bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coke Resistant and Sulfur Tolerant Ni-based Cermet Anodes for Solid Oxide Fuel Cells
Authors: Li Meng , Hua Bin , Jiang San Ping , Li Jian 
Published: February 2020

Conventional Ni-based cermet anodes of solid oxide fuel cells (SOFCs) are highly susceptible to deactivation from carbon deposition and sulfur poisoning in sulfur-containing hydrocarbon fuels. Here we propose a viable approach to substantially enhance the carbon deposition resistance and sulfur tolerance of the Ni-gadolinia doped ceria (Ni-GDC) anode. Perovskite BaCe0.9Yb0.1O3-
δ (BCYb) is adopted to modify Ni-GDC anode via wet impregnation. Since BCYb nanoparticles could selectively deposit on Ni surfaces in a Ni-GDC anode backbone, a slight amount of infiltrates could lead to the excellent modification of the Ni grains without blocking the gas diffusion channels. The deposited BCYb nanoparticles decrease the exposed surfaces of Ni grains, showing promise to inhibit carbon deposition and sulfur species adsorption. BCYb has high oxygen ion conductivity, beneficial to the transportation of oxygen ions to remove the adsorbed carbon and sulfur (Fig. 1). Therefore, the stability of conventional Ni-GDC anode in wet methane fuel (3% H2O in CH4) is remarkably improved with modification of BCYb nanoparticles. The voltage of a full cell with conventional Ni-GDC anode decreases rapidly from 0.58 to 0.15 V within 6 h at 200 mA cm-2 and 750 °C. While in the case of a cell with BCYb modified Ni-GDC anode, designated as B+Ni-GDC, the cell voltage is essentially constant at around 0.65 V over a period of 48 h tested under identical conditions. Furthermore, the impregnation of BCYb nanoparticles can also improve sulfur poisoning resistance of Ni-GDC anode. The enhanced stability is observed in 500 ppm of H2S/H2 at 650 °C. The B+Ni-GDC anode manages to retain its microstructure in CH4 and H2S-containing H2 fuels, resulting in stable performance output. In addition, the electrochemical performance of Ni-GDC anode is also improved with BCYb modification in both wet H2 and CH4 fuels. The BCYb impregnation approach shows promising potential in the development of highly active and stable Ni-GDC based anodes for direct hydrocarbon SOFCs.
Figure 1. Schematic diagram showing carbon and sulfur removal processes on BCYb modified Ni-GDC anode.

Figure 1
Automated SOFC Design Exploration
Authors: Lueth Christopher A , Walchshofer Christian F 
Published: February 2020

Fuel cells are a clean alternative to internal combustion engines and many experts consider them to be the future of ground-transportation. Solid oxide fuel cells are already heavily used in Japan for clean energy grid storage applications. Unlike combustion of hydrogen and oxygen that only generates heat, electrochemical reactions of hydrogen and oxygen may be separated to harness ion and electron transport for high efficiency energy conversion.
We present computer automated engineering of fuel cell stack design to maximize power production and minimize energy losses. Validated cell models are applied to 3-D stack simulations, where optimization algorithms obtain better designs, faster. Each simulation conserves flow, energy, species, and charge transport using efficient sparse segregated solvers. Automated workflows and state-of-the-art search algorithms allow for fast design space exploration of fuel cell material properties, dimensions, and boundary conditions. Bibliography

[1]
O. R. J. G. a. J. M. V. Costa-Nunes, "Comparison of the performance of Cu–CeO 2–YSZ and Ni–YSZ composite SOFC anodes with H 2, CO, and syngas," Journal of power sources, vol. 141, no. 2, pp. 241-249, 2005.

[2]
F. Scholz, "Thermodynamics of electrochemical reactions," Electroanalytical Methods. Springer Berlin Heidelberg, pp. 11-31, 2010.

[3]
A. D. S. B. B. a. J. G. P. Le, "Validation of a Solid Oxide Fuel Cell Model on the International Energy Agency Benchmark Case with Hydrogen Fuel," Fuel Cells, vol. 15, no. 1, pp. 27-41, 2015.

[4]
S. G. Bratsch, "Standard electrode potentials and temperature coefficients in water at 298.15 K," Journal of Physical and Chemical Reference Data , vol. 18, no. 1, pp. 1-21, 1989.

