bluuebunny/crossref_metadata_2025 huggingface dataset:
A Global Framework for Examination of Degradation in SOFC
Authors: Gerdes Kirk , Williams Mark C. , Gemmen Randall , White Briggs
Published: October 2013

In the context of solid oxide fuel cells, degradation can be defined as the departure of any functional SOFC structure from its designed state. Degradation may occur in any active atomic scale structure, grain, phase, interface, component, cell, stack, or system and may occur at the instant of start-up and proceed continuously through tens of thousands of hours of operation. From a fundamental point of view, the degradation of material structure impacts function and performance and can occur as surface phenomena or within the bulk of the material. A global framework of degradation 1) supports the commercialization of SOFC technology; and 2) facilitates commercial adoption of technical innovations developed through fundamental research. A well conceived framework identifies common domains of inquiry in space and time, and supports alignment of fundamental investigations and industrial priorities. In this paper, a global framework for examination of SOFC degradation is proposed. The selection of domains identified within the framework are justified with reference to underlying physical processes of degradation, and to known primary modes of degradation reported in literature. The generalized framework is populated with specific examples, and applied to a series of operating states to demonstrate analytical utility.
Performance of an Anode Supported Solid Oxide Fuel Cell with Indirect Internal Reforming
Authors: Park Sungtae , Zou Jing , Yoon Heechul , Sammes Nigel Mark , Chung Jong Shik
Published: October 2013

The conversion of fuel into hydrogen-rich gas is necessary for fuel cells. This can be achieved either indirectly in fuel processing systems, in which the hydrocarbon feed is converted in an external catalytic steam reformer, or directly in the fuel cell. In this paper, the unit module of solid oxide fuel cell was assembled by one reformer and four cells. The reformer was fabricated by extruded dummy cell and combined with two cells on each side respectively. The reforming catalyst was coated on internal channel of the dummy cell. The unit module has successfully tested with wet CH4 as fuel and air as oxidant and its maximum power density exceeded 150 mW/cm2 at 750 ºC.
Higher Performance, Eco- Friendliness, and Reliability for the “SOFC + μGTE” Hybrid Engine and a Lower Cost of the Power Generated
Authors: Sudarev Anatoly Vladimirovich , Konakov V. G.
Published: October 2013

A mutual positive effect, increasing the economic, environmental and life values of the overall hybrid system is implemented in the hybrid engine based on solid oxide fuel cell (SOFC) and eco-friendly ceramic high-temperature (up to 1350 ° C) gas turbine micro engine (μGTE). Should syngas be used as fuel, the 65-70% efficiency of the hybrid engine can be realized at the emissions of the toxic exhaust components (NOx, CO, CnHm) not higher 5 ppm. Both the introduction of uncooled ceramic membranes into the hybrid engine for separation of hydrogen from the high temperature (up to 11000C) CO-containing stream and using a hydrogen storage on the magnesium hydride and fullerene soot basis increase the efficiency and reliability of the electrochemical reactions of the SOFC, extends application of natural gas, allows carrying out a timely variation of the hybrid engine load.
Cathode Supports of SOFCs with a Hierarchical Pore Structure
Authors: Dong Dehua , Shao Xin , Wang Zhitao , Parkinson Gordon M , Li Chun-Zhu
Published: October 2013

Cathode-supported SOFCs are attractive for the potential utilization of hydrocarbons as fuels to generate electricity because Cu-based anodes can be used to deal with coke formation in the Ni-base anodes. However, Cu-based anodes cannot be used in anode-supported SOFCs because the high sintering temperatures (above 1350 °C) required for the formation of a dense electrolyte film may melt the Cu-based anodes. Compared with anode materials, cathode materials show higher sinterability, which leads to a low porosity of the supporting cathodes and in turn high gas diffusion resistance within the cathodes. To get around this problem, a novel supporting cathode with efficient gas diffusion channels will be developed in this study in order to achieve high performances in power generation.
Application of FIB-TOF-SIMS and FIB-SEM-EDX Methods for the Analysis of Element Mobility in Solid Oxide Fuel Cells
Authors: Kanarbik Rait , Möller Priit , Kivi Indrek , Lust Enn
Published: October 2013

The solid oxide fuel cell single cells with porous Pr0.6Sr0.4CoO3-δ and La0.6Sr0.4CoO3-δ (PSCO, LSCO respectively) cathodes on compact Ce0.9Gd0.1O2-δ|Zr0.85Y0.15O2-δ or Ce0.9Gd0.1O2-δ|Zr0.85Sc0.15O2-δ bi-layered electrolytes deposited onto Ni-Zr0.85Y0.15O2-δ (Ni-ZYO) or Ni- Ce0.9Gd0.1O2-δ (Ni-CGO) supporting anode were prepared for ion (element) mobility studies. Focused ion beam - time of flight - secondary ion mass spectrometry (FIB-TOF-SIMS) method in addition to FIB-SEM, SEM-EDX and XRD methods has been used for analysis of mass-transfer (interlayer diffusion) of cathode electrode elements, demonstrating that during PSCO and LSCO sintering at 1100°C on to CGO|ZYO or CGO|ZScO bilayered electrolyte, noticeable mass-transfer of Sr2+ cations through the partially microporous CGO has been verified using FIB-TOF-SIMS and SEM-EDX methods. The single cells have been additionally studied using cyclic voltammetry, electrochemical impedance and chronoamperometry methods and high power densities have been demonstrated.
Cubic-Tetragonal Phase Transformation of YSZ Electrolyte in SOFCs
Authors: Shimonosono Taro , Kishimoto Haruo , Nishi Mina , Brito Manuel E. , Yamaji Katsuhiko , Yokokawa Harumi , Horita Teruhisa
Published: October 2013

