bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance and Stability of Nickelates Based Oxygen Electrodes for Solid Oxide Cells
Authors: Vibhu Vaibhav , Vinke I. C. , Eichel Rüdiger-A. , De Haart L. G. J. (Bert) 
Published: July 2021

The K2NiF4-type nickelates i.e. Ln2NiO4+δ
(Ln = La, Pr, Nd) and La1.5Pr0.5NiO4+δ
have shown promising behaviour as oxygen electrodes for solid oxide cells [1]. These compounds show high anionic bulk diffusion (D*) as well as surface exchange coefficients (k*), combined with good electrical conductivity and thermal expansion properties matching with those of other components (electrolyte, interconnect etc.) of the cell. In order to further enhance the physico-chemical properties, electrochemical performance of these nickelates as oxygen electrode, we performed the substitution of nickel by other transition element such as cobalt. Two compositions of Ln2Ni1-xCoxO4+
δ
(Ln = La, Pr, Nd) and La1.5Pr0.5Ni1-xCoxO4+
δ
(x=0.1 and 0.2) were considered (as higher cobalt containing nickelates are difficult to synthesize under air atmosphere) and completely characterized using several methods. Finally, the symmetrical half-cells (8YSZ/GDC/electrode) as well as single cells (Ni-YSZ/8YSZ/GDC/electrode) were prepared and electrochemically characterized using DC- and AC-techniques in the temperature range 700 - 900 °C.
The current-voltage characteristics of the single cells show an increase in the performance with increasing cobalt content in both SOFC and SOEC operation for Ln2Ni1-xCoxO4+
δ
(Ln = La, Pr, Nd) and La1.5Pr0.5Ni1-xCoxO4+
δ
electrodes. The best cell performance is obtained with 20% cobalt substitution for all four nickelates. However, the performance of Pr2Ni0.8Co0.2O4+
δ
(PNCO20), La1.5Pr0.5Ni0.8Co0.2O4+
δ (LPNCO20) and Nd2Ni0.8Co0.2O4+
δ
(NNCO20) are similar and far better than La2Ni0.8Co0.2O4+
δ
(LNCO20) [2,3]. For instance under SOFC operation at 900 °C, the maximum power densities obtained at 0.6 V are 1.8, 1.9 and 1.91 W.cm-2 for NNCO20, LPNCO20 and PNCO20 single cells, respectively. Under SOEC conditions, the cell current densities obtained at 900 °C with an applied voltage of 1.5 V are 3.0, 2.84 and 2.8 A.cm-2, respectively for PNCO20, LPNCO20 and NNCO20 single cells with 50% H2O and 50% H2 feed gas mixture. The performance of these electrodes are better than the commercial single cell containing state of art (La,Sr)(Co,Fe)O3 oxygen electrodes. Moreover a large improvement in durability is also observed for the single cells containing cobalt substituted nickelates.
Results including physico-chemical and electrochemical properties of these materials, electrochemical performance as oxygen electrode, long term stability under electrolysis conditions and post-test analysis (using SEM-EDX, XRD) will be presented and discussed in detail.

References:

[1] V.Vibhu et al., Journal of Energy Chemistry, 46 (2020) 62.
[1] V.Vibhu et al., Journal of Power Sources, 444 (2019) 227292.
[2] V.Vibhu et al., Journal of Power Sources, 482 (2021) 228909.
Lifetime Prediction and Rapid Design Evaluation of SteelCell® Stacks Using Advanced Multiphysics Modeling
Authors: Gawel Duncan , Leah Robert , Thandi R , Reade Gavin , Howlett Jack , Lawrence Nick , Mukerjee Subhasish , Selby Mark 
Published: July 2021

