bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced Chromium Tolerance of La0.6Sr0.4Co0.2Fe0.8O3-δ Cathode by BaO Infiltration
Authors: Chen Kongfa , Ai Na , Jiang San Ping
Published: July 2015

Performance degradation of cathodes due to the attack by chromium from Fe-Cr alloy interconnect is a major barrier to develop long-term durable solid oxide fuel cells (SOFCs). In this presentation, we report the development of a chromium tolerant BaO infiltrated La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathode. After the test at 800oC for 100 h in the presence of Fe-Cr interconnect, the electrode polarization resistance (RE
) of the infiltrated BaO-LSCF electrode increases by 0.05 Ω cm2, much smaller than 0.48 Ω cm2 in the case of the LSCF electrode. The presence of BaO nanoparticles inhibits the formation of SrCrO4 by forming thermodynamically stable and conducive BaCrO4, thus preventing the extraction of Sr at the A-site of LSCF perovskite structure and mitigating the poisoning effect of Cr on the electrocatalytic activity of LSCF. The results have demonstrated a new and effective strategy to develop highly tolerant and resistant cathodes towards the Cr contaminant of SOFCs.
Annealing-Induced Surface Segregation and SrSO4 Formation on La0.6Sr0.4Co0.2Fe0.8O3
-δ
Cathodes
Authors: Bagarinao Katherine Develos- , De Vero Jeffrey Centeno , Cho Do-Hyung , Kishimoto Haruo , Yamaji Katsuhiko , Horita Teruhisa , Yokokawa Harumi
Published: July 2015

Dense LSCF thin films having controlled surfaces were epitaxially grown using pulsed laser deposition (PLD) on gadolinia-doped ceria (GDC) films with (100), (110), and (111) orientations, and then subjected to long-term annealing at 800°C and 900°C in air for 1-3 months. Detailed microstructural characterizations revealed preferential surface segregation for LSCF thin films which were epitaxially grown on (110) and (111)-oriented GDC films whereas this appears mostly inhibited for LSCF thin films on (100)-oriented GDC. Compositional and structural analyses revealed that the surface-segregated crystallites are SrSO4 in origin, which is attributed to the reaction of the segregated Sr cations from LSCF with SO2 present in the air. Furthermore, SrSO4 formation on LSCF surfaces was accompanied by coarsening and granularization of the LSCF layer. These results have implications toward tailoring the performance of cathode surfaces by understanding the dependence of cation segregation on driving forces such as surface chemistry and microstructure.
Sulfur Poisoning of LSCF Cathode in Single Step Co-fired SOFC
Authors: Mori Naoya , Sato Yosuke , Iha Michiaki , Takada Takahiro , Konoike Takehiro , Kishimoto Haruo , Yamaji Katsuhiko , Yokokawa Harumi
Published: July 2015

Murata Manufacturing Co., Ltd. has been developing single step co-fired planar type solid oxide fuel cells (SOFCs). A long-term operation had been carried out at 750°C for over 8000 h under galvanostatic condition. The single cell voltage degradation rate was less than 0.20 %/kh after 2000 h operation, and Cr-poisoning in the LSCF cathode after 10000h operation was not observed. However sulfur distribution in the La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) cathode was observed by detailed analysis. To study the S- poisoning mechanism, SO2 poisoning test was carried out at various temperatures, current density and air utilization (Ua). As a result, it revealed that the distribution of sulfur depended on the operating temperature, current density and Ua.
Mechanism of SO2 Poisoning on the Electrochemical Activity of LSCF and LSM Electrodes
Authors: Wang ChengCheng , Jiang San Ping
Published: July 2015

Sulfur in the air stream is one of the major contaminants affecting the performance stability of cathodes of solid oxide fuel cell (SOFCs) such as La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) and La0.8Sr0.2MnO3 (LSM) perovskite oxide. In this paper, the effects of operating temperatures and SO2 concentrations on the electrochemical performance of LSCF and LSM cathodes are investigated. Sulfur poisoning effect is more pronounced at lower temperatures for LSM and LSCF cathodes, i.e., 700 oC. Sulfur deposition occurs inside the LSCF electrodes according to TOF-SIMS result and is most pronounced on the surface of LSCF at 700 oC, forming primarily SrSO4. For LSM, sulfur deposition is more obvious on the interface of LSM/YSZ at 800 oC by Nano-SIMS result. The reaction mechanism between sulfur dioxide and LSCF and LSM electrodes is then discussed.
Influence of Cathode Polarization Change on Chromium Deposited on Electrolyte Surface Near Cathode Reaction Sites of SOFC
Authors: Ishibashi Daiki , Park Eunjoo , Taniguchi Shunsuke , Inoue Yuko , Chou Jyh-Tyng , Sasaki Kazunari
Published: July 2015

It has been clarified that Cr deposition occurs significantly on the electrolyte surface near cathode reaction sites as a consequence of cathode polarization. In this study, we investigated the influence of a change in the cathode polarization on the Cr deposited on the electrolyte surface by using NiO/YSZ or NiO/GDC as the cathode material. The deposited Cr segregated at the interface of NiO and YSZ in the case of the NiO/YSZ cathode after a decrease in the cathode polarization, which suggests nucleation under a cathode polarization of 200 mV and growth of Cr compounds after decreasing the cathode polarization. In contrast, the amount of deposited Cr decreased in the case of the NiO/GDC cathode after decreasing the cathode polarization.
Effect of Chromium Vapor Pressure on Accelerated Poisoning Tests for (La0.6Sr0.4)(Co0.2Fe0.8)O3 Cathode
Authors: Cho Do-Hyung , Bagarinao Katherine Develos- , Kishimoto Haruo , Yamaji Katsuhiko , Horita Teruhisa , Yokokawa Harumi
Published: July 2015