Figure 1: In solid oxide fuel cells, hydrogen fuel diffusing through the porous anode (left) reacts with oxygen ions traveling across the electrolyte membrane separator (middle) and produce electrons conducting through the solid porous cathode (right). Power is generated by flow of electrons from anode through an external circuit to the cathode (top), where they recombine with oxygen, in the air feed diffusing through the porous cathode, to repopulate membrane oxygen ions.

Figure 1
Determination of Temperature and Fuel Utilization Distributions in SOFC Stacks with EIS
Authors: Tallgren Johan , Boigues Muñoz Carlos , Mikkola Jyrki , Himanen Olli , Kiviaho Jari 
Published: February 2020

Efficient operation of solid oxide fuel cell (SOFC) stacks requires uniform temperature and fuel utilization distributions in the stack. Especially high fuel utilizations (FU) necessitate uniform fuel flow distributions to avoid anode redox of the cell with the highest local FU. A uniform temperature distribution helps to prolong the life-time of the stack. Knowledge about such distributions would aid in both stack design and in monitoring the “state-of-health” of stacks. This work presents a method to determine the fuel utilization and temperature distribution in SOFC stacks with electrochemical impedance spectroscopy (EIS). EIS is a powerful and non-destructive technique that enables an in-depth analysis of the stack in-operando. The equations for relating the measured impedance and fuel utilization and temperature are derived from common equations describing the SOFC stack. Thus, the relations are anchored in physical processes. The method is demonstrated with an ElringKlinger AG 10-cell stack at nominal operation conditions. The difference in fuel flow, i.e. fuel distribution, and temperature between individual cells was determined. The temperature distribution exhibits a stack effect, where the top and bottom-most cells are the coldest, and is in line with the cell voltages. The paper evaluates the method and its usability in SOFC research.
The NELLHI (grant agreement no. 621227) and INNO-Sofc (grant agreement no. 671403) projects, which have received funding from the European Union’s Fuel Cells and Hydrogen Joint Technology Initiative, are acknowledged. Additionally, the STEP project, funded by the Finnish Funding Agency for Innovation TEKES and Projekträger Jülich (Germany), is acknowledged.
Short Stack Kit for the Open Flange™ Set-up Using Soft Mica Seals
Authors: Coquoz Pierre , Coton Noelia , Cottier Florian , Pappas André , Middleton Hugh , Ihringer Raphaël 
Published: February 2020

Fiaxell has been active since 2008 in the Solid Oxide Fuel Cells (SOFC) industry and has been developing components and products for SOFC research.
Fiaxell is the inventor of the “2R-Cell”, an anode supported cell able to withstand full re-oxidation and thermal cycles. The 2R-Cell is robust and has demonstrated high fuel utilization (85-90%) and electrical efficiency up to 50% with pure hydrogen on button cells.
Fiaxell has developed the Open Flange™ Set-Up in order to test SOFC and SOEC cells. The Set-Up allows researchers to do various experiments, such as current-voltage characteristics, polarization, impedance spectroscopy measurements, electrolysis, co-electrolysis and in situgas processing (POX, SR) thanks to its integrated steam generator.
Fiaxell is now offering a complete short stack kit that can be directly mounted onto the Open Flange™ Set-Up platform.
This kit allows researchers to perform a range of experiments and to study stack parameters such as flow distribution, electrical contact resistance, and to investigate protective coatings to avoid chromium evaporation, in situfuel processing and sealing gas tightness. Each parameter can be independently characterized and optimized by combining ideal and real stack conditions on both sides of the cell, for instance Crofer steel on the anode and gold mesh on the cathode.
Fiaxell is proposing Crofer 22H interconnects with different flow pattern designs for 50 X 50 mm and 80 X 60 mm cells. Alternatively, customers can propose their own customized design which can then be chemically grooved and laser cut by Fiaxell. The short stack kit comes with soft mica sealing but can also be made gas tight with any glass paste or other sealants. The soft mica seals have been designs to be easily removed and replaced, contrary to the use of glass based sealants that require mechanical grinding to remove.
Mechanical simulations and calculations have been made to ensure that the design of the end Flange™ is adequate to compress the entire stack without any distortion or stress concentration points, especially on the interconnect plates.
In order to see the gas distribution in the interconnect pattern, Fiaxell has developed an alternative, and complementary method to simulation, which consists of direct visualization and image analysis of the real flow motion. Screen captures will be included and discussed.
In this paper, we present the experimental results of the short stack tests using two different interconnect patterns and also discuss the effectiveness of the soft mica gasket seals.
Image caption: Exploded view of
two
cells short stack showing the three bipolar plates (interconnect) and soft mica gaskets (in beige). The short stack has been designed as a kit to be integrated directly on the Open Flange™ Set-Up platform.