In view of long term reliability of SOFCs, the prediction of voltage degradation is essential. In yttria-stabilized zirconia (YSZ) generally adopted as electrolyte, the degradation of electrical conductivity is known to be caused by the phase transformation of the cubic to the tetragonal phase over the long term of several thousand hours. Using model YSZ electrolyte under SOFC operating condition, we have so far examined the parameters dominating the behavior of phase transformation. We clarified that the acceleration of phase transformation was caused by the dissolution of NiO into YSZ electrolyte and the following formation of low oxygen potential in YSZ electrolyte, and that the acceleration was significantly suppressed with decreasing temperature. Based on such effects on the phase transformation, we tried to predict the conductivity degradation due to phase transformation of electrolyte during long term operation.
Chemical Expansion in SOFC Materials: Ramifications, Origins, and Mitigation
Authors: Bishop Sean R. , Marrocchelli Dario , Perry Nicola H. , Tuller Harry L. , Watson Graeme , Yildiz Bilge , Amezawa Koji , Kilner John A.
Published: October 2013

Non-stoichiometric oxides are frequently used in SOFC electrodes due to the ease with which they exchange oxygen with the atmosphere over their entire surface, as compared to composites limited to three phase boundaries (i.e. LSM/YSZ). The large fluctuations in oxygen content these materials exhibit during operation lead, not only to significant changes in transport properties, but also to a defect induced expansion, known as chemical expansion, potentially contributing to mechanical failure. In this presentation, new insights into the origins of chemical expansion, with consequent development of methods for reducing its impact in non-stoichiometric oxides, facilitated by collaborations of the authors, will be discussed.
Performance Evaluations for Long Term Durability and Reliability of Segment-In-Series Tubular Type SOFCs
Authors: Yamamoto Tohru , Yasumoto Kenji , Yoshikawa Masahiro , Morita Hiroshi , Mugikura Yoshihiro
Published: October 2013

Long term durability and reliability tests of five different types of SOFCs and stacks, which have been developed by Kyocera, MHI, MMC/KEPCO, Tokyo-gas and TOTO, were carried out under the NEDO project (FY2008–2012). In this paper, we report the result of durability tests of segment-in series tubular type SOFC stacks fabricated by MHI. The voltage loss factors such as internal resistance and polarizations of anode and cathode were also determined by the electrode performance model. The cathode polarization of improved segment-in series tubular type SOFC stack was greatly reduced and the durability of stack was also improved by the application of cathode side SDC/YSZ interlayer. In the long term durability test, improved stacks exhibited no degradation for 10,000 hours without chromium exposure and also strong tolerance against chromium contamination in cathode air for 15,000 hours (degradation rate of output voltage: 0.16%/1,000 hours).
Reliability of an All Perovskite-Based Solid Oxide Fuel Cell
Authors: Lo Faro Massimiliano , Aricò Antonino S.
Published: October 2013

A solid oxide fuel cell (SOFC) has been manufactured using a Ni-modified perovskite and perovskite-based electrolyte and cathode. The SOFC has been investigated for operation at intermediate temperatures. In this regard, we have first studied the electrical properties of La0.8Sr0.2Ga0.8Mg0.2O3 (LSGM) and gadolinia-doped ceria (GDC) electrolytes and afterwards we have investigated the reliability of the Ni-modified La0.6Sr0.4Fe0.8Co0.2O3 based anode operation in combination with LSGM electrolyte and La0.6Sr0.4Fe0.8Co0.2O3 (LSFC) cathode. A 50 h electrochemical test for the SOFC operation under different fuel feed is presented to show the reliability characteristics of such SOFC architecture.
Development of a High-Performance Micro-Tubular SOFC Based on a Hollow Fiber Support
Authors: Panthi Dhruba , Tsutsumi Atsushi
Published: October 2013

A new design of micro-tubular solid oxide fuel cell (SOFC) is proposed to improve current collection efficiency from the bore side. The proposed micro-tubular SOFC uses a ceramic hollow fiber as a support component above which functional layers are deposited. The provision of a thin porous layer of a current collector above the cell support makes it possible to collect current from the entire surface of the inner electrode. The thermal-fluid and electrochemical phenomena in the proposed design are studied through computational fluid dynamics (CFD) simulations. The simulation results suggest that due to significantly reduced ohmic losses, the proposed design is able to deliver a superior performance compared to the conventional anode-supported micro-tubular design. Finally, for the realization of the proposed design, the preparation of yttria-stabilized zirconia (YSZ) hollow fibers through an electrophoretic deposition (EPD) method is also discussed.
Design and Fabrication of Micro SOFC for the Power Source of Mobile Electric Devices
Authors: Murayama S. , Iguchi Fumitada , Inagaki Y. , Shimizu Makoto , Tanaka S. , Yugami Hiroo
Published: October 2013

A package for the power source of mobile electronic devices based on micro solid oxide fuel cells (micro-SOFCs) was designed considering thermal management. The package should suppress its surface temperature lower than harmless value for other electrical circuits, and thermal consistency should be kept. In addition, other functions such as gas flow and electrical connection were installed into the package. Hence, high performance thermal insulation structure with good machinability was necessary. We applied thermal insulation structure made of Si wafers and glasses by MEMS technologies. The convection heat transfer was prevented by the structure equipped with a vacuum zone. Experimental and theoretical consideration revealed that the purpose could be achieved at apparent thermal conductivity of the structure lower than 0.02 W/ mK. In accordance with the consideration, a package was designed, and its thermal insulation performances were evaluated.
Technological Issues in the Manufacturing of Anode-Supported Half-Cells
Authors: Mercadelli Elisa , Pinasco Paola , Gondolini Angela , Sanson Alessandra
Published: October 2013