In our previous studies on chromium (Cr) poisoning, Cr metal covered with Cr2O3 was directly placed on the current collector of the cathode as a source of Cr vapor. However, the performance degradation is accelerated in surplus in the setting of the Cr source. In order to perform accelerated poisoning test at an appropriate rate, we improved the cell operating equipment to control the Cr vapor pressure during the cell tests. The Cr vapor pressure was controlled by adjusting the place and temperature of the Cr source. The Cr poisoning tests were operated at 1073 K under controlled feeding rate of Cr vapor after the cell performance became stable. The degradation rate decreased by improving the setting to decrease the Cr vapor pressure, and the amount of Cr species deposited in LSCF cathode was also reduced with decreasing the Cr vapor pressure.
Thermal Gradients in Solid Oxide Fuel Cell Anodes: X-Ray Diffraction, Thermal Imaging and Model Prediction
Authors: Robinson James B. , Engebretsen Erik , Brown Leon D , Clague Ralph , Eastwood David , Reinhard Christina , Lee Peter , Brett Dan J. , Shearing Paul R.
Published: July 2015

Thermal gradients can be induced within solid oxide fuel cells (SOFC) due to a range of design and operational considerations. These gradients coupled with the mismatched coefficient of thermal expansion between the anode and electrolyte layer can advance cell degradation and lead to cell failure. In this study a combined experimental and modelling approach is taken to investigate the effect of thermal gradients on the stresses within SOFC anodes. Experimental results obtained from investigations performed at Diamond Light Source using a concurrent X-ray diffraction and infrared thermal imaging approach are coupled with finite element analysis modelling to assess the impact of various parameters upon the cell. Operational considerations including cell polarisation and fuel flow configurations are examined to demonstrate the importance of optimization in minimising thermal gradients and subsequent stresses within the anode to prolong the lifetime of the cell whilst also maintaining the performance of the cell.
In-Operando Raman Spectroscopy Study on Oxygen Chemical Potential Gradient in Ni-SDC Cermet Anode for SOFCs
Authors: Matsui Toshiaki , Eguchi Kohei , Furukawa Takeshi , Okanishi Takeou , Muroyama Hiroki , Eguchi Koichi
Published: July 2015

The cermet of Ni‒oxide ion conductor is widely used as an anode in SOFCs. However, the usage of nickel induces various degradation phenomena during discharge operation; e.g., agglomeration and/or oxidation of nickel catalyst, and carbon deposition. In most cases, these degradation phenomena are triggered by the variation in the oxygen chemical potential inside the anode. In this study, then, in-operando Raman spectroscopy was conducted for Ni−SDC (Ni−Ce0.8Sm0.2O2-δ
) cermet anode at 700ºC with applying SDC as a probe for the detection of oxygen chemical potential. This is because the band related to oxygen vacancy in the Raman spectrum of SDC changes depending on the partial pressure of oxygen in the ambient atmosphere. The variation in oxygen chemical potential at the top surface of anode was successfully quantified. The effective reaction zone of anode was also discussed comparing with the data estimated from impedance spectra.
In Operando Optical Studies of SOFCs Operating with Butanol
Authors: Kirtley John D. , Pomfret Michael B , Steinhurst Daniel A , Owrutsky Jeffrey C , Walker Robert A
Published: July 2015

In operando optical methods coupled with electrochemical measurements were employed to explore the effects of dry and humidified butanol on the performance and durability of anode supported Ni-YSZ membrane electrode assemblies in functioning solid oxide fuel cells (SOFCs). In order to assess directly the effects of butanol in SOFCs operating at 700˚C and 800˚C, near-infrared thermal imaging was used to measure temperature gradients across the anode while vibrational Raman spectroscopy quantified the tendency for carbon to accumulate in different regions of the anode. FTIR emission spectroscopy monitored gas phase composition above the anode and identified adsorbed surface intermediates. Butanol reforming led to modest cooling (DT = -4˚C) of the anode at OCV. Humidifying the fuel mitigated this effect slightly (DT ~ -2˚C). Polarizing the cell had very little effect on anode temperature changes that resulted from endothermic fuel surface reactions. Within the high temperature environment of the SOFC, butanol underwent significant gas phase reforming with methane, ethylene, formaldehyde and carbon monoxide all being observed in the SOFC fuel exhaust. This heterogeneous mixture led to substantial carbon accumulation on the anode observed in operando, Subsequent studies, however, indicated that carbon distribution was very heterogeneous in the anode microstructure. Post mortem, ex situ experiments showed that heterogeneity in carbon accumulation extended both across and through the anode microstructure with the highest concentration of surface carbon closest to the fuel inlet. Polarizing the cell slowed, but did not prevent, carbon from forming under a neat butanol feed, but humidifying the butanol suppressed carbon formation completely.
Phase Transition Mapping by Means of Neutron Imaging in SOFC Anode Supports during Reduction under Applied Stress
Authors: Makowska Malgorzata Grazyna , Strobl Markus , Mejdal Lauridsen Erik , Frandsen Henrik Lund , Tremsin Anton , Shinohara Takenao , Kuhn Luise Theil
Published: July 2015

Mechanical and electrochemical performance of layers composed of Ni-YSZ cermet in solid oxide fuel and electrolysis cells (SOC) depends on their microstructure and initial internal stresses. After sintering the manufacturing conditions, i.e. temperature, atmosphere and loads, can influence the microstructure and in particular the internal stresses in the Ni-YSZ layer and thereby the cell performance. Spatially resolved observation of the phase transition during reduction can provide information on how parameters like temperature and external load influence the reaction progress. This information is crucial for optimization of the SOC performance. In this work the measurements with energy resolved neutron imaging of the phase transition during the NiO-YSZ reduction performed at different temperatures with and without applied load, are presented. The results indicate a link between reduction rate and stress, which will influence the initial stress field of the SOC stacks.
Visualization of SOFC Anode by Dual Imaging Method Using Infrared and Visible Light Cameras
Authors: Tachikawa Yuya , Kawabata Tsutomu , Shiratori Yusuke , Sasaki Kazunari
Published: July 2015

