bluuebunny/crossref_metadata_2025_split huggingface dataset:
In-Situ Observation of Co-Ce Coated Metallic Interconnect Oxidation Combined with High-Resolution Post Exposure Analysis
Authors: Poitel Stéphane , Wang Zhujun , Willinger Marc , Van herle Jan , Hébert Cécile 
Published: February 2020

Several SOFC metallic interconnect coatings are based on cobalt, which is efficient to prevent chromium evaporation and to maintain the contact resistance low after prolonged exposure. The addition of a very thin cerium layer beneath the Co coating seems to reinforce its properties. The oxidation of such coated SOFC FeCr steels, which contain a considerable number of alloy additives, becomes difficult to interpret.
In this study, surface oxidation of Sanergy SSHT steel with Ce-Co coating, frequently used as interconnect material, was first observed at high temperature (900°C) under an oxygen flow, in a modified environmental scanning electron microscope (ESEM), for different durations (0-48h). After these live observations, lamellas of the observed area were precisely cut using a focused ion beam (FIB). This allowed to evaluate the final composition of the oxidation layers of the steel by scanning transmission electron microscopy (STEM) and energy dispersive x-ray analysis (EDX), to try to link the chemistry to the structures observed during in-situ observation in the ESEM.
In-situ observation up to 48h was conducted. Results show the diffusion of manganese towards the cobalt coating to form a cobalt-manganese spinel oxide layer. Under this top layer, chromia scale forms. The very thin cerium layer does not prevent the diffusion of other elements from the steel. Niobium and titanium form oxidized precipitates in the steel just below the chromia scale.
Results from shorter exposure/observation times present a time-lapse picture of the initial oxidation for a more detailed understanding. Ex-situ experiments complement the results.
Influence of the Bias Substrate Power on the GDC Buffer Layer
Authors: Breaz Elena , Aubry Eric , Billard Alain , Coton Noelia , Coquoz Pierre , Pappas Andrée , Diethelm Stefan , Ihringer Raphaël , Briois Pascal 
Published: February 2020

Nowadays, the researchers that are working on the SOFC technology, are agree that it is necessary to decrease the operating temperature at 700°C(650-750 °C) of IT-SOFC technology, which currently is around 850-900°C for electrolyte supported cell used by the three main operators –Bloom, Hexis and Sun Fire. At this temperature the reactivity and the component cost of the cell decrease. Nevertheless, some interactions between the conventional electrolyte material (YSZ) and the cathode material (lanthanum based) are still present and it is necessary to include a ceria buffer layer to avoid the possible formation of an insulating pyrochlore structure La2Zr2O7 layer at the electrolyte-cathode interface. In ceria family, the best material regarding the ionic conductivity is the samaria doped ceria. However, the gadolinia doped ceria is the most employed from the cost point of view and the availability of gadolinium in comparison with samarium. This buffer layer avoids the reactivity between electrolyte and cathode, and presents a good anionic conductivity. It must be dense, thin and adherent on electrolyte, in order to be suitable for the surface treatment process.
In this paper, we present some recent results obtained on the gadolinia doped ceria coatings deposited by magnetron sputtering from metallic targets in argon-oxygen reactive gas mixtures with different substrate bias voltage. After a description of the experimental device, a first part will be dedicated to their chemical, microstructural and structural characterization (SEM, XRD,…) in relation with the magnetron sputtering deposition parameters. In a second part, the ionic transport characteristics of the half cell (Ni-YSZ/YSZ/GDC) will be investigated via impedance spectroscopy measurements performed at various temperatures up to 800°C under Ar-H2 gas mixtures. Finally, a complete cell test ((Ni-YSZ/YSZ/GDC/LSC) was performed with the Fiaxell Open Flanges test bench.
This study is carried out within the framework of the European territorial cooperation program INTERREG V A France-Switzerland. It has benefited from financial support from the EU through the European Regional Development Fund (ERDF- € 139,176) and the Swiss Confederation's contribution of CHF 134,173
Solid Oxide Electrolyzer Stack with 20,000 h of Operation
Authors: Fang Qingping , Blum Ludger , Menzler Norbert H. , Stolten Detlef 
Published: February 2020

