 0.81 V at 500 C to 0.59 V at 700 C. Maximum power densities (MPD) decline with decreasing operating temperature from 0.34 to 0.01 W cm−2 due to the increase of the R0 and RP of the single cells. The electrochemical results testify to the fine quality of SDC films as well as illustrate the electrolyte thickness effect and the effect of mixed ionic and electronic conduction of the SDC electrolyte in the reducing atmosphere.
Keywords SDC films, NiO-SDC substrate, aerosol deposition, Very dense SDC films, uniform thickness of 1.5 μm, Single cell with a MPD of 0.34 W cm−2, 700 C, Solid oxide fuel cell; Ceria; Aerosol deposition; Electrolyte
ID=105

Scandium stabilized zirconium thin films formation by e-beam technique

Authors Darius Virbukas, Giedrius Laukaitis, Julius Dudonis, Oresta Katkauskė and Darius Milčius
Source
Solid State Ionics
Volume: 184, Issue: 1, Pages: 10–13
Time of Publication: 2011-03
Abstract Scandiumstabilizedzirconium (10ScSZ) thin ceramic films were deposited by e-beam evaporation of (ZrO2)0.90(Sc2O3)0.10 micro powder (particle size 0.5 0.7 μm). The influence of deposition rate on formed thinfilms microstructure and electrical properties was studied. 10ScSZ thinfilms were deposited on two types of different substrates: optical quartz (SiO2) and Alloy-600 (Fe–Ni–Cr) substrates. Deposition rate was changed from 2 to 16 /s to test its influence on thinfilmformation and its properties. The microstructure of formed 10ScSZ thin ceramic films was studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Electrical parameters of formed thin ceramics were investigated in the frequency range from 0.1 Hz to 1.0 MHz (in temperature range from 473 to 873 K). The ionic conductivity of the deposited electrolyte 10ScSZ thinfilms was determined by impedance spectroscopy. It was determined that the deposition rate (in range from 2 to 16 /s) has influence on crystallite size. It increases by increasing the deposition rate from 18.4 to 26.9 nm. The XRD measurements show that the formed 10ScSZ thinfilms do not repeat the crystallographic phase of the initial evaporated powder material—it is changes from rhombohedra (initial powder) to cubic (the formed thinfilms).
Keywords Scandium stabilized zirconium (ScSZ); Ionic conductivity; Electron beam deposition; Solid oxide fuel cells (SOFC)
Remark Link
ID=94

The properties of scandium and cerium stabilized zirconium thin films formed by e-beam technique

Authors Darius Virbukas, Giedrius Laukaitis, Julius Dudonis and Darius Milčius
Source
Solid State Ionics
Volume: 188, Issue: 1, Pages: 46–49
Time of Publication: 2011-04
Abstract Scandium and ceriumstabilizedzirconium (10Sc1CeSZ) thin ceramic films were formed evaporating (ZrO2)0.89(CeO2)0.01(Sc2O3)0.10 micro powder using e-beam evaporation technique. The influence of deposition rate on formedthinfilms electrical properties and microstructure was studied. 10Sc1CeSZ thinfilms were deposited on two types of different substrates: optical quartz (SiO2) and Alloy 600 (Fe–Ni–Cr). Deposition rate was changed from 2 to 16 /s to understand its influence on thinfilm formation and other properties. The formed 10Sc1CeSZ thinfilms keep the cubic crystal structure as the initial evaporated powder material but change the main crystallographic peak from (111) to (200) for both types of substrate and used deposition rates. It was determined that the crystallites size increases from 19.0 to 24.9 nm and from 15.6 to 19.9 nm on optical quartz and Alloy 600 respectively by increasing the deposition rate (in range from 2 to 16 /s). The thinfilm density decreases by increasing the deposition rate. The ionic conductivity of 10Sc1CeSZ thinfilms was determined by impedance spectroscopy in the frequency range from 0.1 Hz to 1.0 MHz in temperature range from 473 K to 873 K. The best ionic conductivity σtot = 4.91 10− 2 Sm− 1 at 873 K temperature and the lowest value of activation energy ΔEa = 0.88 eV were found for 10Sc1CeSZ thinfilmsformed at 4 /s deposition rate.
Keywords Scandium and cerium stabilized zirconium (10Sc1CeSZ); Electron beam deposition; Solid oxide fuel cells (SOFC); Ionic conductivity
Remark Link
ID=93

Ethanol internal steam reforming in intermediate temperature solid oxide fuel cell

Authors Stefan Diethelm, Jan Van Herle
Source
Journal of Power Sources
Volume: 196, Issue: 17, Pages: 7355–7362
Time of Publication: 2011-09
Abstract This study investigates the performance of a standard Ni–YSZ anode supported cell under ethanolsteamreforming operating conditions. Therefore, the fuelcell was directly operated with a steam/ethanol mixture (3 to 1 molar). Other gas mixtures were also used for comparison to check the conversion of ethanol and of reformate gases (H2, CO) in the fuelcell. The electrochemical properties of the fuelcell fed with four different fuel compositions were characterized between 710 and 860 C by I–V and EIS measurements at OCV and under polarization. In order to elucidate the limiting processes, impedance spectra obtained with different gas compositions were compared using the derivative of the real part of the impedance with respect of the natural logarithm of the frequency. Results show that internalsteamreforming of ethanol takes place significantly on Ni–YSZ anode only above 760 C. Comparisons of results obtained with reformate gas showed that the electrochemical cell performance is dominated by the conversion of hydrogen. The conversion of CO also occurs either directly or indirectly through the water–gas shift reaction but has a significant impact on the electrochemical performance only above 760 C.
Keywords SOFC; Ni–YSZ anode; Ethanol; Internal reforming; Coking; Impedance spectroscopy
Remark Link
ID=91

Proton Conductivity in Mixed B-Site Doped Perovskite Oxide BaZr0.5In0.25Yb0.25O3−delta

Authors Istaq Ahmed,1,2 Francis G. Kinyanjui,1 Seikh M. H. Rahman,1 Patrick Steegstra,3 Sten G. Eriksson,1 and Elisabet Ahlberg3
Source
J. Electrochem. Soc.
Volume: Volume 157, Issue: Issue 12, Pages: B1819-B182
Time of Publication: 2010-12
Abstract A wet chemical route was used to prepare the oxygen deficient codoped perovskite oxide BaZr0.5In0.25Yb0.25O3−. Analysis of X-ray powder diffraction data showed that the sample belongs to the cubic crystal system with space group Pmm. Dynamic thermogravimetric (TG) analysis confirmed complete filling of oxygen vacancies (V) by protonic defects (OH) during the hydration process. The proton conductivity was investigated by impedance spectroscopy. The bulk and total conductivities of prehydrated BaZr0.5In0.25Yb0.25O3− were found to be 8.510−4 and 2.210−5 S cm−1, respectively, at 300C. The total conductivity in the codoped perovskite oxide was higher compared to that of the respective single doped perovskite oxides with the same doping level. The bulk and grain-boundary mobility and diffusion coefficients of protons were calculated at 200C using impedance and TG data to obtain the conductivity and proton concentration, respectively. The high bulk diffusivity (2.310−7 cm2 s−1) was obtained which indicates that the protons are more free to move in the heavily doped matrix compared to the lightly doped systems where trapping of protons occurs.
Keywords barium compounds, proton exchange membrane fuel cells, thermal analysis, vacancies (crystal), X-ray diffraction, zirconium compounds
Remark Link
norecs.com

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