Thermography imaging can be applied for the surface of an SOFC electrode to evaluate the spatial distribution of reforming and electrode reactions. For getting a correct temperature distribution by thermography, emissivity change on the object surface caused by chemical reactions or material coverage must be precisely evaluated. In-situ observation using both infrared and visible light dual cameras enables us to obtain precise emissivity change and thus temperature distribution, because the influence of emissivity change can be corrected by the visible light imaging technique. In this study, this imaging method is applied for an anode material which was exposed to a fuel flow causing coke formation, and the information on the carbon distribution was successfully separated on the anode surface to obtain the true temperature distribution.
In Situ Tailored Nickel Nano-Catalyst Layer for Internal Reforming Hydrocarbon Fueled SOFCs
Authors: Myung Jaeha , Neagu Dragos , Tham Mark , Irvine John T. S.
Published: July 2015

Conventional Ni cermet anodes suffer from carbon deposition when they are directly used with hydrocarbon fuels due to the negative effects of pyrolysis and Boudouard reactions. In this work, the use of a non-stoichiometric perovskite, La0.8Ce0.1Ni0.4Ti0.6O3, as a reforming layer in reducing atmospheres led to the surface being highly populated with homogeneously exsolved Ni nano particles. This catalyst layer was applied to Ni-GDC anode supported and ScSZ electrolyte supported cells to prevent carbon deposition and to stabilize operation with dry methane. The catalyst layer showed both excellent attachment to the Ni-GDC anode and resistance to carbon deposition. The performance of the Ni–GDC anode-supported cells with the catalyst layer was about 1.1 W/cm2 in hydrogen fuel which is similar to that seen without the use of a catalyst layer. For the ScSZ electrolyte supported cells, the catalyst layer improved the power density and stability when in operation with dry methane.
Electrochemical Oxidation of CO/H2 Mixtures on Ni and Ceria Pattern Anodes
Authors: Tabish A.N. , Patel Hrishikesh C , Comelli Filippo , Aravind P.V.
Published: July 2015

Electrochemical oxidation of dry CO/H2 mixtures on symmetrical Ni and ceria pattern anodes on YSZ electrolyte has been examined between 700-850 oC. Dry environment was used to exclude the possible side reactions like water-gas-shift (WGS) in the case of CO and CO/H2 mixtures. Electrochemical impedance spectroscopy (EIS) shown 2.5 times higher polarization resistance for pure CO as compared to that of pure H2 for Ni anodes and 5 times higher in case of ceria anodes. With the addition of small quantities of H2 in CO, the polarization resistance dropped drastically. For all considered mixtures the size of impedance arc was closer to that of pure H2 as compared to that of pure CO. The activation energies obtained by equivalent circuit model (ECM) fitting of impedance spectra were similar to that of pure H2 clearly indicating that H2 is preferentially oxidized.
Kinetics of Internal Methane Reforming on the Anodes of Low Temperature Ceres Power Steel Cell SOFCs
Authors: Leah Robert Timothy , Lankin Mike , Bone Adam , Mukerjee Subhasish , Selby Mark
Published: July 2015

Ceres Power has developed a unique low-temperature metal supported SOFC design (the ‘Steel Cell’) based predominantly around the use of ceria. This unique design architecture offers greatly enhanced robustness to real-world operating conditions at a lower cost than conventional SOFC designs, whilst retaining the advantages of fuel flexibility, high efficiency and low degradation. A widely quoted benefit of SOFCs is the ability to carry reforming of hydrocarbon fuels to syngas within the anode of the cells, simplifying the design of the fuel processing system. A perceived disadvantage of low temperature SOFC operation is that significant levels of internal methane reforming are no longer possible due to poor kinetics and thermodynamically limited methane conversion. The Ceres steel cell technology has been developed and demonstrated to perform high levels (40-60%) of internal methane reforming. In this paper a method for approximately estimating the kinetics of methane reforming on Steel Cell anodes will be described, coupling experimental measurements to a mathematical model.
Impedance Studies of the Reduction Process in NiO-YSZ SOFC Anodes
Authors: Vladikova Daria , Stoynov Zdravko , Wuillemin Zacharie , Montinaro Dario , Piccardo Paolo , Genov Ivaylo , Rolland Mélanie
Published: July 2015

The aim of this study is the development of a methodology for deeper insight into the Ni-YSZ anode behavior by in situ impedance monitoring of the Ni network initial formation and changes during the redox process. The testing is performed on single bare anodes. This approach bypasses complications arising from the impedance data analysis of cells. For more complete description of the changes in the anode microstructure, gas permeability measurements are also introduced. The obtained results show that impedance can register the changes in the sample’s conductivity during anode reduction, as well as during redox cycling performed in mild oxidation conditions. The oxidation rate is much slower than the reduction one. The combination of impedance with gas permeability and microstructural measurements gives new opportunities for anode optimization in respect to the ohmic and the concentration polarization.
Kinetic Studies on Ni-YSZ Composite Electrodes
Authors: Njodzefon Jean-Claude , Sudireddy Bhaskar Reddy , Hjelm Johan , Graves Christopher
Published: July 2015