The production of planar, anode-supported half-cell with suitable morphological characteristics needs a careful control of the thermal treatments involved. Although the thermal profiles are generally well analyzed in literature, the role played by the setter plates on the half-cell manufacturing is generally neglected although they can strongly affect the final results. In this study the influence of the nature of setter plates in the production of large area NiO-YSZ/YSZ half cells was deeply investigated. In particular the performance and the possible interaction of the SiC, alumina and zirconia setter plates with the half-cell during the sintering stage were thoroughly evaluated in order to assess the best thermal set-up.
Processing Effects on Performance and Stability of Anode-Supported Fuel-Cells
Authors: Li Wenxia , Palanisamy Ponnusamy , Webb Richard , Minh Nguyen Q
Published: October 2013

Optimized performance of a fuel cell membrane electrode assembly (MEA) depends on several factors. Key among them are the electrolyte density and the interface between the electrolyte and electrodes (anode and cathode). In this work, SOFC half cells were fabricated by tape casting, lamination, and co-sintering with constraint. These half-cells were then printed with cathode material and re-fired to form the MEA. The effect of both constraint and firing profile were investigated. Optimization of firing profile and constraint load facilitated production of MEA’s with minimal camber. Study of these cells, fired in different profiles, displayed that interface issues easily overshadow the effect of electrolyte density with regard to cell performance and stability in use. In addition, infiltration was performed on the as-fabricated single cell samples. The performance of the infiltrated cell conducted in 100% hydrogen as well as in 7.3% ethanol in helium will be presented.
Towards a Fully REDOX Stable SOFC: Cell Development at Ceres Power
Authors: Leah Robert , Lankin Mike , Bone Adam , Selcuk Ahmet , Pierce Robin , Rees Lee , Corcoran Derek , Muhl Patrick , Dehaney-Steven Zac , Brackenbury Colin , Mukerjee Subhasish
Published: October 2013

Low-temperature SOFCs with thick-film anodes such as those developed by Ceres Power for its metal supported SOFC are inherently more resistant to REDOX cycling as a result of loss of fuel supply at temperature than traditional SOFC designs. This is due to the slow kinetics of nickel oxidation at low temperature and the anode not being the main structural support for the cell layers. High REDOX stability is essential for widespread commercial adoption of SOFC technology as the requirement to supply a protective atmosphere over the anode during uncontrolled shutdowns otherwise adds substantial cost and complexity to the system. The latest generation of Ceres Power metal supported cells show exceptional resistance to REDOX and thermal cycling, even in very aggressive accelerated tests. This has been achieved through development of the anode to achieve very robust microstructures at low processing temperatures. This paper will illustrate the current anode microstructure and the latest accelerated testing results.
Novel Strategies to Fabricate an Anode Supported-Type Protonic Ceramic Fuel Cells (PCFCs)
Authors: Lee Jong-Ho , Choi Sung-Min , Park Su-Byung , Yoon Kyung Joong , Son Ji-Won , Je Hae-June , Kim Byung-Kook , Lee Hae-Weon
Published: October 2013

Protonic ceramic fuel cells (PCFCs) based on BaZr1-xYxO3-δ (BZY) have attracted great attention as an alternative for the conventional high temperature fuel cells based on oxygen conducting electrolyte. However, this BZY-based PCFC technology still has many technical problems, especially related with the poor sinterability of BZY electrolytes. In order to overcome this poor sinterability which is a critical limitation in making a thin and dense electrolyte layer for anode-supported PCFCs, we employe the sintering aid-assisted enhanced sintering of BaZr0.85Y0.15O3-δ (BZY). We also promote the densification of BZY layer by utilizing the higher sinterability of BaCe0.9Y0.1O3-δ (BCY) that is attached to the top of BZY layer. From proper adjusting of the shrinkage behaviors of both anode substrate and dual electrolyte layer, we could fabricate fairly dense BZY/BCY electrolyte layer with less than 10 micro-meter thickness.
Hydrogen Membrane Fuel Cells with Metal/Insulator/Metal Structure
Authors: Aoki Yoshitaka , Nonaka Ryo , Habazaki Hiroki
Published: October 2013

Novel thin film fuel cell based on the 100 nm-thick electrolyte of amorphous ZrP2.5O
x
, working at 400°C, was demonstrated. The hydrogen permeable membrane fuel cell (HMFC) using a Pd foil　as a nonporous solid anode was fabricated. Ni interlayer of several hundreds nm thickness was introduced between the Pd anode and the ZrP2.5O
x
electrolyte in order to suppress the deterioration of the electrolyte nanofilm by the deformation of the Pd anode during hydrogen absorption. In the ZrP2.5O
x
electrolyte the transport number of proton was unity at 400°C as determined by an EMF measurement. The modification of the Ni anode surface by an ultrathin Pt or Pd layer effectively decreased the anode/electrolyte interfacial polarization. Consequently, the HMFC revealed the OCV of 1.0 V and the maximum power density of 3.6 mW cm-2 at 400°C.
Investigation of Microstructure of Sr-Doped Lanthanum Vanadium Oxide Anode Based on SDC Electrolyte
Authors: Tamm Kadi , Raudsepp Ragle , Kanarbik Rait , Möller Priit , Nurk Gunnar , Lust Enn
Published: October 2013

Three different single solid oxide fuel cells based on Ce0.85Sm0.15O2-δ electrolyte were prepared by infiltration method varying the microstructure of the porous Ce0.85Sm0.15O2-δ scaffold. La0.8Sr0.2CoO3-δ was used as the cathode and La0.3Sr0.7VO3-δ as the anode activated with CeO2 and Pd nanoparticles. The microstructure of the porous Ce0.85Sm0.15O2-δ scaffolds was characterized using modified FIB-SEM. Single cell with the finest electrolyte framework and the highest porosity of the scaffold exhibited the best power density value, 320 mW cm-2 at 873 K, using humidified hydrogen as the fuel. In contrast, the single cell with somewhat lower porosity of the scaffold and bigger Ce0.85Sm0.15O2-δ particles, but with similar pore sizes, had the best power density value, 175 mW cm-2 at 873 K, using humidified methane as the fuel.
Capabilities and Challenges for Tungsten Carbide Anodes
Authors: Torabi Alireza , Etsell Thomas H.
Published: October 2013