A major challenge in the development of SOC stacks designed for long operating lives of the order of 50-100kh is predicting through-life performance without running durability tests under a particular set of operating conditions for 5-10 years. Whilst this is ultimately necessary it is not practical for system design purposes. It is also very costly to have to repeat experimental validation for a change in operating conditions or a new generation of stack technology.
To address this issue Ceres Power has invested heavily in Multiphysics simulation capability for stacks using COMSOL Multiphysics, incorporating fluid dynamics, heat transfer, electrochemical and heterogeneous chemical reactions.
The multiphysics model has the capability to simulate multiple scales from a single cell to a full-size 5kW stack. Start-of-life cell performance as a function of temperature and fuel composition is calibrated from extensive high-resolution AC impedance measurements on button cells, with the predicted stack performance experimentally validated using highly instrumented stacks.
A further challenge in stack simulation is to simulate through life performance changes due to multiple cell degradation mechanisms, to predict stack life and through-life performance and efficiency. To address this issue, Ceres Power has invested significant effort into understanding mechanisms of performance degradation at the fundamental cell level, generating mathematical models of degradation as a function of time, temperature and current density. Most degradation mechanisms observed are common to all SOFCs cells, such as poisoning of both electrodes and increases in ohmic resistance due to oxide scale growth.
A pseudo-dynamic solver has been applied to the multiphysics model applying the models of cell degradation to be applied to a full stack, including a control loop changing the thermal boundary conditions through life to maintain a constant nominal stack temperature. To maintain tractable simulation times, most of the physics of the stack is treated as steady-state, with only those mechanisms changing over a timescale of hundreds to thousands of hours solved dynamically. Using this approach, tens of thousands of hours stack operation can be simulated in a few tens of hours of CPU time on a high-performance server even at the full 5kW stack scale.
The dynamic multiphysics degradation model has been validated against through-life performance tests. This is a powerful tool which allows rapid evaluation of the likely impact of operating a stack in a condition other than ones in which extensive test data already exist.
Effects of Flow Channel Arrangement and Electrolyte Thickness on Thermal Stress for Planar Solid Oxide Fuel Cell Stacks
Authors: Zheng Jianmin , Xiao Liusheng , Chen Ming , Yuan Jinliang 
Published: July 2021

Typical operating temperature for solid oxide fuel cells (SOFC) is between 700~800°C. A large temperature gradient and thermal stress caused by internal losses and electrochemical reactions may cause SOFC stack performance degradation and even structural damage, which has become a hindrance to its applications.
In this study, a three-dimensional multiphysics CFD (computational fluid dynamics) model is developed and applied for a planar SOFC stack to study the temperature and thermal stress distribution, as well as effects of structure and design parameters, including the flow channel arrangement (e.g., co- and count-flow) and thickness of the electrolyte layer. The stack is composed of three-unit cells, metallic interconnect layers, sealing and anode/cathode current collectors.
The simulation results reveal that the temperature difference in the counter-flow mode is smaller and the thermal stress is lower than those in the co-flow mode. The overall performance of the stack is better when the electrolyte layer thickness becomes smaller, but the stack temperature and the temperature gradient become higher. In addition, a large temperature gradient due to the thin electrolyte layer leads to a significant increase of the thermal stress in the electrolyte. The findings and research method from this study can be applied to optimize the design of the stack structures, by consideration of the maximum thermal stress and its distribution.
Acknowledgements
This work is supported by the National Key Research and Development Project of China (2018YFB1502204), the Ningbo major special projects of the Plan “Science and Technology Innovation 2025” (2018B10048).
References
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Figure 1
First-Principles Calculation and Multi-Scale Observation for a Carbon Deposition on a SOFC Anode Near the Interface
Authors: Watanabe Hirotatsu , Ogura Teppei , Hanamura Katsunori 
Published: July 2021

The nickel/yttria-stabilized zirconia (Ni/YSZ) and nickel/scandia-stabilized zirconia (Ni/ScSZ) have widely used as an anode for solid oxide fuel cells (SOFCs). The high operation temperature allows an SOFC to operate on a wide range of fuels, including hydrocarbons and coal syngas. Ni is also a catalyst for carbon deposition reactions which destroy the anode microstructure. Meanwhile, the carbon deposited on the electrode can be used for different ways. It is important to control the carbon deposition on the electrode; therefore, the carbon deposition model needs to be developed.
In this study, carbon deposition site in the Ni/YSZ and Ni/ScSZ was studied through first-principles calculation and multi-scale observation using SEM and TEM. Observation showed that the carbon deposition was progressed not in the overall Ni surface but in the specific sites such as the interfaces and Ni(211) facet at low temperature. The carbon deposition rate strongly depended on the electrode structure at microscales. All calculations here are performed employing the periodic density functional theory (DFT) method implemented in the Vienna Ab-Initio Simulation Package (VASP). The Ni/YSZ and Ni/ScSZ atomic models are developed to discuss the CH adsorption which is the initial step of the carbon deposition. The CH adsorption energy in the concentrated vacancies at the Ni/YSZ interface was much lower than that in the Ni(111) facet, indicating that concentrated vacancies become the active site of the carbon deposition. However, the CH adsorption energy in the dispersed vacancies are almost the same as that in the Ni(111) facet. It is shown that vacancy patterns play an important role in the carbon deposition rate. The impact of dopant in the anode on the carbon deposition is also studied. DFT calculation gives an useful hint to develop the carbon deposition model with considering the electrode structure.
The Influence of Humidity Content on Ferritic Stainless Steels Used in Solid Oxide Fuel Cell Under Dual Atmosphere Conditions at 600°C
Authors: Gagliani Luca , Visibile Alberto , Gündüz Kerem Özgür , Svensson Jan-Erik , Froitzheim Jan 
Published: July 2021