Figure 1
Sulfur Poisoning of Ni/CGO Anodes: A Long-Term Degradation Study
Authors: Riegraf Matthias , Costa Rémi , Schiller Guenter , Friedrich K. Andreas 
Published: February 2020

Although continuous progress is achieved with respect to lifetime and performance improvements, solid oxide fuel cells (SOFC) continue to struggle with commercialization. One important factor to possibly reduce overall costs of SOFC systems would be the omission of desulfurization units during the fuel processing. However, sulfur-containing impurities in the most common fuels such as natural gas and biogas lead to significant performance drops upon exposure to Ni-based anodes. In this regard, it has been shown that Ni/gadolinium-doped ceria (CGO) anodes display lower performance drops upon short-time sulfur exposure than Ni/YSZ. However, their long-term resistivity towards sulfur exposure has not been investigated so far, although this is likely to be the most vital factor determining SOFC lifetime.
This work presents the first in-depth analysis of long-term degradation due to sulfur poisoning of Ni/CGO10-based SOFC. A parameter study of the sulfur-induced long-term degradation of commercial, high-performance single cells was conducted with an accumulated cell testing time of more than one year. The long-term degradation behavior is investigated at 900 °C for different H2S concentrations and varying H2/H2O/N2 fuel gas atmospheres. The sulfur poisoning periods of the different cells varied from 100 up to 1500 h. The progress of the degradation during the experiments was monitored by means of electrochemical impedance spectroscopy.
It is shown that Ni/CGO anodes can be exposed to 10 ppm H2S and operated without significant irreversible degradation at a current density of 0.5 A·cm–2 for 1500 h for certain fuel gas mixtures, demonstrating their promising long-term stability. However, for reduced hydrogen partial pressures in the fuel gas, the same H2S concentration leads to a considerable voltage decrease that is reflected by an increase in anode charge transfer and ohmic resistance. Furthermore, the microstructural evolution of the Ni/CGO is examined ex-situ by means of SEM and correlated to the anode performance degradation. The existence of a stable operating regime for Ni/CGO anodes under sulfur exposure is clearly shown and the critical operating parameters are outlined. The presented results give important insights into the degradation processes occurring during long-term operation of Ni/CGO anodes as well as strategies for stable SOFC operation. Moreover, the results encourage to further optimize the performance and sulfur tolerance of Ni/CGO anodes.
Electrochemical Performance of Solid Oxide Electrolysis Cells with LSCF6428-SDC/SDC Electrode for H2O/CO2 High Temperature Co-Electrolysis
Authors: Yoo Young-Sung , Jeon Sang-Yun , Park Min-Ah , Lee Jungmin , Lee Younghee 
Published: February 2020

High temperature co-electrolysis of H2O/CO2on solid oxide electrolysis cell (SOEC) is one technology to produce syngas using carbon dioxide. In this study, Ni-8YSZ/8YSZ/LSCF6428-SDC button cells were fabricated and the effect of different heat treatment temperatures on the performance of SOEC was investigated. The SOEC with LSCF6428-SDC air electrode, SDC buffer layer, and YSZ-(LSCF- SDC) adhesion layer gave better performance in overall results and the voltage obtained for this SOEC at current density of 0.8 A.cm-1 was from ~ 1.2 V to ~ 1.8 V. Co-electrolysis and the electrochemical performance of the cells were dependent on heat-treatment temperature of the electrode and the buffer layers. To identify the electrochemical processes occurring at the electrodes of SOEC, analysis of the electrochemical impedance (EIS) data was carried out.
The Exploration of Working Reactions for Electrolysers Using Statistical Mechanics
Authors: Williams Mark C , Richards George , Gemmen Randall 
Published: February 2020