One of the critical challenges for application of solid oxide cell (SOC) technology is the long-term stability of the complete system and/or single component. Despite of different debating accelerating methods, the time and cost consuming endurance tests of stacks and cells under relevant conditions are still necessary for reliable degradation analysis and lifetime prediction. In parallel to the stationary solid oxide fuel cell stack tests (>34,000 h), a test with a two-layer solid oxide electrolyser stack in JÜLICH’s F10-design was started on September 2014 (still in operation as of 26.01.2017). The short stack consists of Ni/YSZ-supported cells (ASCs in fuel cell mode) with LSCF air electrode (La0.58Sr0.4Co0.2Fe0.8O3-δ) and 8YSZ (8 mol-% yttria-stabilized zirconia) electrolyte. A gadolinium-doped ceria (GDC) (Ce0.8Gd0.2O1.9) barrier layer was deposited between 8YSZ and LSCF by means of physical vapor deposition (PVD).
The stack was mainly characterized in a furnace environment in electrolysis mode, with 50% humidified H2 at 800 °C. The endothermic electrolysis operation was carried out with a current density of -0.5 Acm-2 and steam conversion rate of 50%. Electrolysis at lower temperatures (i.e. 700 °C and 750 °C) and fuel cell operation (with 0.5 Acm-2 and fuel utilization of 50%.) at 800 °C were also carried out shortly (<2000 h each) for comparison. After altogether ~20,000 hours of operation, the voltage and ASR degradation rates during electrolysis at 800 °C (8000~20,000 h) are ~0.4%/1000h and 3%/1000h, respectively. Electrochemical impedance spectroscopy (EIS) and analysis of the distribution function of relaxation times (DRT) showed that the degradation was primarily due to the increase in ohmic resistance. An increasing polarization in fuel electrode in one of the layers was also observed during the last 2000 h of operation, most likely due to the increased leakage rate inside the stack.
The stack is planned to be operated for another 2000 h before post mortem analysis. Stack performance and degradation analysis under different working conditions, together with preliminary post analysis will be presented.
Field Demonstration of a Novel Reversible SOFC System for Islanded Microgrid Energy Storage
Authors: Mermelstein Joshua , Cannova Catherine , Cruz Michael , Anderson Bill 
Published: February 2020

The high cost and energy security of importing fuel to islanded grids and communities has led to a growing need to generate power onsite with alternative and renewable energy technologies while reducing logistics costs of importing electrical power. The ability to provide independence, endurance, reliability, and resilience of power compels both remote and critical infrastructure loads to integrate greater capabilities into their microgrid systems. However, grid operators are being faced with the challenges of variability and intermittent energy production from renewables. Therefore, energy storage has become a critical component to balance micro and utility grids, improve efficiency, reduce fuel consumption, enable localized grid independent energy secure power in cases of emergencies or unreliable traditional grid use, and provide critical power in the event of power outages. There has been particular interest in reversible solid oxide fuel cells (RSOFCs) in the energy sector for electricity, energy storage, grid stabilization and improvement to power plant system efficiency due to favorable thermodynamic efficiencies of high temperature steam electrolysis. With funding from Naval Facilities Engineering Command and Expeditionary Warfare Center (NAVFAC EXWC), Boeing’s Advanced Technologies Program, using Sunfire fuel cell technology, has developed the largest ever fully integrated grid tied RSOFC system that uses sunlight and sea water to generate and store energy with no logistical tail. In this system, excess grid energy or curtailed power generated by renewables is sent to the system operating in electrolysis mode to produce H2. The H2 is stored and then used in the system’s fuel cell mode to provide supplemental power to the grid during peak hours or as needed. The system was designed to run off of sea water for cooling and water feed for electrolysis via an internal desalination unit or via the water recycle system. As part of this program, Boeing has developed a H2 storage and compression system, power distribution system, and master controller to interface with the fuel cell subsystem developed by Sunfire. Previous results showed that the system exceeded expectations with an electrolysis efficiency of > 80% LHV and an overall system efficiency of 60% LHV with compression and liquid water feed. The system has been shipped to Pearl Harbor on the island of Oahu, Hawaii to undergo a 6 month demonstration in the field on a working island microgrid. The intent of this demonstration is to validate the opportunity to insert reversible fuel cell systems with greater power generation (e.g. up to 1 MW) into microgrids on both remote islands and expeditionary applications. This paper will discuss test results and challenges of demonstrating a RSOFC system in island microgrid environments. It will also discuss how the RSOFC system fits into the overall microgrid concept for NAVFAC and helps to address a logistic free hydrogen economy in remote areas.
LaNi0.6Fe0.4O3 as Cathode Contacting Material: Effect on Anode Supported Cell Performances
Authors: Spotorno Roberto , Piccardo Paolo , Costa Rémi , Han Feng , Schiller Guenter 
Published: February 2020

