bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of Structural Degradation Effects in a Solid Oxide Fuel Cell after Long-Term Operation
Authors: Dellen Christian , Tardif Samuel , Purohit Ravi , Micha Jean-Sébastien , Guillon Olivier , Menzler Norbert H. 
Published: September 2023

The sustainable production of hydrogen as well as its re-conversion into electricity will be a key aspect in a future green energy environment that is depending on regenerative resources. In order to ensure the eminent position of solid oxide cells (SOC) in this future hydrogen economy their reliability and long-term performance still needs to be improved. Having this in mind, we performed detailed investigations on samples from cells that were operated for 100,000h to get a profound understanding of structural degradation effects after long-term operation.
The investigated samples originate from a two layer stack of fuel electrode supported solid oxide cells that were operated at 700°C and 0.5 A/cm2 in fuel cell mode. The cells consist of a Ni/Y-stabilized ZrO2 (YSZ) fuel electrode, a dense YSZ electrolyte layer, a Gd doped CeO2 (GDC) barrier layer and a La0.58Sr0.4Co0.2Fe0.8O3-d (LSCF) air electrode. Furthermore, an additional contact layer of La0.97Mn0.4Co0.3Cu0.3O3-d was applied on the air electrode surface and, in order to inhibit Cr-poisoning the interconnector material was coated with a manganese oxide layer by wet powder spraying. The stack represents the usual material status from 2009 when the stack operation has been starting.
In the post-test analysis the microstructure and chemical composition was investigated by scanning electron microscopy (SEM) in combination with energy dispersive X-ray spectroscopy (EDS). The EDS analysis revealed localized, correlated enrichments of Sr and Cr in the bulk of the LSCF air electrode as well as at the LSCF / GDC interface. Moreover, non-correlated, localized Co enrichments could also be detected at the LSCF / GDC interface. In order to get an insight into localized structural changes and to identify impurity phases after long-term operation Raman spectroscopy measurements were performed. Hereby, it was for example possible to visualize, in accordance with the EDS analysis, the formation of a SrCrO4 impurity phase on the LSCF air electrode surface as well as inside the bulk of the LSCF by running Raman measurements on the air electrode surface as well as on embedded and polished cross-section samples. To study the structural degradation in detail with high spatial resolution, additional µ-beam Laue diffraction measurements were performed at the CRG-IF BM32 beamline at European Synchrotron Radiation Facility (ESRF).
Degradation Behavior of MK35x Stacks with Chromium-Based Interconnects in Steam Electrolysis Operation
Authors: Riegraf Matthias , Szabo Patric , Lang Michael , Costa Rémi , Rothe Stefan , Megel Stefan , Kusnezoff Mihails 
Published: September 2023

The currently ongoing commercialization of high-temperature solid oxide electrolysis (SOEL) requires the understanding of the underlying dominant degradation mechanisms to enable continuous progress in reducing stack degradation rates.
In the present study, the degradation behavior of stacks with chromium-based interconnects (MK35x) and electrolyte-supported cells (ESC) developed at Fraunhofer IKTS is investigated. For this purpose, the initial electrochemical performance of 10-layer stacks was extensively characterized in various operating conditions in both fuel cell and electrolysis mode by electrochemical impedance spectroscopy (EIS). Degradation was evaluated during galvanostatic steady-state steam electrolysis operation over >3000 h in the temperature range of 800-825°C at a current density of -0.6 A cm-2, corresponding to a steam conversion rate of 75%. EIS analysis was used to separate the different loss contributions in the stack and showed that the ohmic resistance increase was the dominating performance degradation phenomenon. Moreover, electrochemical degradation rates in steady-state SOEL mode are compared to the ones in reversible mode with a daily cycling between electrolysis and fuel cell operation.
Post-mortem analysis was carried out with scanning electron microscopy (SEM) to correlate the observed degradation phenomena with microstructural and morphological changes. The observed low degradation rates demonstrate that MK35x are ready for scale-up, and the present work gives guidance for operation strategies and stack design to extend their lifetime even further.
Evaluation of Hydrogen Ions Flowing through Protonic Ceramic Fuel Cell Using Ytterbium-Doped Barium Zirconate as Electrolyte
Authors: Okuyama Yuji , Harada Yoshiaki , Mikami Yuichi , Yamauchi Kosuke , Kuroha Tomohiro , Shimada Hiroyuki , Yamaguchi Yuki , Mizutani Yasunobu 
Published: September 2023