AC and DC techniques were applied to investigate the electrochemical reaction kinetics of porous composite Ni/8-mol% yttria-stabilized zirconia (Ni/8YSZ) solid oxide cell (SOC) electrodes using a novel pseudo-3-electrode cell geometry. From OCV impedance spectra an activation energy Ea
of 1.13 eV, pre-factor γan
of 3.7∙105∙T, hydrogen and steam partial pressure dependencies a and b respectively of -0.07 and 0.22 were determined. DC current density vs. overpotential curves compared with those predicted using the determined kinetic parameters. Apparent Butler-Volmer charge transfer coefficients α were determined from the current density vs. overpotential curves. Values ranging from 0.57 at 650 °C to 0.64 at 850 °C were determined from the anodic branch and 0.85 to 0.81 from the cathodic branch in the same range, with higher fitting accuracy in the anodic branch. The lower fitting accuracy of the cathodic branch and the need for different α values for each branch suggests that a simple BV model of the measured electrode kinetics is insufficient and/or different reaction mechanisms might be occurring in anodic vs cathodic polarization.
Study of Water Gas Shift Reaction over Ceria Based Catalysts in Solid Oxide Fuel Cells
Authors: Tepamatr Pannipa , Buarod Eumporn , Laosiripojana Navadol , Charojrochkul Sumittra
Published: July 2015

Production of hydrogen with low CO concentration from ethanol steam reforming for use in a solid oxide fuel cell has been studied. As Ni/Ceria can be used as an anode for intermediate temperature SOFC, the capability in a water gas shift reaction will enhance the performance even further from a steam reforming reaction. The preparation method of Ni supported ceria based catalysts for water gas shift reaction is taken into consideration. The structural properties, particle size changes, reducibility and the microstructure of the catalysts are investigated using X-ray diffraction, temperature-programmed reduction and scanning electron microscopy as well as the performance investigation.
Impregnation of Nanoparticle Scaffolds for Syngas-Fed Solid Oxide Fuel Cell Anodes
Authors: Boldrin Paul , Ruiz-Trejo Enrique , Tighe Christopher , Chang Kee-Chul , Darr Jawwad , Brandon Nigel P.
Published: July 2015

A strategy for fabrication of solid oxide fuel cell anodes with improved porosity and lower sintering temperatures by impregnation of nanoparticle-containing porous scaffolds of ceria-gadolinia (CGO) has been developed. The CGO scaffolds are fabricated using a screen-printed ink containing nanoparticles and commercial particles of CGO and polymeric pore formers. Scanning electron microscopy and in situ ultra-small angle X-ray scattering show that incorporation of nanoparticles increases the porosity by allowing a reduction in sintering temperature. Electrochemical characterisation of symmetrical cells shows that the cells sintered at 1000 °C possess similar electrode polarisation compared to those sintered at 1300 °C. Button cell testing showed that reducing the sintering temperature produced cells which perform better at 700 °C and below in hydrogen, and performed better at all temperatures using syngas. This approach has the potential to allow the use of a wider range of nanomaterials, giving a finer control over microstructure.
The Influence of Reduction Conditions on a Ni-YSZ SOFC Anode Microstructure and Evolution
Authors: Monzón Hernán , Laguna-Bercero Miguel Angel
Published: July 2015

Ni-YSZ cermets are the most widespread material used as SOFC anodes. These materials are generally fabricated through the reduction of a NiO-YSZ composite, but the reduction conditions have a great effect in the final microstructure of the electrode. In the present work several conditions were explored to reduce microtubular anode supports produced via extrusion in order to find a suitable microstructure for SOFC anodes. Samples were reduced in pure and diluted H2, either dry or humidified at temperatures ranging from 400 to 800°C while their DC conductivity was being monitored. The highest value of peak conductivity was measured in the sample reduced in humidified pure hydrogen at 800°C, but it experienced more severe conductivity degradation that other samples. The best value for the duration of the test was obtained for the sample reduced in dry diluted hydrogen at 800°C.
Stability of Nickel-Infiltrated Anodes in Intermediate Temperature SOFCs
Authors: Miller Elizabeth C , Sherman Quentin , Gao Zhan , Voorhees Peter W , Barnett Scott A
Published: July 2015

Nickel-infiltrated La1-xSrxGa0.8Mg0.2O3-δ (LSGM) anode functional layers have been shown to yield low polarization resistance in intermediate-temperature solid oxide fuel cells (IT-SOFCs) with thin LSGM electrolytes. A dehydration step after nickel nitrate infiltration and a decrease in the calcination temperature were both shown to decrease the initial NiO particle size, but other factors such as geometry and Ni loading affected the Ni particle size upon reduction. The infiltrated anode polarization resistance, measured during life tests of full cells by separating out the anode component using electrochemical impedance spectroscopy and equivalent circuit fitting, increased continuously, e.g. from 0.08 to 0.16 W cm2, after 550 h at 650°C. This change was accompanied by approximately a factor of 2 increase in the feature size of the infiltrated Ni. A simple electrochemical model is presented that predicts the observed changes in polarization resistance based on the effect of particle coarsening on triple-phase boundary density.
Boundary Observation and Contrast Tuning of Ni/YSZ Anode by TEM and FIB-SEM
Authors: Liu Shu-Sheng , Matsumura Syo , Koyama Michihisa
Published: July 2015

Ni/yttria stabilized zirconia (Ni/YSZ) anode was investigated in the aspect of microstructure. Atomic resolution transmission electron microscopy and high resolution focused ion beam-scanning electron microscopy (FIB-SEM) were used to study the atomic structure of boundaries and phase contrast, respectively. Images of Ni/YSZ interface and Ni/YSZ/pore triple-phase boundary were obtained. High-Index contact surfaces were found. Distinct phase contrast among Ni, YSZ and resin was observed during the slice and view process in FIB-SEM.
Residual Stress in NiO-YSZ Composites and Its Relationship to Microstructure
Authors: Akaza Yoshiki , Syu Takaho , Iguchi Fumitada , Shimizu Makoto , Yugami Hiroo
Published: July 2015