This work is focused on development of tungsten carbide-based materials as alternative anodes for SOFCs operated on methane or hydrogen-methane mixtures. Not only are the capabilities of the anodes highlighted, but the challenges are also stressed. While WC-YSZ anodes were resistant to carbon formation under CH4, the fuel was poorly activated. Additionally, catastrophic changes in the microstructure were observed. The addition of CeO2 and Ru promoters, however, was found to significantly boost the performance and to improve the stability of WC. Finally, this study indicates that Ni modified WC-based anodes are compatible with methane fuel, giving reasonable and stable performance.
Beneficial Effects of Low ppm Levels of H2S on the Performance of Ni-YSZ SOFC Anodes in Syngas Fuels
Authors: Singh Anand , Paulson Scott , Hill Josephine M. , Birss Viola
Published: October 2013

Carbon accumulation (coking) normally occurs at the Ni-yttria stabilized zirconia (YSZ) cermet anode of solid oxide fuel cells (SOFCs) when they are operated on carbon-containing fuels, such as syngas (H2 + CO). Here we show that the addition of ppm levels (4-17 ppm) of H2S to a syngas stream, at 600 oC and even at low current densities (5-15 mA/cm2), prevents anode coking and stabilizes the anode performance, as demonstrated for the first time using 3-electrode methods. It is also shown that the onset of coking (in the absence of H2S) causes an initial improvement in anode performance, although this is only a transient phenomenon, eventually resulting in a highly degraded Ni-YSZ anode structure. Even so, this initially enhanced performance could potentially be used as an indicator of the onset of coking, thus allowing the modification of stack operating conditions to prolong their lifetime.
Advanced Electrodes for Intermediate Temperature Proton Conducting Fuel Cell
Authors: Taillades Gilles , Pers Paul , Batocchi Pierre , Taillades Melanie
Published: October 2013

In order to develop efficient Protonic Ceramic Fuel Cell, different composite electrodes made of BaCe0.9Y0.1O3 and NiO or mixed ionic-electronic conductor (BSCF) were investigated as anode and cathode respectively. Ni-BCY composite synthesized by combustion offers sufficient open porosity, shows an electrical conductivity superior to 1000 S.cm-1 and a very low ASR value (0.06 Ω.cm2
at 600°C). The electrochemical properties of BSCF-BCY composite cathode have been studied and the obtained ASR value (0.53 Ω.cm2 at 600 °C) is lower compare to pure BSCF. An anode supported single cell (25 mm in diameter) consisting of a bi-layer Ni-BCY cermet, a dense 15 mm BCY electrolyte and a BCY-BSCF composite cathode were assembled and tested from 550 to 700 °C. Open circuit voltages of 1.055 V and 1.026 V were achieved at 600 °C and 700 °C. Maximum power densities of 156 and 293 mW.cm-2 were obtained at 600 and 700 °C.
Microstructural Engineering of SOFC and SOEC Electrode Interfaces
Authors: Irvine John T. S.
Published: October 2013

The most important electrochemical reactions in a solid oxide fuel cell or electrolyser take place within a few microns of the electrolyte interface Here we compare and contrast two new ways to design and control this interface. The first is impregnation of precursor solutions to form nanoscale electrocatalysts in situ and the second is exolution of buried catalysts as nano-scale particles. The evolution of nanostructure under operating conditions is described and promising electrochemical performance data presented in both SOFC and SOEC modes.
Evaluation of Electrolyte Breakdown Condition in an Anode-Supported SOFC Due to Ni-Zirconia Cermet Anode Reoxidation
Authors: Tahara Yuri , Orui Himeko , Watanabe Kimitaka , Sugita Satoshi , Kobayashi Ryuichi
Published: October 2013

An emergency shutdown of an SOFC system gives rise to an increase of the anode-side partial pressure of oxygen (p(O2),a). This leads to electrolyte breakdown due to the anode strain caused by Ni-zirconia cermet reoxidation. We determined the open circuit voltage recovery and drop conditions at various (p(O2),a)’s and temperatures and clarified the electrolyte breakdown conditions in an anode-supported cell. In addition, we investigated the anode strain under the neighborhood of electrolyte breakdown conditions by dilatometry. The results indicate that the electrolyte was broken when anode strain is over 0.25%.
A Novel Concept for In Situ Gas-Phase Laser Raman Spectroscopy for SOFC
Authors: Schiller Guenter , Auer Corinna , Ilhan Zeynep , Szabo Patric , Ax Holger , Kapadia Bhavin , Meier Wolfgang
Published: October 2013

Gas-phase laser Raman spectroscopy has recently been adopted to determine the concentrations of relevant gaseous species within the anode flow channel with high spatial and temporal resolution during operation at technically relevant operating conditions. The paper describes the configuration of an optically accessible SOFC, the laser system and optical setup for 1 D Raman spectroscopy as well as the challenges associated with the measurements of an electrolyte supported cell of a size of 50 x 50 mm2. At different operating conditions Raman spectra were recorded and concentration profiles of gas species along the flow path in the anode were determined demonstrating this new experimental approach for a better understanding of SOFC processes.
Characterization of a Novel Ni-Impregnated GDC Electrode for Solid Oxide Fuel Cell and Electrolysis Cell Applications
Authors: Lomberg Marina , Ruiz-Trejo Enrique , Offer Greg , Kilner John A. , Brandon Nigel P.
Published: October 2013