This brief thermodynamic analysis theoretically explores the performance of an electrolyser for various working reactions (WR). The electrolyser cell (EC) system is composed of an electrolyser and heat engines. The lowest electrical requirement for working reactions for electrolysis will have the highest possible Carnot temperature, Tc , and ∆T∆rS(T) values needed to minimize ΔG and maximize the amount of thermal that could be converted to chemical energy in an electrolyser. In addition, reactions with multiple products and few reactants create additional entropy, that is, many high entropy products coming from a few low entropy reactants, are optimal. A procedure using statistical mechanics was developed and employed to locate optimal WR’s focused on the values of ΔrSo, Tc, and the number of products and reactants. The research and development direction for electrolyser WR’s is discussed.
Long Term Tests of Ni-YSZ|YSZ|GDC|Pr0.6Sr0.4CoO3-δ in SOFC and SOEC Regimes
Authors: Nurk Gunnar , Kukk Freddy , Kanarbik Rait , Möller Priit , Lust Enn 
Published: February 2020

Stability of electrochemical performance in time is one of the most important properties of SOFC/SOEC materials looking from the commercialization point of view. Long term characterization is resource consuming and therefore only commercially more interesting compositions are tested in time range of several thousand hours [1]. However, for better understanding of reasons and mechanisms of degradation processes alternative materials should also be tested in addition for the more attractive ones.
Pr0.6Sr0.4CoO3-δ (PSC) is an alternative material for widely used La0.6Sr0.4CoO3-δ
with excellent activity as medium temperature SOFC cathode. However, so far there is lack of long-term test results for PSC. This study concentrates on the long term electrochemical characterization and microstructural post-test analysis of Ni-YSZ|YSZ|GDC|Pr0.6Sr0.4CoO3-δ
5 × 5 cm single cell, where YSZ is the yttria stabilized zirconia and GDC is the gadolinia doped ceria. Performance test conducted in SOFC mode at 650 °C and at cell potential 0.85 V was 17820 h long. Initial degradation of electrochemical performance was 2.6 % per 1000h. During second half of experiment degradation was only 1% per 1000h. Total power loss during test was 34.6 %. Moderate increase of total activation energy Etot at 0.8 V cell potential takes place (ΔEtot = 0.38 eV) and it increases from 0.57 eV to 0.95 eV. At 1V cell potential ΔEtot = 0.22eV, from 0.34 to 0.56 eV. Post mortem HR-SEM and TOF-SIMS analysis of tested cell has been performed and collected data show that minor structural changes caused by nickel coarsening in porous anode have been taken place. TOF-SIMS mappings of 5 × 5 cm electrode visualize the mobility of Sr from cathode into the electrolyte interface during electrode preparation. Some mobility of Si from gas-sealing glas to electrode as well as Cr deposition from Crofer 22APU current collector into electrode surface has been established.
[1] L. Blum, U. Packbier, I. C. Vinke, L.G. J. de Haart, Fuel Cells,
13 (4) 646-653
Performance Characterization of Glass-Ceramic Sealants in Dual Atmosphere Environment for Reversible Solid Oxide Cell (R-SOC) Applications
Authors: Ferrero Domenico , Sabato Antonio Gianfranco , Javed Hassan , Lanzini Andrea , Herbrig Kai , Walter Christian , Santarelli Massimo , Smeacetto Federico 
Published: February 2020

Reversible Solid Oxide Cells (RSOCs) are a promising technology for electrical energy storage through hydrogen – a flexible multi-purpose energy carrier. A key component of planar stacks of cells is the sealant joining the cell to the interconnect, which must be chemically and physically stable and ensure gas tightness between oxidizing (air) and reducing atmospheres (H2).
Novel glass-ceramics compositions for a working temperature of 850 °C were designed and characterized in terms of sintering capability, thermal and thermomechanical properties. Crystalline phases and different amounts of residual glassy phase were tailored in order to assure a good thermomechanical compatibility with a Crofer22APU interconnect. The gas tightness of the glass-ceramic sealant has been tested in a dual atmosphere environment at 800 °C and nearly atmospheric pressure. Samples comprising of two plates of interconnect material (Crofer22APU) have been joined together by the sealant and have been exposed to air on one side and H2/steam on the other side to investigate the gas leakage rate through the sealant. The leakage rate has been evaluated by measuring the volumetric gas flow rate at the outlet of each chamber. The gas tightness of the sealant has been tested in relevant RSOC conditions at different pressure gradients between the two atmospheres (from 5 mbar to 50 mbar), flow rates and H2/H2O ratios.
The compatibility between the glass-ceramic sealants and the Crofer stainless steel (bare and pre-oxidised) is reviewed and discussed by means of SEM and EDS analysis before and after the dual atmosphere tests.
A Reactive Force Field (ReaxFF) for Molecular Dynamics Simulations of NiO Reduction in H2 Environments
Authors: Oberhoffer Simon , Iskandarov Albert M , Umeno Yoshitaka 
Published: February 2020