Residual stress in NiO-YSZ was numerically simulated using 2D models consisted of the arrays of NiO and YSZ particles to evaluate the influence of thermal stress due to the large difference of thermal expansion coefficient between NiO and YSZ. The influence of geometric microstructure changed by fabrication processes was also evaluated using the models with different arrangements. Numerical simulation revealed that thermal strain introduced from the hetero interfaces was canceled each other, and residual stress in a uniform model was small. But, in ununiformed models, residual stress increased because counterpart stress was absence at homo interfaces due to ununiformity. Simulation results also indicated that a part of particles near the interfaces was exposed to high residual stress as reaction forces to thermal stress.
Overpotential and Interfacial Conductivity of Ni/YSZ Anode Based on Species Territory Adsorption Model in SOFCs
Authors: Nagasawa Tsuyoshi , Hanamura Katsunori
Published: July 2015

Overpotential and interfacial conductivity of Ni/YSZ anode in SOFCs were investigated under the conditions of various fuel compositions, based on a new reaction model around Triple Phase Boundary (TPB), in which hydrogen and oxygen atoms was assumed to be adsorbed on surfaces of Ni and YSZ, respectively, which was a “species territory adsorption model”. Through the model, the anode overpotential was explicitly expressed as a function of current density continuously from low to high sides and the interfacial conductivity of anode at equilibrium potential could be obtained analytically. The analytical results of anode overpotential were independent of hydrogen partial pressure at low current density region, while increased with decreasing hydrogen partial pressure at high current density region. Moreover, the interfacial conductivity as a function of water vapor pressure had a maximum value in the range of P
H2O=0.15-0.25 atm. The analytical results agreed well with experimental ones.
Understanding the Rheology of Screen-Printing Inks for the Fabrication of SOFC Thick Films
Authors: Somalu Mahendra R. , Muchtar Andanastuti , Brandon Nigel P.
Published: July 2015

Fabrication of SOFC components by screen-printing using an optimized ink is very significant for the production of high quality films with improved performance. Understanding the correlation between the composition and rheology of the inks may enhance the properties screen-printed films. In this study, the rheological properties of NiO/ScSZ anode inks were studied and correlated to the particle network strength, screen-printability and film properties. All the inks were fabricated using a triple roll mill. The dynamic study showed that inks having particle network strength and complex modulus in the range of 50-200 Pa and 500-4000 Pa, respectively, were determined suitable for screen-printing application. In addition, these inks showed suitable viscosity and thixotropy with acceptable tackiness for screen-printing application. This range was exhibited by inks having binder and solids loading in the range of 1-3 wt% and 25-30 vol%, respectively. Furthermore, films fabricated using these inks showed improved particle connectivity, mechanical hardness, electrical and electrochemical performance resulting from increased particle connectivity.
Evaluation of Ni-YSZ Anode Degradation during Redox Cycling
Authors: Shimura Takaaki , Jiao Zhenjun , Hara Shotaro , Shikazono Naoki
Published: July 2015

Degradation of Solid Oxide Fuel Cell (SOFC) anode under redox cycling was evaluated by microstructure change measurements and overpotential calculations using a Lattice Boltzmann method (LBM). Microstructures were obtained by Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) reconstruction technique. In the overpotential calculation, exchange current density and Yttria stabilized Zirconia (YSZ) ionic conductivity were considered as degradation factors. Numerical simulation reproduced well the decrease of overpotential just after the redox treatment and the increase after subsequent discharge process. This is consistent with the experimental result. However, simulation result showed lower overpotential values than the experiment after 10 redox cycles. Deterioration of exchange current density and YSZ ionic conductivity are considered as the reason for the degradation after redox cycles.
Oxidation-Induced Degradation of SOFC Ni Anodes at High Fuel Utilizations
Authors: Kawasaki Tatsuya , Sugimoto Junki , Tachikawa Yuya , Shiratori Yusuke , Taniguchi Shunsuke , Sasaki Kazunari
Published: July 2015

In the downstream of SOFC systems, higher oxygen partial pressure can cause oxidation-induced Ni anode degradation. In this study, we have investigated cell performance at high fuel utilizations for simulating situations around the system downstream. When the anode voltage was higher than a voltage threshold, the cell performance was stable. On the other hand, it became unstable associated with cell voltage oscillation when anode voltage was around or less than the threshold value. The threshold value was consistent with the anode potential derived from the oxygen partial pressure at the phase boundary at which both Ni and NiO coexist.
Performance Factors and Sulfur Tolerance of Metal Supported Solid Oxide Fuel Cells with Nanostructured Ni:GDC Infiltrated Anodes
Authors: Nielsen Jimmi , Sudireddy Bhaskar Reddy , Hagen Anke , Persson Åsa Helen
Published: July 2015

Two metal supported solid oxide fuel cells (active area 16 cm2) with nanostructured Ni:GDC infiltrated anodes, but different anode and support microstructures were studied in respect to sulfur tolerance at the aimed operating temperature of 650ºC. The studied MS-SOFCs are based on ferretic stainless steel (FeCr) and showed excellent performance characteristics at 650ºC with area specific resistances (ASR) of 0.35 Ωcm2 and 0.7 Ωcm2 respectively. The sulfur tolerance testing was performed by addition/removal of 2, 5, and 10 ppm H2S in hydrogen based fuel under galvanostatic operation at a current load of 0.25Acm-2. The results were compared with literature on the sulfur tolerance of the conventional SOFC Ni/YSZ cermet anode. The comparison in terms of absolute cell resistance increase and relative anode polarization resistance increase indicate, that the nanostructured Ni:GDC MS-SOFC based anode is significantly more sulfur tolerant than the conventional Ni/YSZ cermet anode.
The Influence of Sulfur Poisoning and YSZ Substrate Orientation on Electrochemical Properties of Nickel Pattern Anodes
Authors: Doppler Michael Christoph , Fleig Jürgen , Opitz Alexander Karl
Published: July 2015