In the last few years, the interest in the development and application of green energy harvesting, storage and production technologies, boosted the research activities to fulfill the demand of better performing, more reliable and cost-effective materials. In the field of Solid Oxides Fuel Cells (SOFC), many efforts have been spent on the interconnects, that are used to electrically connect single cells to obtain stacks for higher output voltages. Interconnects are exposed simultaneously to fuel gas (i.e., H2) and oxidizing (humid air) atmospheres (dual atmosphere) at a working temperatures in the range between 600°C and 800°C. Nowadays, chromia forming ferritic stainless steel (FSS) has been selected as material for interconnects due to its ease of fabrication, affordability and electrical conductivity. In air the material forms a protective chromia layer that reduces further corrosion. However, in dual atmosphere conditions, FSS commonly show fast and unexpected degradation, on the air side, especially at 600°C.
The mechanism behind the dual atmosphere effect is still not fully clear, but previous works highlighted the importance of pre-oxidation time, exposure temperature, humidity and surface finishing. Until now, major efforts have been spent in studying the long-term behaviour, with the aim to identify a long-lasting interconnect material. To successfully overcome the effects of dual atmosphere-induced corrosion, it is of fundamental importance to investigate how the corrosion phenomenon starts and evolves. In this work, the initial stages of dual atmosphere breakaway corrosion at 600°C were investigated for selected FSS alloys. The samples were exposed under controlled conditions which resemble those of SOFC (Ar-5%H2 + 3%H2O//FSS//air + 3%H2O). The oxide scales were further investigated by means of Scanning Electron Microscope (SEM) and Energy Dispersive X-ray (EDX) analysis. Experiments with different exposure times were performed (i.e., up to 12 hours) and the influence of temperature ramping was studied.
Several parameters were evaluated, like the effects of chromium content, the role of sample thickness and the influence of trace elements in different alloys and different batches of the same alloy. Implications of grain orientation at the surface, as well as of pre-oxidation treatment were investigated too.
Repair Joining of Glass-Ceramic Sealants for SOC Stacks
Authors: Gross-Barsnick Sonja , Malzbender Jürgen , Fang Qingping 
Published: July 2021

A new concept has been developed to repair leaking solid oxide cell (SOC) stacks. Conventionally, the stacks are joined with a glass-ceramic sealant before they are taken to operation. Once they start leaking through the sealant, they have become unusable. This approach aims to prevent the scrapping of valuable aggregates.
A composite sealing material composed of a glass matrix “H” based on the BaO-CaO-SiO2 system with yttrium-stabilized zirconia fibers as filler material was used for this study. The sealant tends to crystallize slowly at 800 °C forming a multi-component glass-ceramic of a finely dispersed microstructure. The melting temperature of the crystallized material was investigated by means of differential scanning calorimetry (DSC). Beside of the glass matrix powder which was crystallized by heating to 850°C and dwelling for 100 h, the state-of-art sealing material was used as green foils of the composite mixture with fibers. Sandwiched samples of two Crofer22APU plates of 50x50 mm² were joined with the two types of sealing materials, followed by forcibly breaking of the samples and repair joining at different temperatures between the onset and peak temperature of melting of the glass-ceramic obtained by DSC. Gas-tightness measurement was performed by helium leakage detection at room temperature and the broken samples were investigated by optical microscopy. The optimal thermal treatment parameters were chosen on behalf of gas-tightness and porosity. Cross-sections were prepared after repair joining at 930°C for 10 h and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) was carried out. The microstructure shows a high amount of residual glass phase with clusters formed of zirconia-silicate needles. The reaction zone to the steel is of a similar thickness in comparison to standard joining at 850°C, but is clearly delineated from the sealing material. Close to the three-phase boundaries of metal/glass/air a homogeneously distributed closed porosity is found while the pores have gathered to flattened enlarged voids in the middle of the joining gap.
The impact of these microstructural findings on the strength of the joints are now investigated by means of torsion shear tests on hour-glass shaped Crofer22H samples joined in a ring contour. The strength data will be compared to the standard joining procedure and thermally aged samples (800°C for 1000h). Meanwhile an upscaling of the joining geometry using dummy plates of the size of window frame design (H20-design) stacks was performed and the result of gas-tightness measurements will be reported. In case of successful repair of dummy plates, this promising concept will be proofed with a 20-layer stack (internal number: H2020-02), which showed measurable leakage through sealant after start-up procedure.
Improving Current Collection of Tubular Solid Oxide Fuel Cells
Authors: Feng Hai , Panthi Dhruba , Du Yanhai 
Published: July 2021