In planar solid oxide fuel cell (SOFC) stacks ohmic losses are introduced at the interface between the electrodes and current collectors, especially in the cathodic compartments, due to the contact inhomogeneity. The porosity of the electrodes and geometrical issues linked to the shape of the interconnects are factors resulting in the reduction of the contact surface between such components. Contacting layers are often applied between the cathode and the interconnect in order to minimize such issues ensuring a uniform current collection along the electrode area. This leads to proper operation of the cells increasing the performances in terms of power output and mitigating their degradation rate.
In this work, LaNi0.6Fe0.4O3 (LNF) powders have beensynthesized by sol-gel methods and used to prepare a contacting paste. A testing setup, developed to test anode-supported cells with different contacting geometries, has been used to investigate the effect of LNF contacting paste between the cathode and the current collector. The cell performances revealed comparable results compared to those measured using a state-of-art La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) contacting paste, even showing better stability over time. Cell performances have been investigated by means of current-voltage curves. Electrochemical impedance spectroscopy has been used to distinguish the loss contribution within the investigated system and to measure their evolution over time. To confirm the observed performance evolution, microstructural changes and migration of elements have been characterized post-experiment by means of scanning electron microscopy-energy dispersive X-ray and X-ray diffraction techniques.
Changes in SOFC Cathode Crystallographic Structure Induced by Oxygen Deficiency in Cathode Room
Authors: Kivi Indrek , Aruväli Jaan , Nurk Gunnar , Lust Enn 
Published: February 2020

Stationary solid oxide fuel cell systems (SOFC) are highly efficient chemical energy conversion systems generating electricity and high quality heat. SOFC devices should be usable during over 40 000 hours and at least 100 thermal cycles. In this study, the changes of unit cell of cathode materials as a function of current density, p
O2 and temperature were analyzed as a risk factor to increase the degradation rate of cathode electrode, during the cell working time.
Reversible changes in the lattice parameters of SOFC cathode were observed depending on the temperature (T) and oxygen partial pressure (p
O2) applied. The cathode potential, T and p
O2 noticeably influences the unit cell volume, thus, the oxygen stoichiometry and concentration of vacancies.
The electrode structure (porosity) has strong influence to the change kinetics of crystallographic parameters of cathode at in-situ element operating conditions. By polarizing the cathode electrode cathodically, the activity of electrode increase and the molecular oxygen concentration near the electrode surface decrease. Decrease of oxygen concentration in the porous cathode matrix causes the expansion of lattice parameter of cathode material. The electrode material (LSC and GSC) lose oxygen, Co4+ reduces to Co3+ and because of that unit cell expands.
Only slight influence of oxygen partial pressure and potential to the crystallographic parameters of LSM (La0.6Sr0.4MnO3
−
δ) was registered. At the same time for LSC (La0.6Sr0.4CoO3
−
δ) and GSC (Gd0.85Sr0,15CoO3
−
δ) the crystallographic unit cell volume was a function of electrode polarization as well as the oxygen partial pressure. There is no remarkable vacancy formation detectable with HT-XRD in LSM cathode lattice caused by electrode polarizations applied.
Thermochemical crystallographic expansivity study of LSM, LSC and GSC cathodes with in-situ HT-XRD method gives valuable experimental data about the crystallographic changes caused by changes in operating parameters like cell potential, temperature, and oxygen partial pressure in cathode compartment and therefore helps to understand thermomechanical and degradation behavior as well as redox behavior of B site element (Co) as a function of different conditions applied for SOFC cathode.
Figure 1. Selected segment from XRD pattern for LSCO and GSCO cathode at electrode potentials 0 and -0.9 V vs Pt/Pt/O2, respectively.