Micro-patterned Ni thin films with well-defined 2D-structures are useful to examine electrochemical reaction kinetics of SOFC anodes. In this work, an electrode preparation method is developed yielding stable Ni pattern electrodes on YSZ, which facilitate long term measurements. Moreover, these stable electrodes allowed investigating the effect of the YSZ substrate orientation on the polarization resistance and interface capacitance. Statistical analysis of data obtained from 3 different substrates revealed no significant difference in polarization resistances and no significant difference in interface capacitance between single crystalline substrates (α=0.05). Also, the effect of hydrogen sulfide on the polarization resistance was examined and the results are qualitatively equivalent to findings on cermet electrodes.
Performance Recovery of Sulfur Poisoning Anode and Prevention of Sulfur Poisoning by Shifting Anode Potential for Solid Oxide Fuel Cell
Authors: Yamada Yuki , Okubo Ryosuke , Kinoshita Masahiro , Yoshinaga Masashi , Niwa Eiki , Hashimoto Takuya , Tomomichi Keita , Sasaki Kazuya
Published: July 2015

The possibility of performance recovery of the sulfurated Ni-yttria stabilized zirconia anode electrode by shifting the anode electrode potential to the stable region, in which nickel exists as metal, is investigated. The effect of controlling the potential of the anode electrode to the stable region to suppress the generation of nickel sulfide is also revealed. The surface of Ni particle reacts with sulfur to form Ni3S2 in a low temperature region; however, the nickel is reduced to metallic by shifting the electrode potential to –1.9 V vs reference electrode exposed to O
2– When the potential of the Ni-based anode electrode is maintained at the value of ≤ -1.9 V vs the reference electrode potential, the sulfidation of nickel is inhibited.
Li/Na Modified Ni-SDC Anode for Methane-Fueled Solid Oxide Fuel Cells
Authors: Liu Lilu , Yang Qi , Yang Wei , Qi Xingguo , Sun Chunwen , Chen Liquan
Published: July 2015

A facile chemically lithium/sodium insertion method has been developed to prepare Li/Na modified-NiO composites (Li/Na-NiO). The single cells were fabricated with a Li/Na modified NiO-Ce0.8Sm0.2O1.9 (SDC) composite anode screened on a 300µm La0.9Sr0.1Ga0.8Mg0.2O3-δ(LSGM) electrolyte and a composite cathode consisting of Sr0.95Ce0.05CoO3-δ
and SDC (30wt%). The cells with Li/Na modified Ni-SDC anode material deliver much higher open circuit voltages (OCV) than that of the cell with pure Ni-SDC anode. When wet CH4 was used as fuel, the peak power densities of the cells with the Li and Na modified Ni-SDC anode reach about 212mW cm-2 and 231mW cm-2
at 800oC, respectively, which were much higher than that with the pristine Ni-SDC anode. In addition, the cells with Li/Na modified Ni-SDC anode materials show better long-term stability at 800oC. The preliminary results demonstrate that the Li/Na modified Ni-SDC anode materials are promising alternative anode for hydrocarbon-fueled solid oxide fuel cells.
Fabrication of a Ni/MgO Nanocomposite Catalyst by Exolution
Authors: Lim Ye Sol , Yoon Jong Seol , Choi Byung Hyun , Seo Won Seon , Hwang Hae Jin
Published: July 2015

A Ni(NixMg1-x)O nanocomposite catalyst was fabricated by exsolution technique from a (NixMg1-x)O solid solution powder. On reduction, Ni2+ ion close to the surface exsolved as nano particles, which were homogeneously distributed in the matrix powder surface. TEM observation suggested that the exsolution occurred preferentially at the edge surface of the matrix powder. The methane partial oxidation and hydrogen selectivity over the nanocomposite catalysts were evaluated over the temperature range, 300 to 900ºC.
Investigation of Novel Electrocatalysts for Metal Supported Solid Oxide Fuel Cells - Ru:GDC
Authors: Sudireddy Bhaskar Reddy , Nielsen Jimmi , Thydén Karl Tor Sune , Persson Aasa Helen , Brodersen Karen
Published: July 2015

The electrochemical performance and stability of the planar metal supported solid oxide fuel cells (MS-SOFC) with two different electrocatalytically active materials, namely, Ni:GDC and Ru:GDC was investigated. Ru:GDC with an ASR of 0.322 Ωcm2 performed better compared to Ni:GDC with an ASR of 0.453 Ωcm2 at 650oC. The performance of the Ru:GDC infiltrated MS-SOFC is the best measured so far on planar MS-SOFCs. It was observed that the stability of both the electrocatalytically active materials is relatively poor. Microstructure of the anode functional layer appeared to be dense up on the examination. Further optimization of microstructure, electrocatalyst amount and electrocatalyst integration process can improve the long-term stability in particular and electrochemical performance in general.
Nickel Doped Lanthanum Chromite Perovskite: A Novel Regenerable Anode Material for Solid Oxide Fuel Cells
Authors: Sun Yi-Fei , Wang Meng-Ni , Luo Jing-Li
Published: July 2015

A series of nickel doped lanthanum strontium chromite (La0.7Sr0.3Cr1-xNixO3-y, x=0.05-0.3) perovskite anodes for SOFCs was fabricated by glycine combustion method. The structural properties and electrochemical performances of the anode materials were investigated. It was found that the materials with various nickel dopant contents showed an orthorhombic perovskite phase. However the formation of parasitic phase of NiO could also be detected for the material with nickel content >20%. Thermogravimetric analysis (TGA) measurement performed in 5% H2-N2 showed that the mobility of oxygen in the materials increased with the increase of Ni content. For La0.7Sr0.3Cr0.8Ni0.2 (LSCNi) sample, Scan Electron Microscope (SEM) images detected the in-situ growth of nano Ni particles with the average diameter of 20 nm anchoring on surface of the material after the exposure in reducing atmosphere. The material with exsolution of Ni nano particle displayed improved power density output and reduced the activation polarization resistance compared to pure La0.7Sr0.3CrO3-y (LSC).
Chemical Compatibility of A-site Deficient La Substituted SrTiO3
Anode and Stabilized Zirconia Electrolyte
Authors: Chen Gang , Luo Yifei , Gao Yu , Guo Ruifeng , Ma Wanqing , Liu Man , Geng Shujiang
Published: July 2015