Solid Oxide Fuel Cells (SOFCs) are electrochemical devices with solid electrolyte materials that convert chemical energy in fuels into electrical energy. Tubular SOFCs (T-SOFCs) is one of the major SOFC configurations which has the advantages of good thermal conductivity, easy to seal and shorter start-up time. However, challenges remain in effectively collecting the current inside the tubular cells. Developing an efficient, easily applicable and cost-effective collector is imperative. The properties of a desired current collector are to: reflect the fuel cell performance, be able to withstand the fuel cell’s high working temperature environment, protect the fuel cell from damage, simplify the current collector application procedure, expand the contact surface between the tube and the current collector, and save cost.
We have designed a current collector and identified the materials for inside tube current collection with desired characteristics such as high temperature tolerance, low electrical resistance, and low cost. The research focused on the effectiveness of the current collector and its durability at various fuel cell operation conditions. The design achieved a peak power density at 0.7V of 0.21W/cm2 at the temperature of 700oC for a conventional tubular SOFC with material set of Ni+8YSZ‖YSZ‖LSM. Comparing to the general metal (nickel, silver) current collectors, the studied material can reduce the cost from hundreds of dollars per yard to $0.13/yard. The paper will discuss the design and the cost-effective material selection of the current collector which provides a potential path for the commercialization of tubular SOFC technology.
Electrochemical Characterization of Intermediate-Temperature Solid Oxide Fuel Cells with PVD-Coated Electrolyte
Authors: Solovyev Andrey , Burmistrov Ilya Nikolaevich , Rabotkin Sergey , Shipilova Anna , Yalovenko Dimitriy Vladimirovich , Semenov Vyacheslav , Bredikhin Sergey Ivanovich 
Published: July 2021

Intermediate temperature solid oxide fuel cells (SOFCs) working in the range of 600–800°C are interesting because they allow the expansion of the choice of materials that can be used, decrease system cost, and reduce the corrosion rate of system components [1]. The thickness of the electrolyte should be reduced, so reducing the area-specific resistance of the fuel cell for working in this temperature range. Physical vapor deposition methods, such as magnetron sputtering are used to produce thin-film electrolytes [2].
This work is an extension of our previous efforts focusing on scaling the technology of magnetron deposition of electrolyte to large-area cells [3]. It is known that area-specific resistance of small button cells is much less than that of industrial-sized planar anode-supported SOFC cells (10 cm×10 cm or greater). Such difference in ASR is due to large ohmic losses in a SOFC stack that are highly dependent on contact resistance at the cathode/bipolar plate interface. For example, the power density of our 10 cm×5 cm cell with magnetron sputtered yttria-stabilized zirconia (YSZ)/gadolinium-doped ceria (GDC) bilayer electrolyte and La0.6Sr0.4Co0.2Fe0.8O3/Gd0.1Ce0.9O1.95 (LSCF/GDC) cathode was 430 mW/cm2 at 0.7 V and at 750°C [4]. This value was about 40% of that of the 2 cm diameter button cell (1025 mW/cm2) with a similar structure and composition. The area-specific resistance of the former cell was 0.54 Ohm·cm2, while it was 0.2 Ohm·cm2 for the latter one.
The goal of this work is to increase the performance of the large-area cell with PVD-deposited electrolyte by improving the structure and composition of the cathode active and contact layers. 4-µm-thick YSZ electrolyte and 2-µm-thick GDC barrier layer were deposited on the 5 cm×5 cm commercial NiO/10ScCeSZ anodes (KCERACELL CO., Korea) by means of reactive magnetron sputtering. LSCF/GDC cathode active layer with an active area of 4 cm×4 cm was screen printed onto the electrolyte. Electrochemical investigations were performed in the temperature interval of 600–800 °С. Figure shows the resulting performance – I–V–P curves of the large-area (5 cm×5 cm) cell with PVD-deposited electrolyte. High power densities of 0.29, 0.55, 0.83, 1.16 и 1.4 W/cm2 were achieved at 0.7 V and at 600, 650, 700, 750 and 800°C, respectively.
Acknowledgements. This work was funded by the Russian Science Foundation (Grant No. 17-79-30071).
[1] D. J. L. Brett et al., Chem. Soc. Rev., 37, 1568 (2008)
[2] S. Sønderby et al., Surf. Coat. Technol., 240, 1 (2014)
[3] A. Solovyev et al., J. Electrochem. En. Conv. Stor., 15(4), 044501 (2018)
[4] A. Solovyev et al., Fuel Cells, 17(3), 378 (2017)

Figure 1: I–V–P curves of the large-area (5 cm×5 cm) cell with PVD-deposited electrolyte.

Figure 1