Ni/YSZ cermet is a widely used SOFC anode material, particularly due to its combination of good electric conductivity, high catalytic activity and low cost. Nonetheless, Ni/YSZ cermet anodes are facing unique challenges such as nickel agglomeration and reoxidation, eventually resulting in anode degradation. A solution to these problems might be obtained via a better comprehension of the underlying manufacturing processes, particularly the final H2-induced reduction reaction of NiO to Ni. Experimental approaches have contributed immensely toward a better understanding of these phenomena, yet are generally limited in terms of spatial and temporal resolution, thus motivating us to investigate the problem from a multiscale simulation viewpoint. In this study, we developed a reactive force field (ReaxFF) for nickel/oxygen interactions, which was specifically tailored toward molecular dynamics (MD) simulations of NiO reduction in H2 environments. The force field parameters were derived by fitting the ReaxFF energies and forces of various nickel/oxygen structures to the respective values of first-principles calculations. The structures considered here include bulk NiO, Ni2O3 and Ni3O4 at various densities, NiO under shear, the NiO(100) surface, oxygen vacancies in bulk and surface NiO as well as oxygen adsorbed onto the NiO(100) surface. The developed force field was subsequently used to predict the reduction kinetics of nano-scale NiO crystals in a H2 atmosphere at different temperatures and hydrogen partial pressures. Here, we observed a significantly improved structural stability of bulk NiO at temperatures over 700 K, compared to our previous ReaxFF nickel/oxygen description [1] and similar ReaxFF parameter sets published by other authors [2]. Besides quantifying the reduction rate, further core phenomena such as the induction period before the onset of a steady state reduction process, the pore formation in NiO at lower temperatures, as well as the importance of oxygen vacancies during the reduction are discussed and compared with experimental results.

Fig. 1 NiO nanocrystal after 0.2 ns of MD reduction simulation at a global temperature of 850 K and hydrogen partial pressure of 10 bars, using our previous ReaxFF parameter set (left) and the parameter set introduced in this publication (right).

References

[1] Oberhoffer, S., Iskandarov, A., Umeno, Y., "Reduction of NiO in a H2 Environment: A ReaxFF Molecular Dynamics Study",2016 Asian SOFC Symposium (2016.09.04-07), The University of Tokyo, Japan.
[2] Zou, C., Shin, Y. K., van Duin, A. C., Fang, H., Liu, Z. K. "Molecular dynamics simulations of the effects of vacancies on nickel self-diffusion, oxygen diffusion and oxidation initiation in nickel, using the ReaxFF reactive force field.", Acta Materialia 83 (2015): 102-112.

Figure 1
Engineering FEA Sintering Model Development for Metal Supported SOFC
Authors: Chatzimichail Rallou , Dawson Richard , Green Sarah , Sullivan Daniel , Mukerjee Subhasish , Selby Mark 
Published: February 2020

Ceres Power is continuing to make excellent progress in the development of its low-temperature metal supported SOFC design (the ‘Steel Cell’) based predominantly around the use of ceria. This unique design architecture allows for a robust, low cost, subsidy free fuel cell product, whilst retaining the advantages of fuel flexibility, high efficiency and low degradation.
Predicting the thermal stress and deformation evolution during processing is important in the design and manufacture of metal supported SOFC. This leads to reduced waste during manufacturing and feeds into cell and stack designs to produce low stress and mechanically robust modules for high performance and excellent durability.
In a collaboration between Ceres Power and Lancaster University, funded by Innovate UK, an engineering FEA model is being developed to understand the manufacturing processes, such as the densification of the ceria based electrolyte. In such models material properties, such as the Thermal Expansion Coefficient, Young’s Modulus, layer densification rates and creep, are very important. These properties, when interacting with the applied thermal processes, give rise to stresses within the layers resulting in permanent deformation and residual stresses at the end of the process step at room temperature.
We will present results using the developed modelling techniques in example metal supported SOFCs to demonstrate the importance of the above mentioned properties. Sensitivity study results will be also presented to show the impact of variability of the material properties.