To investigate the chemical compatibility of A-site deficient LST anode and stabilized zirconia electrolyte, (La0.25Sr0.75)xTiO3 (x=0.86, 0.88, 0.885, 0.887 and 0.89) powders were prepared by sol-gel method. TiO2 precipitated in each LST sample except LST-0.89. The amount of TiO2 precipitated in A-site deficient LST increased with the increasing of A-site deficiency concentration. Phase change of as-prepared LST and ScSZ composite pellets after annealed at 1200 oC in air was characterized by XRD. Diffusion of Ti from LST into ScSZ at elevated temperature was enhanced with the increasing of TiO2 precipitated in LST. Diffusion of Zr and Sc from ScSZ into LST occurred in LST-0.89/ScSZ, LST-0.887/ScSZ, LST-0.885/ScSZ and LST-0.86/ScSZ pellets. No obvious phase change was observed in LST-0.88/ScSZ, hence LST-0.88 was considered to possess relatively good chemical compatibility with ScSZ.
Performance and Redox-stability of La and Ni Co-doped SrTiO3 Anode of Solid Oxide Fuel Cell
Authors: Park Byung Hyun , Choi Gyeong Man
Published: July 2015

Conventional Ni-cermet anodes show problems for the stability due to carbon coking or Ni coarsening etc.. Perovskite oxides are good candidates as an alternative anode. Electro-catalytic nanoparticles such as Ni or Ru can be produced in oxide anodes when exposed to reducing atmosphere. In this study, we have studied the performance of La0.2SrxTi0.9Ni0.1O3-δ anodes with different Sr content (x=0.7 or 0.8). La0.2Sr0.7Ti0.9Ni0.1O3-δ (LS27) was also composited with Gd0.2Ce0.8O2 (GDC) and impedance spectra and power measurement of the cells with the composite anodes have shown the redox stable and excellent performance of the cell with LS27-GDC anode.
Characterization of Y-Doped SrTi1-XVxO3 (Y = 0.1, x = 0.1 and 0.2) Anodes for SOFCs
Authors: Mohammed Basheer Mohamad Firdaus , Ming Lim Chee , Petra Pengiran Iskandar , Azad Abul Kalam
Published: July 2015

Substitution of Vanadium at the B site of perovskite is believed could be the potential solution to the limitation that Y-doped SrTiO3 is currently facing. Y-doped SrTi1-xVxO3 (Y=0.1 and X=0.1 and 0.2) were selected as the materials under this investigation and all measurements were carried out under normal atmospheric pressure. The experimental data shows that both samples exhibit tetragonal crystal structure with space group I 4/m c m and satisfies anode requirement in terms of porosity. The TEC values reported for these materials are closed to the TEC value of YSZ (10.8 x 10-6 K-1). The measured electrical conductivity is in the order of 0.002 Scm-1 to 0.2042 Scm-1 at the temperature range between 600°C to 1000°C. TG analyses of the samples have shown significant weight loss for Sr0.9 Y0.1 Ti0.9 V0.1 O3while slight increase in weight was noted for Sr0.9 Y0.1 Ti0.8 V0.2 O3. The measured zeta potential suggests that the materials are in the range of moderate stability to resists aggregation from colloidal suspension.
Low Ni-Containing Anodes Using Titanate-Based Perovskites for Methane Direct Internal Reforming Power Generation
Authors: Kikuchi Ryuji , Minori Daisuke , Takagaki Atsushi , Sugawara Takashi , Oyama Shigeo Ted
Published: July 2015

In this study titanate-based perovskite anodes containing Ni such as Ni-LaxSr1-xTiO3 (LST) have been investigated as anodes for direct internal reforming solid oxide fuel cells, which directly utilize hydrocarbons as fuels in the anode. Catalytic activity tests of Ni-titanate cermets were carried out in methane steam reforming, and Ni-LST exhibited comparable activity to Ni-YSZ (yttria-stabilized zirconia). It was found that moderate power generation performance was observed over Ni-LST prepared by the impregnation method when the Ni content was decreased to 10 wt%, whereas almost no current was attained over Ni-YSZ for the decrease in the Ni content. The 10 wt%Ni-LST anode prepared by the impregnation method exhibited stable power generation characteristics in severe direct internal reforming operation at steam-to-carbon ratio of 0.1 at 1000 ºC under a constant current load of 200 mA cm-2.
Screen Printed Porous La0.20Sr0.25Ca0.45TiO3 Fuel Electrode Scaffold Microstructures: Optimisation of Interaction with Impregnated Catalysts for More Durable Performance
Authors: Price Robert , Cassidy Mark , Schuler J. Andreas , Mai Andreas , Irvine John T. S.
Published: July 2015

La0.20Sr0.25Ca0.45TiO3 (LSCTA-) shows promise as a novel Solid Oxide Fuel Cell anode backbone material (to replace Ni-based cermets). Thick film ceramic processing techniques have been used as the primary method in controlling the characteristics of the fuel electrode (layer thickness, porosity, grain connectivity and the ultimate interaction with catalyst particles) in order to produce a microstructural architecture which has the potential to deliver higher electronic (and ionic) conductivity, improved current distribution and more durable performance in fuel cell testing. Results of preliminary studies into the ceramic processing of LSCTA- are presented here.
The Effect of Mn Co-doping on the Electrochemical Properties of Gd0.2Ce0.8O1.9-
d/Pt Model-composite Electrodes
Authors: Velicsanyi Peter , Gerstl Matthias , Nenning Andreas , Hutter Herbert , Fleig Jürgen , Opitz Alexander Karl
Published: July 2015