In this study a novel electrode structure for both fuel cell and electrolysis was made by impregnation of a porous Gd-doped Ceria scaffold with Ni nano-particles. Electrical conductivity was assessed by the Van der Pauw method. Electrochemical performance in dry hydrogen was evaluated using three electrode DC and AC measurements over a range of temperatures and gas concentrations. The microstructure of the electrode was studied using Scanning Electron Microscopy. Encouraging results have been obtained for the performance of the electrode and results from these studies are reported.
Identification of Ni-YSZ Anode Creep Property Using PSO for Multiscale Simulation
Authors: Watanabe Satoshi , Iguchi Fumitada , Sato Kazuhisa , Yamamoto Koji , Hashida Toshiyuki , Terada Kenjiro , Kawada Tatsuya
Published: October 2013

Our group has attempted to construct an SOFC multiscale model which can simulate inelastic deformation under operating conditions. In this study, we have focused on mechanical properties of Ni-YSZ anode and aimed to identify creep parameter which is a key factor of inelastic deformation. Measurements were performed at elevated temperatures under controlled oxygen partial pressures using in-situ mechanical testing equipment. Creep parameters of Ni-YSZ anode was optimized to have least difference between the result of numerical material test and experiment, using Particle Swarm Optimization (PSO) algorithm of the approximate optimization techniques based on behavior of self-organized system. As a result, we could confirm transit creep on Ni-YSZ cermet, and identify parameters of it. Simulated creep curves showed good fitting to experimental curves at applied stress up to 5MPa but, deviated at higher applied stress.
Performance of LSTN(La0.2Sr0.8Ti1-xNixO3-δ) Alternative Anode for SOFC in H2 and CH4
Authors: Park Byung Hyun , Choi Gyeong Man
Published: October 2013

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 can be produced using exsolution method or produced in oxide anodes after exposure to reducing atmosphere. In this study, we have used LSTN (La0.2Sr0.8Ti1-xNixO3-ä) as an alternative anode and investigated its electrochemical performance. Impedance spectra and power measurement of the cell with the exsolution anodes have shown the improved performance of LSTN anode in hydrogen and methane fuel.
Exchange Current Density of SOFC Anodes
Authors: Hosoi Takami , Yonekura Takahiro , Sasaki Kazunari
Published: October 2013

While Solid Oxide Fuel Cells (SOFCs) have attracted increasing attention, there are only a limited number of papers on exchange current density, representing electrode activity to describe and simulate SOFC performance. In this study, theoretical relationships on anode exchange current density has been derived as a function of various operational parameters by taking into account elementary reaction processes. Analytical relations under various boundary conditions are also derived with respect to gas partial pressures.
Optimization of Infiltration Techniques Used to Construct Ni/YSZ Anodes
Authors: Keyvanfar Parastoo , Birss Viola
Published: October 2013

A range of Ni-containing solutions have been infiltrated into a symmetrical tubular half-cell composed of a slip-casted, porous yttria-stabilized zirconia (YSZ) anode support, Ni-YSZ functional layers, a YSZ electrolyte, and a second, outer porous YSZ anode support layer, aiming at the development of high performance anodes that are tolerant to redox-cycling. A combination of surface wettability experiments and optical and electron microscopy imaging has been used to determine how well these solutions penetrate the porous YSZ matrix, then correlating these results with the electrochemical performance in humidified H2 environments at 800 ⁰C. It is shown that the addition of the Triton-X-100 surfactant to the infiltration solution results in excellent penetration of the YSZ matrix, while the use of urea as a Ni complexing agent does not give good wettability, thus leaving a Ni-rich layer on the outer anode surface. Overall, the use of a two-step process, involving several infiltrations with Ni nitrate solutions containing Triton-X-100, followed by several infiltrations with urea-containing solutions, leads to the best cell performance as well as the best Ni distribution inside the anode layers.
Oxygen Non-Stoichiometry, Defect Equilibrium and Electrical Properties of La0.8Sr0.2Sc0.2Mn0.8O3±δ
Authors: Sengodan Sivaprakash , Kim Junyoung , Shin Jeeyoung , Kim Guntae
Published: October 2013

Non-stoichiometric variation of oxygen content in La0.8Sr0.2Sc0.2Mn0.8O3±δ
were determined by means of coulometric titration as a function of oxygen partial pressure p(O2) and temperature. La0.8Sr0.2Sc0.2Mn0.8O3±δ
oxides shows oxygen excess and oxygen deficient composition depending on p(O2). Random defect model was constructed based on the experimental oxygen non-stoichiometry. The non-stoichiometric variation of oxygen content of La0.8Sr0.2Sc0.2Mn0.8O3±δ
can be explained by the defect equilibrium model. Thermodynamic quantities such as partial molar enthalpy and partial molar entropy were calculated using Gibbs-Hemholtz equation. Electrical conductivity measurements were performed as a function of oxygen partial pressure and temperature, which shows a typical p-type behavior.
(La,Ba)CoO3 and Pr1.9(Ni,Cu,Ga)O4 Composite Oxide as Active Cathode for Intermediate Temperature Solid Oxide Fuel Cells Using Doped LaGaO3 Electrolyte Films
Authors: Hong Jong-Eun , Xie Jing , Ida Shintaro , Ishihara Tatsumi
Published: October 2013

Ba0.5La0.5CoO3 (BLC) and Pr1.9(Ni,Cu,Ga)O4 (PNCG) composite cathode were investigated to enhance electrochemical performance in solid oxide fuel cells using Sr- and Mg-doped lanthanum gallate (LSGM) electrolyte films at intermediate temperatures (773–973 K). Effect of the calcination temperature of the composite cathode was studied on chemical compatibility, area specific resistance (ASR), and power generation property. ASR of the composite cathode was smaller than that of SSC but increased with increasing calcination temperature by chemical reaction. Improved maximum power density of 1.270 and 0.146 Wcm-2 at 973 K and 773 K was achieved on a single cell using BLC-PNCG composite as cathode on LSGM film.
Changes In LSC and LSCF Cathode Crystallographic Parameters Measured by Electrochemical In Situ High-Temperature XRD
Authors: Kivi Indrek , Aruväli Jaan , Kirsimäe Kalle , Heinsaar Alar , Nurk Gunnar , Lust Enn
Published: October 2013