Figure 1
Fabrication and Characterization of High Performance Intermediate Temperature Micro-Tubular Solid Oxide Fuel Cells
Authors: Ren Chunlei , Gan Yun , Lee Myongjin , Yang Chunyang , He Fei , Jiang Yanmei , Dong Guohui , Green Robert , Xue Xingjian 
Published: February 2020

A phase inversion-based dual-layer co-extrusion approach was advanced to fabricate micro-channel array structured micro-tubular
solid oxide fuel cells (MT-SOFCs). The inner graphite layer was used as a sacrificial layer to eliminate the middle sponge-like layer
and inner surface dense skin layer,which were normally formed using the single layer extrusionmethod. As a result, themicro-channel
array generated in the outer layer was a more open structure and facile fuel/gas diffusion was obtained. The fuel/gas permeability of
such an anode substrate Ni-Ce0.8Sm0.2O1.9 (Ni-SDC) was ∼9 times that of an anode substrate fabricated using the phase inversionbased
single layer extrusion method. The open circuit voltages (OCVs) of the corresponding cell Ni-SDC/SDC/PrBaCo2O5+δ were
0.89 V–0.85 V at 500–600◦C, much higher than those of other SDC electrolyte based MT-SOFCs. The peak power density of the
cell was ∼1484 mW cm−2 at 600◦C, approximately 1.5 times that of a similar cell with an anode substrate fabricated from the single
layer extrusion method. This is also the highest performance among the SOFCs with the same material system in open literature.
The fuel utilization rate was also significantly improved in different degrees depending on the supplied inlet fuel flow rates.
Fabrication and Electrochemical Characterization of Freeze-Cast Tubular Solid Oxide Fuel Cells
Authors: Du Yanhai , Persky Joshua , Zhao Kai , Ilkhani Hoda , Woodson Theo , Emley Benjamin , Hedayat Nader 
Published: February 2020

NASA and others have shown improved power density of planar solid oxide fuel cells (P-SOFCs) fabricated via the freeze casting technique. As a manufacturing process, freeze casting is capable of producing ceramic, metal, and cermet components with unique and tailorable microstructural features that enhance SOFC performance. Low thermo-cyclic durability and slow startup times are common problems for P-SOFCs and have similarly limited the development of freeze cast P-SOFCs. Tubular SOFCs (T-SOFCs) have demonstrated superior thermal cycling capability and relatively fast startup times but have been reported to have lower volumetric power density compared to P-SOFCs. The utilization of freeze casting for fabrication of tubular geometries is suggested as a solution to significantly increase the volumetric power density of T-SOFCs by enhancing gas diffusivity and triple phase boundary reactions and to be at par or better than the power densities of state-of-art P-SOFCs.
This paper reports the fabrication and characterization of freeze cast tubular anode supports for SOFCs. NiO-8YSZ (nickel oxide yttria-stabilized zirconia) anode supports were fabricated using three methods: gelation casting, center pin method, and a freeze and drain method. Slurry rheology was modified for vertical dip coating, and a dual purpose freezing and drying chamber was designed and manufactured. The effects of slurry properties and process parameters were studied with respect to the resulting microstructures. The freeze and drain method was determined to be optimum for producing highly porous tubular anode supports with hierarchical, acicular or dendritic micro-pore channels. With an optimized freeze-drying cycle, drying time was reduced significantly with minimal residual moisture in the green bodies. Additionally, the electrochemical performance of the T-SOFCs with freeze cast anode was evaluated.

Figure 1
Novel SOFC Design with a Co-Sintered and Inert-Supported Cell Concept
Authors: Haeffelin Andreas , Njodzefon Jean-Claude , Matte Eric , Lupetin Piero 
Published: February 2020

The demand for energy-efficient, decentralized and environmentally friendly power production is expected to grow in the coming years. Solid oxide fuel cells (SOFC) have received much attention due to their wide range of applications. Cells with different designs (planar and tubular) and supports (electrolyte-, anode- or metal- supported) have been developed and intensively tested in terms of performance, degradation rate and lifetime. Still, technical improvement and especially the cost reduction are crucial factors to make SOFC attractive for the market.
In the framework of a public funded project, a novel SOFC-concept is evaluated that has advantages in terms of costs and lifetime. The cell is mechanically supported by an inert porous silicate layer on the air side and was designed to enable a one-step co-sintering process of the entire cell at temperatures between 1100 °C and 1300 °C (Fig.1). In this contribution, we present the current status of the cell performance in this novel SOFC concept. First investigations carried on co-sintered button cells showed very promising results, namely high OCV values and a power density up to 300 mW/cm² at 750 °C in pure hydrogen.
However, the impedance analysis of the cells points out that a further cathode optimization would be beneficial for the overall cell performance in the novel layout. An additional electrochemical and microstructural analysis of symmetrical cells with a LSM-YSZ cathode sintered on a silicate support showed that cathode properties [1], in particular the oxygen reduction reaction, are strongly influenced by the presence of the silicate during co-sintering, due to evaporation of transition metals from the substrate.