Model-type thin films of Gd doped and Gd/Mn co-doped ceria were investigated by means of impedance spectroscopy in a humid H2 atmosphere. A novel measurement technique for microelectrodes with interdigitating Pt current collectors was employed. This method allows a separation of the different elementary processes contributing to the electrode impedance. After annealing at 650°C in humid H2 atmosphere, an increase in catalytic activity of Gd/Mn co-doped ceria was observed.
Evaluation of the Influence of Nickel Addition on LST-CGO Based Solid Oxide Fuel Cell Anodes Performance
Authors: Yurkiv Vitaliy , Constantin Guillaume , Gondolini Angela , Mercadelli Elisa , Sanson Alessandra , Dessemond Laurent , Costa Rémi
Published: July 2015

In this paper we present the combine modeling and experimental study of electrochemical hydrogen oxidation at an alternative perovskite based mixed-conducting SOFC anode. Two types of button cells without and with addition of nickel (Ni) were fabricated based on La0.1Sr0.9TiO3-α(LST)-CGO composite anodes and dense YSZ electrolytes. Electrochemical experiments were performed using symmetrical cell configuration in H2/H2O fuel mixture systematically varying applied potentials and operating temperatures. The previously developed model, which includes thermal chemistry at each surface, charge-transfer processes and reactive porous media transport, was employed. It was found that in the case of conventional LST based anodes heterogeneous and charge transfer chemistry at LST surface has capacitive behavior and alters the impedance spectra. However, if nickel is added the influence of LST surface chemistry is diminished leading to an improvement of cell performance.
Gradient Anode Functional Layer for Thin Y:BaZrxCe1-XO3 Electrolyte in Low-Temperature Solid Oxide Fuel Cells
Authors: Bae Kiho , Lee Sewook , Jang Dong Young , Kim Hyun Joong , Lee Hunhyeong , Shin Dongwook , Son Ji-Won , Shim Joon Hyung
Published: July 2015

Microstructure and fuel cell performance of thin film protonic ceramic fuel cell (PCFC) with yttrium doped barium cerate-zirconate (BCZY) are investigated in this work. Thin electrolyte (thickness < 1 μm) is fabricated using pulsed laser deposition on a novel anode functional layer (AFL) which has gradient composition of BCZY and NiO. Electrostatic slurry spray deposition is utilized to fabricate the gradient AFL. In microstructure observation of the PCFC, fully dense thin electrolyte with good interfacial adhesion is confirmed. From fuel cell test, the high maximum power densities of 462‒605 mW/cm2 are obtained at operating temperatures of 550‒650 ºC, along with open circuit voltages of 0.95‒0.87 V.
Fabrication of Bimetallic (NiFe) Anode-Supported SOFCs with Direct Ceramic Inkjet Printing
Authors: Fakeeh A , Tomov R I , Kumar Vasant R , Glowacki B A
Published: July 2015

The bimetallic nickel-iron anode-supported SOFCs were fabricated, with their microstructure analysed, and the performance evaluated at the intermediate temperatures. The produced anode supports were made with the base composition of NiO:Fe2O3 (7:3)mol% and addition of sintering aids. The discs-shaped substrates were die-pressed, with the active layers deposited using Direct Ceramic Inkjet Printing (DCIJP) of suspension inks. The 10µm thicknesses were achieved for the printed electrolyte layer. The DCIJP has also enabled infiltrating the scaffolds of porous supports, thus extending the active area of electrode. The electrolyte material was comprised of 10Sc1CeSZ, whereas cathode was LSCF/CGO composite. Samples with fully co-sintered active layers were produced, alongside the optimised amount of additives, and the adjusted coefficients of thermal expansions. The cell was tested in 4%H2 in Ar gas and dry air, and has displayed open circuit potential of ~0.8V at 750°C.
In-Situ Exsolution of Nano Transition Metal Particles on Lanthanum Chromite Perovskite Anode for Solid Oxide Fuel Cells
Authors: Sun Yi-Fei , Wang Meng-Ni , Luo Jing-Li
Published: July 2015

The physical and electrochemical properties of lanthanum chromite perovskites in which a portion of Cr cations have been substituted with transition metals (La0.6Sr0.3Cr0.85M0.15, M= Ni, Fe, Co) were investigated and the suitability of the materials for use as anode in solid oxide fuel cell (SOFC) was assessed. The SEM results show that the well dispersed nano transition metal particles were successfully prepared by growing them in-situ directly from its perovskite parent backbone under anode reaction condition. And these particles can re-resolve into the lattice when exposed to oxidizing condition. The SOFCs exhibited desirable electrochemical performance in both sweet and sour fuels. It is demonstrated that the promoting effect should be attributed to the decoration of nano transition metals which enhanced the electronic conductivity and catalytic activity.
Mechanistic Considerations of Liquid Metal Anode SOFCs Fueled with Hydrogen
Authors: Toleuova Aliya , Maskell William C. , Yufit Vladimir , Shearing Paul R. , Brett Dan J.
Published: July 2015

Liquid metal anode (LMA) solid oxide fuel cells (SOFCs) are a promising type of high temperature fuel cell suitable for the direct oxidation of gaseous or solid fuels in the bulk of liquid metal. Depending upon the operating conditions, they can be run in four different modes. In the present study, concerning the mechanism of reaction and species transport in LMA SOFCs, the oxidation of fuel (H2) in the bulk of a liquid tin anode has been investigated via operation in so-called Chemical - Electrochemical mode (CE mode) and Electrochemical - Chemical (EC) modes. Theoretical considerations to be applied in the modelling of the obtained experimental data regarding the dissolution of hydrogen in a molten tin anode and its oxidation with oxygen dissolved in liquid tin followed by anodic oxygen injection in mode CE are also discussed.