Protonic ceramic fuel cells (PCFCs) are clean power generation devices that do not emit carbon dioxide, and generate electricity when protons (hydrogen ions) pass from the fuel electrode through the electrolyte to form water vapor at the air electrode. As a fuel cell, PCFC is expected to be a highly efficient fuel cell because it can operate at medium to low temperatures of around 600°C and no fuel dilution occurs. However, proton-conducting ceramics can conduct not only protons but also a small amount of holes, which can cause electron leakage and lower the power generation efficiency. Therefore, it is very important to understand the ionic and hole conductivity in a fuel cell.
To evaluate the electronic leakage of PCFC, the amount of proton current flowed in PCFC can be measured by an apparatus developed based on the electromotive force of an electrochemical cell using 10 mol% In-doped CaZrO3 (hydrogen sensor) and Y stabilized zirconia (oxygen sensor). Water vapor pressure on cathode was change when hydrogen ion passes thorough PCFC. The current of hydrogen ion can be determined by monitoring water vapor pressure. We measured the current of hydrogen flowing through protonic ceramic fuel cell using ytterbium-doped barium zirconate as electrolyte. Hydrogen ion and hole were found to leak at OCV at 700°C. Then electronic leakage was estimated form the current of hydrogen ion and external current. The electronic leakage was found to be suppressed with increasing electrolyte film thickness. On the other hand, no leakage of hydrogen and holes was observed at 500°C.
Strontium Free Cu-Doped La2NiO4 Oxides as Promising Oxygen Electrodes for Solid Oxide Electrolysis Cells
Authors: Karki Surendra B , Seymour Lorraine , Le Long , Coyle Christopher , Springer R , Escobar Julian , Meinhardt Kerry , Marina Olga A 
Published: September 2023

In this work, strontium-free oxygen electrodes for electrode-supported SOFC/SOEC cells were evaluated. Strontium is known to react with volatile Cr from the metallic interconnect to form Sr-Cr oxides at the surface of the electrode, thus reducing the cell performance. Strontium-free cobalt- or copper-doped nickelates, La2Ni1-xBxO4 (B = Co or Co; x=0.1-0.5) were synthesized using solid state synthesis method. The crystal structures of the oxides were studied by Rietveld refinement analysis of the powder X-ray diffraction data. Similar to the parent compound, the Ruddlesden-Popper (RP) La2NiO4 oxide, the Co- and Cu-doped compositions were confirmed to crystallize with the tetragonal crystal structure with I4/mmm space group.
The electrochemical performance of the La2Ni1-xBxO4 electrodes was studied using 1 inch in diameter button cells in SOEC mode and compared to that of cells with the state-of-the-art (La0.6Sr0.4)0.95Co0. 0.8O3-δ (LSCF)- ceria composite electrodes. The oxide inks were screen printed onto the pre-fired ceria barrier layers on the YSZ electrolytes. Short- and long-term tests were conducted at 650, 750, and 800oC with the Ni-YSZ hydrogen electrode exposed to 50-98% steam in hydrogen. Scanning electron microscopy with electron diffraction spectroscopy (SEM/EDS) was used to analyze the electrode microstructures before and after testing.
In general, the performance of the La2Ni1-xBxO4 electrodes was slightly lower than that of LSCF. However, the electrode microstructures were not optimized, and further improvements could be made. The Co-substituted nickelate performances showed some degradation in in time. Cu-doped nickelates exhibited more performance during the same tests and the degradation rate was insignificant. The composition with 20% Cu appeared to be more active as well as more stable.
The Coating Effect on Interconnect Materials After >10 Years of Furnace Exposures
Authors: Norrby Niklas , Li Shunyi , Stenström Mikael , Westlinder Jörgen 
Published: September 2023