The solid oxide fuel cell symmetrical cells with porous cathodes for intermediate temperature applications have been studied under electrochemical polarization and oxygen feeding conditions using high-temperature in situ XRD (HT-XRD) method. Changes in the lattice parameters of La0.6Sr0.4CoO3
−δ and La0.6Sr0.4Co0.2Fe0.8O3
−δ were observed depending on the temperature (T), electrode potential (E) and oxygen partial pressure (p
O2) applied. At fixed T and p
O2, the cathode potential noticeably influences the crystallographic cell volume calculated, thus, i.e., the oxygen stoichiometry, explained by the partial reduction of electrochemically labile Co-ionic centers in La0.6Sr0.4CoO3
−δ (LSC) and the La0.6Sr0.4Co0.2Fe0.8O3
−δ (LSCF) under study. Noticeably higher effect of cathode potential on the cell volume has been established at lower p
O2.
Microscopic Observation on Deposited Chromium Near the Cathode Reaction Site of SOFCs and Influence of Cathode Polarization Change
Authors: Park Eunjoo , Taniguchi Shunsuke , Daio Takeshi , Chou Jyh-Tyng , Sasaki Kazunari
Published: October 2013

We already clarified that chromium deposition near the cathode/electrolyte interface was predominantly affected by the cathode polarization and the chromium deposition occurred not only on the cathode materials (LSM, LSCF etc.) but also on the electrolyte material, which seems to be involved in the electrode reaction sites. In this study, influence of cathode polarization change on the distribution of the deposited chromium was investigated by using LSM cathode. Microstructure at the cathode/electrolyte interface seems to change by cathode polarization and the microscopic distribution of the deposited chromium can be affected by the change in the microstructure.
Preparation of Cathode Material for Co-Sintering with Electrolyte at High Temperature
Authors: Kon Toshiki , Kamegawa Atunori , Takamura Hitoshi
Published: October 2013

Ti-doped La-Sr-Co-Fe-based oxides (LSTCFs) were prepared as cathode material for co-sintering with electrolyte at high temperatures. LSTCFs have relatively high solid solubility limits of Ti up to 80mol%. Before reaching the solubility limits, LSTCFs were well densified and single phase with a rhombohedral structure (R-3c). Meanwhile, after exceeding the solubility limits, a Ti-rich secondary phase appeared and microstructures tend to be porous. Electrical conductivity and thermal expansion coefficient (TEC) for LSTCF decreased with increasing Ti content. Ti4+appears to work as a donor and suppress electronic spin state transition of Co3+ ions and formation of oxygen vacancies. The composition, such as La0.6Sr0.4Ti0.4(Co0.2Fe0.8)0.6O3-δ (LSTCF28) with 40 mol%Ti and La0.6Sr0.4Ti0.6(Co0.8Fe0.2)0.4O3-δ (LSTCF82) with 60 mol%Ti, showed low sinterability and sufficient thermomechanical compatibility with GDC electrolyte. Those, however, possess more than two order of magnitude lower electrical conductivity than those of typical cathode materials.
Stability of Composite Cathode Consisting of Doped Bismuth Oxide (Y0.25Bi0.75O1.5) and Conducting Perovskite La1-XSrxMeO3-
δ (Me=Mn, Cu)
Authors: Fung Kuan-Zong , Tsai Shu-Yi , Chang Yun-Jie , Jung WooChul , Haile Sossina M.
Published: October 2013

The mixed conducting cathodes for solid oxide fuel cells usually consist of a mixture of oxygen ion conductor and a conducting perovskite oxide. Bismuth oxide based materials are known to exhibit high ionic conductivity. Among them, Y0.25Bi0.75O1.5 (25YSB) is a typical example. On the other hand, La0.8Sr0.2MnO3-δ (20LSM) and La0.75Sr0.25CuO3-δ (25LSCu) are well known cathodes for SOFC applications. In this study, the phase stability of composite cathode consisting of 25LSCu or 20LSM and 25YSB mixed powders was examined. No additional phase other than LSM and YSB was observed at temperatures as high as 1000oC for 8h. However, 25LSCu tends to react with 25YSB and additional phases belonging to La0.3Bi0.7O1.5, La2CuO4, CuO and Bi2Sr2CuO6 appeared after heat treatment at 800oC for 20h. The conductivity of 20LSM-25YSB composite electrode increases with increasing volume fraction of 20LSM. The thermal expansion of 20LSM-25YSB composite electrode was also measured as a function of 25YSB content. Based on these results, 20LSM+25YSB is believed to be the desired composite cathode for SOFC application.
Electrochemical Investigation of Composite Nano La0.6Sr0.4Co0.2Fe0.8O3-δ Infiltration into LSGM Scaffold Cathode on LSGM Electrolyte
Authors: Yoon Byoung Young , Bae Joongmyeon
Published: October 2013

As a potential intermediate temperature SOFC cathode, a nano La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) infiltrated into a porous La0.
8Sr0.
2Ga0.
8Mg0.
2O3-δ (LSGM) scaffold cathode was evaluated in combination with a LSGM electrolyte. A XRD analysis revealed resistive phases of LaSrGa3O7 and LaSrGaO4 present in the LSCF/LSGM binary system with sintering over 950 oC. To fabricate a nano catalyst infiltrated into the LSGM scaffold cathode, the porous LSGM scaffold is formed at high temperature (1250 oC). Nano catalysts are coated on the scaffold surface using an infiltration technique and fired at 850oC in air. The cathode polarization resistance (Rp) of nano LSCF infiltrated into the LSGM scaffold cathode was 0.02 Ωcm2, 0.11 Ωcm2, and 0.66 Ωcm2 at 800oC, 700oC, and 600oC, respectively. To improve the oxygen reduction reaction, a Pt/LSCM composite solution was infiltrated into the LSGM scaffold cathode. However, the Rp of the nano Pt/LSCM composite infiltrated into the LSGM scaffold cathode was increased to 0.90 Ωcm2 at 700 oC, despite the Pt has higher electrochemical activity for oxygen reduction than LSCF (Rp for LSCM infiltration was 0.317 Ωcm2 at 700oC).
Compensation for Oxygen Exchange Rate Limiting Impurities on a Pr0.1Ce0.9O2-
d SOFC Electrode Material
Authors: Bishop Sean R. , Druce John , Kilner John A. , Ishihara Tatsumi , Sasaki Kazunari
Published: October 2013