Figure 1
Toward Lower Temperature and More Efficient Solid Oxide Fuel Cell: The Effect of Gibbs Phase Rule on the Triple Phase Boundary
Authors: Reda Mahmoud 
Published: February 2020

Stationary SOFCs are source of green electricity to power future electrically powered vehicles. In SOFC the ionic conductivity determines the efficiency. It is obvious that a shift in the operating temperature of solid oxide fuel cells (from 1000 down to around 750–800 degree C) is desired. However, better electrolyte and electrode materials are required for lower temperature operation in order to maintain their high temperature performance. It had been known that both phase purity (single phase) and microstructure of, for example LSGM materials, depend on synthesis procedure and processing and, as a matter of fact, the synthesis of a pure single phase material is rather difficult [1,2].
Two important conclusions are the objective of this research work:
1-The cathode, anode or electrolyte become ionically conducting at a sharp phase transition temperature (the operating T of the SOFC). Below such T the materials loses its ionic conductivity [3]
2-The Gibbs phase rule (single phase and two components of the air) may be applied at the triple phase boundary (TPB) where the number of phases of the MIEC (single or two phases) are in contact with single and pure phase electrolyte [4].
1. Djurado, E. and Labeau, M., J. Europ. Ceram. Soc., 1998, 18, 1397–1404
2. Tas, A. C., Majewski, P. and Aldinger, F.,. J. Am. Ceram. Soc., 2000, 83, 2954–2960
3. S. Hall, Superionics: crystal structures and conduction process,.Rep. Prog Physics, 2004, 67, 1233-1314
4. S. B. Adler, Factors Governing Oxygen Reduction in Solid Oxide Fuel Cell Cathodes, Chem. Rev. 2004, 104, 4791−4843.
Electrochemical Performance and Stability of (La0.6Sr0.4)0.95Co0.2Fe0.8O3-δ Cathode Powders Modified by Atomic Layer Deposition
Authors: Torabi Alireza , Geary Timothy C , Barton Joseph , Willman Carl , Ghezel-Ayagh Hossein , Roeder Jeffrey F , Zeberoff Anthony F , Golalikhani Maryam , Van Buskirk Peter C , Huang Kevin 
Published: February 2020

For solid oxide fuel cell (SOFC) systems to become economically competitive, continuous development of new materials and processes is required not only to enhance SOFCs durability but also to reduce their cost. The cathode electrode is known to contribute the most to SOFC performance degradation and efficiency loss. In the case of strontium doped lanthanum cobalt iron oxide, it has been frequently suggested that strontium migration to the cathode surface under operating conditions plays an important role in the degradation. Recently, there have been extensive efforts to modify the surface of the cathode in order to improve the reliability. Most of these attempts have been focused on surface modification subsequent to the cell fabrication (e.g. infiltration). An attractive alternative is to modify the cathode powder surface prior to incorporating the powder into the SOFC. This approach would simplify the manufacturing flow, allowing a “drop-in replacement” of existing cathode powders, while potentially providing similar or even better performance enhancements.
In this work, commercial (La0.6Sr0.4)0.95Co0.2Fe0.8O3-
d (LSCF) powders have been modified by atomic layer deposition (ALD) using zirconia-, ceria- and hafnia-based oxides. The effect of coating thickness (number of ALD cycles) and dopant addition have been investigated. Morphology and porosity of sintered samples based on ALD coated powders and the pristine powder were found to be rather similar. On the other hand, the electrochemical performance of cathodes based on the ALD treated powders was significantly different from that of the unmodified cathode. This paper examines the details of electrochemical behavior of ALD modified and unmodified powders. Electrochemical impedance spectroscopy (EIS) analysis of symmetrical cells under air at 600-800 °C temperature range showed that high and medium frequency arcs were highly affected in ALD treated samples whereas the low frequency region stayed unchanged. The effect of surface modification of LSCF powders on durability of the LSCF-based cathode is under comprehensive assessment.