One of the key components in the SOFC stack is the interconnect which requires versatile material properties for a proper functioning, e.g., high temperature corrosion stability, low ASR degradation and low chromium evaporation. At the same time, a high production capacity needs to be reached in order to fulfil the supply demand required for GW levels. The high production capacity is realized through Alleima AB’s production line with coil-coil physical vapor deposition of coated interconnects for SOFC and SOEC applications [1].
More specifically, Sanergy HT 441 is the standard material intended to be used as an SOC interconnect. The substrate is a ferritic stainless steel (ASTM 441) which is coated with thin layers of Ce and Co (<1 µm). The material can be coated on both sides using the same coating or with a different coating. At elevated temperatures the Co coating forms a protective (CoMn)3O4 spinel layer which drastically reduces Cr evaporation while the Ce layer improves the corrosion resistance by reducing the chromia scale growth at the coating/substrate interface and thereby maintaining a low and stable ASR over time.
Since long-term stability is a critical property for interconnects, Alleima has over the years gathered data from furnace samples and can thus present results where some samples have been exposed at elevated temperatures during >10 years. The main results include the effect of Ce thickness or choice of substrate on mass gain and subsequent chromia growth. Selected samples with coating elements different than Co have also been investigated. Samples have been further investigated using scanning electron microscopy for cross-sections, x-ray diffraction for characterization of phases and residual stresses as well as glow discharge optical emission spectroscopy for elemental analysis.

References:

[1] C. Bernuy-Lopez et al., ECS Transactions, 103 (1), (2021).
Highly Active Layered Cobaltite Air-Electrode Materials for Reversible Solid Oxide Cells
Authors: Jo Minkyeong , Hamayun Muhammad Asif , Park Jun-Young 
Published: September 2023

The use of fossil fuels, which have increased rapidly since the Industrial Revolution, is causing serious climate change. To overcome this, interest in clean and sustainable energy sources to replace fossil fuels is increasing worldwide. Among alternative energies, the electricity generation from solar and wind resources is difficult to achieve sustainable energy production regardless of the weather and season. Hence, hydrogen is considered as the most promising energy source to replace fossil fuels because of its clean, storable, sustainable, and transportable characteristics.
Recently, reversible fuel cells that can both produce hydrogen with surplus power and generate electricity using the stored hydrogen have attracting attentions as an electrochemical device to promote reliable and economical hydrogen society [1]. Among them, reversible solid oxide cells show high efficiency in a fuel cell mode due to their high operating temperature (700-1000 ℃). However, reversible solid oxide cells exhibit relatively low performance in water-electrolysis cell mode [2]. The main reason of low performance in the solid oxide electrolysis cell mode is the sluggish kinetics of oxygen evolution reactions in air-electrode. Therefore, the electrolysis performance of reversible solid oxide cells can be greatly improved if the air-electrode with high catalytic activity for oxygen evolution reactions is developed.
Among many candidate materials for air-electrodes, cobalt-based layered materials are known to have good electrocatalytic properties in oxygen reduction and oxygen evolution reactions with high electronic conductivity (σ = 100–240 S·cm-1 at 450–650 °C) [3, 4]. Herein, we introduce a novel layered structure material, Ba2Co9O14 (BCO), as air-electrode materials for highly efficient and durable reversible solid oxide cells. In order to further enhance the catalytic property of BCO, Nd and Ca are doped into Ba-site. The Nd0.1Ca0.1Ba1.8Co9O14-cell shows a maximum power density of 2.6 W·cm-2 in fuel cell mode, current density of –4.36 A/cm2 under applied voltage of 1.6 V in electrolysis cell mode, at 800 ℃, surpassing previous reported results of air-electrode catalysts for reversible solid oxide cells.

References

[1] S. E. Hosseini, M. A. Wahid, Renew. Sustain. Energy Rev. 2016, 57, 850.
[2] X. Zhang, L. Liu, Z. Zhao, B. Tu, D. Ou, D. Cui, X. Wei, X. Chen, M. Cheng, Nano Lett. 2015, 15, 1703.
[3] M. Saqib, I. -G. Choi, H. Bae, K. Park, J. -S. Shin, Y. -D. Kim, J. -I. Lee, M. Jo, Y. -C. Kim, K. -S. Lee, S. -J. Song, E. D. Wachsman, J. -Y. Park, Energy Environ. Sci. 2021, 14, 2472.
[4] A. Rolle, N. Preux, G. Ehora, O. Mentré, S. Daviero-Minaud, Solid State Ionics 2011, 184, 31.
Study of the Crystallization in a Glass-Ceramic Seal
Authors: Laplace Annabelle , Begos Jean-Gabriel , Vallat Charlène , Regnier Elise , Moles Rémi , Brackx Emmanuelle , Schintu Lilou , Vulliez Karl 
Published: September 2023