Impurities on the surface of SOFC electrodes can dramatically reduce their interfacial transport. In this work, we use a novel in situ optical absorption relaxation technique to derive the oxygen exchange rate in the absence of electrodes, thereby studying the “innate” material. Si is found to be an impurity in high concentration, with its presence associated with an orders of magnitude decrease in oxygen exchange rate. Addition of La to the electrode surface is found to substantially improve oxygen exchange rate.
Synthesis and Characterization of La0.6Sr0.4Co0.2Fe0.8O3 Nanofiber/Ce0.9Gd0.1O2 Nanoparticle Composite as Cathode Material for Intermediate Temperature Solid Oxide Fuel Cells
Authors: Gao Chenlong , Liu Yingjun , Kumar R. Vasant
Published: October 2013

La0.6Sr0.4Co0.2Fe0.8O3 (LSCF6428) was synthesized as nanoﬁbers by electrospinning method followed by a simple thermal treatment. The morphology and structure of as obtained nanofibers were characterized by ﬁeld-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). The typical ceramic ﬁber diameter is 100-200 nm, The results showed these materials had a single perovskite phase. Then two forms of LSCF6428: nanofiber and nanoparticles were blended with Ce0.9Gd0.1O2 (CGO91) nanoparticles to fabricate composite cathode. The electrochemical properties of the two composite cathodes were determined using electrochemical impedance spectroscopy (EIS) analysis. The area speciﬁc resistance (ASR), and activation energy of the two composite cathodes were compared at temperatures from 500 to 650ºC, which suggested the LSCF6428 nanofibers has better performance for IT-SOFC than does the nanoparticles.
Performance of Nickel, Platinum, and Lanthanum Strontium Cobaltite as Electrodes for Intermediate-Temperature Solid Oxide Fuel Cells
Authors: Jung Hojean , Jang Dong Young , Bae Kiho , Shim Joon Hyung
Published: October 2013

Performances of Ni, Pt, and lanthanum strontium cobaltite (LSC) were compared as electrodes for solid oxide fuel cells (SOFCs) at temperatures of 350~450°C. Metal electrodes were prepared as a 150nm-thick porous layer by sputtering and LSC was deposited by pulsed laser deposition. It was identified that the Pt cathode was more effective at low temperatures while LSC outperforms Pt over 450°C. SOFCs with the Ni anode performed poor compared to Pt over all temperature regimes tested in this work.
Influence of LSC Cathode Microstructure on the Electrochemical Behavior at the Intermediate Temperature SOFC
Authors: Möller Priit , Kanarbik Rait , Kivi Indrek , Nurk Gunnar , Lust Enn
Published: October 2013

The complex relationship between the microstructure of the mixed ionic-electronic conductor La0.6Sr0.4CoO3-
δ (LSC) and the electrode performance has been investigated on a quantitative level. Symmetric half-cells and single cells with various LSC microstructures were formed using series of raw cathode powders with different particle size distributions. Dual beam FIB-SEM method was used to perform 3-D analysis of microstructure to obtain useful quantitative data such as surface area, volume fractions, pore size distribution, TPB length and tortuosity factor. The results were compared with AC impedance spectroscopy, cyclic voltammetry and chronoamperometry measurements data. It was found that in symmetrical half-cell configuration LSC microstructure, especially the surface area, influences drastically the electrode polarization resistance. The power density was also noticeably affected by the cathode microstructure of the anode supported single cells.
Defect Equilibria Of (Pr0.6Sr0.4)(Co0.2Fe0.8)O3-δ
Authors: Barclay Calvert Sebasdan , Zhao Liang , Bishop Sean R. , Duncan Keith L.
Published: October 2013

The nonstoichiometry of single phase perovskite Pr0.6Sr0.4Co0.2Fe0.8O3-δ (PSCF) was measured in the temperature range 800 ⁰C-600 ⁰C. The nonstoichiometry for PSCF was found to be greater than LSCF for all measured temperatures and oxygen partial pressures (Po2) tested. A defect equilibria model was developed based on small polaron formation on both A-and B-sites of the perovskite Good fits of the model to the experimental data were obtained enabling the relative concentrations of the point defect species in PSCF to be determined.
Factors that Influence Cation Segregation at the Surfaces of Perovskite Oxides
Authors: Lee Wonyoung , Yildiz Bilge
Published: October 2013

As the oxygen reduction reaction (ORR) becomes more critical for development of solid oxide fuel cells (SOFCs) that operate at 500-700 °C, the correlation between the surface chemistry and electrochemical performance is important to understand and enable design of cathode materials with optimal surface chemistry. Recently we demonstrated that elastic and electrostatic interactions of the dopant with the host lattice drive dopant segregation, a detrimental process on the surface of perovskite cathodes [1]. Motivated by those results, here we investigated the effects of A-site stoichiometry in La0.8Sr0.2MnO3 (LSM) thin films on the surface chemistry and electrochemical activity. Angle-resolved X-ray photoelectron spectroscopy was employed to identify the surface cation content and chemical bonding states. A-site deficient LSM films showed higher chemical stability against Sr segregation and secondary phase formation upon annealing. This was correlated with a higher electrochemical activity measured by AC impedance spectroscopy. Given the insulating nature of secondary phases created on the surface upon annealing, observed higher electrochemical stability in A-site deficient LSM films can be ascribed to the suppressed surface segregation and phase separation.
Enhanced Oxygen Reduction Reaction Kinetics In Nanocrystalline IT-SOFC Cathodes
Authors: Baqué Laura Cecilia , Soldati Analía , Troiani Horacio , Schreiber Anja , Caneiro Alberto , Serquis Adriana
Published: October 2013