Sealing is a major issue in high temperature electrolyzers used for hydrogen production. The specifications that seals must meet are particularly demanding. In addition to sealing, the material must have mechanical, thermomechanical and chemical properties, as well as sufficient electrical resistivity. The geometries are complex and the lengths to be sealed are important. These numerous constraints lead to the use of glass powder suspended in organic solvents. This process allows for the installation of the seal by simply depositing the suspension on the areas to be sealed. A heat treatment is then applied to shape the material and ensure the sealing of the system. The use of a composition that tends to crystallize allows, a priori, improving the thermal and mechanical properties.
The reference heat treatment consists of a first temperature rise followed by a crystallization stage. As the temperature rises, the organic solvents evaporate, producing CO2, which causes porosity to appear. Sintering of the glass powder also takes place during this stage. Early surface crystallization can compete with the sintering phenomenon and prevent the maximum densification of the glass ceramic by freezing the structure. The objective of the study is to obtain a seal material with maximum density, thus minimum porosity, by controlling the removal of organic solvents, sintering and crystallization.
This paper will present in particular the study of the material crystallization: phases identification and evolution of crystal morphology as a function of temperature (SEM, XRD) (Figure 1), crystal surface fraction as a function of time and temperature (determined by image analysis). A poikilitic texture phenomenon, particularly important for the crystalline fraction quantification, is also detailed (SEM-EBSD). These data allow to obtain the equilibrium crystalline fraction as a function of temperature, and to further optimize the thermal treatment.

Figure 1
Perovskite-Type Nd1-XBaxCo0.8Fe0.2O3-δ (0 ≤ x ≤ 0.7) Cathodes for Intermediate Temperature Solid Oxide Fuel Cells
Authors: Sikstrom Daniel , Javed Aroosa , Shoaib Muhammad , Thangadurai Venkataraman 
Published: September 2023

Perovskite-type metal oxides with a nominal chemical formula of Nd1-xBaxCo0.8Fe0.2O3-δ (NBCF) (0 ≤ x ≤ 0.7)
were prepared by solid-state synthesis method at 1300 °C in air. Powder X-ray diffraction showed that the x =
0.25 member is a single-phase perovskite-type Nd0.75Ba0.25Co0.8Fe0.2O3-δ in the Pnma space group and all other
members were found to be multiphase. All the investigated NBCF compositions show minor reactivity with the
Sr and Mg-co-doped lanthanum gallate (LSGM) when sintered with 30 wt.% LSGM at 1050 °C but maintain
their perovskite-type structure. 4-probe DC chronopotentiometry measurements were performed on the sintered
sample pellets. The x = 0.4 member reaches a maximum conductivity of 1068 S/cm at 300 °C in air. Among the
samples studied, the x = 0.55 member exhibits the lowest area specific polarization resistance (ASR) of 0.026 Ω
cm2 at 750 °C in air.
(Digital Presentation) Prolonged Operation Strategies For Solid Oxide Fuel Cell Through Barrier Layer-Based Interface Engineering
Authors: Lyu Qiuqiu , Zhu Tenglong , Qu Hongxia , Zhong Qin 
Published: September 2023

As one of the current benchmark cathode materials, La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) is in the process of widely commercialization. Normally, a high-density barrier layer, such as doped Ceria (Gd0.1Ce0.9O2-δ, GDC), is essentially introduced in SOFC single cell between Zirconia electrolyte and cathode, in order to prevent chemical incompatibility and elements diffusion. However, in large-scale fabrication, the GDC barrier layer is typically screen-printed onto the as-sintered YSZ electrolyte. Consequently, the post-sintered GDC layer is often porous. Increase GDC barrier layer density can effectively facilitate oxygen ions transfer and inhibit elements diffusion. Therefore, in this study, four YSZ electrolyte supported symmetrical cathode cells with various barrier layers are investigated, i.e. (1) screen printed GDC (named as GDC), (2) screen printed GDC with Cobalt Nitrate sintering aid (GDC-Co), as well as hydrothermal modified cells named as (3) GDC-HY and (4) GDC-Co-HY, respectively. The results show largely decreased Rohm of ~20% when sintering aid are used in GDC barrier layer. Furthermore, both Rohm and Rp values are extremely stable after further hydrothermal modification, with growth rate of 0.014 and 0.03 Ω·cm2/kh for GDC-Co-HY, respectively, which are much lower than 0.22 and 0.248 Ω·cm2/kh for pristine GDC-Co. Current study suggests that increasing the GDC barrier layer density by hydrothermal modification is an effective method to enable better cell performance and more stable long-term operation.
Figure 1 Evolution of (a) Rohm and (b) Rp with aging time in air. Microstructure of the GDC surfaces (c-f) and cell fractures (g-j).