Solid oxide fuel cell performance is usually limited by high cathodic area specific resistance (ASR) at intermediate temperatures (500-700°C). ASR can be decreased by reducing particle size to nanometer range. This improvement is usually ascribed to the area/volume ratio increase and a higher concentration of active sites for the oxygen reduction reaction (ORR). Nevertheless, this solely explanation seems not to be enough for explaining the high electrochemical performance of some nanostructured La0.4Sr0.6Co0.8Fe0.2O3-d cathodes previously reported (Baqué et al., Electrochemistry Comm. 10 (2008) 1905-1908). Accordingly, the ORR of these cathodes was studied by electrochemical impedance spectroscopy (EIS) under air and under pure oxygen within the 400-700°C range. The nanostructure was characterized even at atomic level by transmission electron microscopy (TEM), revealing that the cathode is composed of nanocrystals surrounded by zones with some degree of crystalline disorder. These results suggest that this kind of nanostructure facilitate the ORR in this compound.
Effect of Coatings on a Commercial Stainless Steel for SOEC Interconnect Application in Anode Atmosphere
Authors: Ardigo Maria Rosa , Popa Iona , Chevalier Sébastien , Parry Valérie , Galerie Alain , Girardon Pauline , Perry Frédéric , Laucournet Richard , Brevet Aude
Published: October 2013

The high temperature steam electrolysis (HTE) represents one of the most promising technologies for mass hydrogen production. A commercial K41X steel (AISI441) containing 18 wt. % of chromium was tested as interconnect for solid oxide electrolyser cells (SOEC). In a previous paper, it was shown that the uncoated alloy is not suitable for SOEC interconnect application at 800°C in O2-H2O atmosphere. It was also proved that the application of a LaNi0.6Fe0.4O3-δ coating on the surface by physical vapour deposition process improves the alloy electrical behaviour and reduces chromium species evaporation. For this study, the same coating was deposited on the alloy surface by screen-printing process. Moreover, two spinel-type oxides, Co2MnO4 and Co3O4, deposited by physical vapour deposition process, were also tested in O2-H2O atmosphere at 800°C. The electrical conductivity did not present any improvement, but the Cr species volatility was reduced, especially with the LaNi0.6Fe0.4O3-δ coating.
Syntheses of La1-XSrxMnO3 Nanopowders by Hydrothermal Method
Authors: Yun Juyeon , Lee JongWon , Song Rak-Hyun , Tai Weonpil
Published: October 2013

Lanthanum strontium manganese, LSM, has been considered as one of the most prospect materials for solid oxide fuel cell (SOFC) applications due to its high electrode activity for the oxygen reduction reaction, high electronic conductivity and chemical as well as mechanical compatibility with the established solid electrolytes. In this work, Sr-doped LaMnO3 was synthesized by hydrothermal method and the effect of Sr doping on lanthanum manganese (LSM) was investigated. The La1-xSrxMnO3 (0≤x≤0.4) nanopowders were prepared under different reaction conditions by hydrothermal syntheses. The synthesized nanopowders were characterized the crystalline by X-Ray diffraction. The microstructure and particle size of the nanopowders were analyzed by FE-SEM and intercept method. The particles size of LSM powders was approximately ~170nm when used KOH as a precipitant. The relative density of LSM was over 97% by Archimedes density method. The electrical conductivity of the sintered pellet was measured at 750°C in air by DC four point probe method, and the electrical conductivity was 21.3~63.85 S/cm. The physical and electrical properties of Sr-doped lanthanum manganese were discussed.
SOFC Sealing with Thermiculite 866 and Thermiculite 866 LS
Authors: Hoyes John Robert , Rautanen M.
Published: October 2013

This paper discusses the structure and properties of a compression seal, Thermiculite 866, that is providing excellent service with SOFC development groups around the world. That performance is ilustrated by data showing the robustness and durability of the seal achieved during extended testing by a customer in his stack. The paper then goes on to introduce a new material , Thermiculite 866 LS , that has been developed to allow stack sealing at very low gaskets stresses. The performance of the new material at 700 'C in simulated stack service is illustrated.
Ab Initio Calculation of the Defect Structure of Ceria
Authors: Martin Manfred , Zacherle Tobias , Schriever Annalena , De Souza Roger A , Grieshammer Steffen
Published: October 2013

We present a defect chemical treatment of ceria, CeO2-
δ¸ based on formation energies of point defects which we calculated using density functional theory within the GGA+U approximation. All possible defect charge states are considered. In addition we consider polarons, associates of polarons with oxygen vacancies and vacancy-vacancy repulsion. Using the above ab initio data we calculate KrögerVink diagrams and compare them to experimental data.
Determining Surface Chemistry and Vibrational Properties of SOFC Anode Materials Through Ab Initio Calculations
Authors: Parkes Michael , Refson Keith , d'Avezac Mayeul , Offer Greg , Brandon Nigel P. , Harrison Nicholas
Published: October 2013

Understanding the chemical processes that occur at the anode triple phase boundary (TPB) between Ni, YSZ and fuel molecules is essential in determining solid oxide fuel cell (SOFC) anode performance. With a growing interest in vibrational spectroscopy for studying such processes, the surface and vibrational properties of the materials nickel (Ni) and yttria stabilized zirconia (YSZ) are investigated using first principles atomistic simulations based on density functional theory and empirical potential models. The initial findings and the methodology followed to date are presented.