Figure 1
(Digital Presentation) GDC/YSZ Bilayer Electrolyte Fabrication by In-situ Hydrothermal Growth
Authors: He Jianyu , Lyu Qiuqiu , Zhu Tenglong , Zhong Qin 
Published: September 2023

GDC (gadolinia-doped ceria) can be used as barrier layer between the high-performance LSCF (La0.6Sr0.4Co0.2Fe0.8O3-δ) cathode and YSZ (8% mol yttria stabilized zirconia) electrolyte, to prevent chemical incompatibility and elements diffusion. However, the GDC layer is difficult to achieve as high density as the YSZ electrolyte, especially under low sintering temperatures. While, increase sintering temperature over ~1200 ℃ could induce the formation of (Ce,Zr)O2 solid solution.
In this work, we report a highly dense bilayer GDC/YSZ electrolyte prepared at low sintering temperature. Specifically, the as-sintered anode supported SOFC half-cell with already-dense YSZ electrolyte was immersed in solution of Gd(NO3)3·6H2O and Ce(NO3)3·6H2O, followed by a hydrothermal treatment at 180 ℃ (accounts for steam pressure of ~1 MPa) for 36 h. This yielded a dense GDC layer growth on YSZ electrolyte with thickness of ~200 nm. Then, the cells were sintered at 1100, 1150 and 1200 ℃, respectively. Afterwards, the hydrothermal treatment was repeated once, to grow an additional GDC layer. This post-grown GDC was then co-sintered with the screen printed LSCF cathode at 1075 ℃.
Results show that, the GDC/YSZ bilayer electrolyte is successfully fabricated under low sintering temperature below 1200 ℃, with overall GDC layer as thick as ~540 nm and ultra-high density as the YSZ electrolyte. The single cell with 1200 ℃ sintered GDC, named as GDC-1200, shows the best output performance, i.e. maximum power density of ~0.96 W/cm2 at 780 ℃. Moreover, the cell runs stably at 720 ℃ for 300 hours, showing decent durability.
Fig. 1 (a) j-V-P curves of bilayer electrolyte SOFCs with varied GDC sintering temperature; (b) operation voltage versus time for GDC-1200 cell under constant current mode; (c) SEM images and (d) EDS mapping of single cell (GDC-1200) fracture

Figure 1
Investigation of La0.65Ca0.35FeO3−δ
as a Co-Free Cathode for Protonic Ceramic Fuel Cells with Yb-Doped BaZrO3 Electrolyte
Authors: Watanabe Konosuke , Shimada Hiroyuki , Yamaguchi Yuki , Nomura Katsuhiro , Sumi Hirofumi , Kagomiya Isao , Mizutani Yasunobu 
Published: September 2023

In protonic ceramic fuel cells (PCFCs), the use of cobalt-free cathodes is expected to reduce manufacturing costs and improve durability performance. However, cobalt-free cathodes generally tend to have poor power generation performance due to their lower catalytic activity than cobalt-containing cathodes. Therefore, based on a previous study in which higher power generation performance was obtained with SOFCs using La0.65Ca0.35FeO3−δ
(LCaF) than with SOFCs using La0.6Sr0.4Co0.2Fe0.8O3-δ
(LSCF) containing cobalt, we focused on LCaF as a cobalt-free cathode. In this study, we attempted to apply cathodes with LCaF to anode-supported PCFCs using a BaZr0.8Yb0.2O3-δ
(BZYb) electrolyte in order to improve the power generation performance and durability of PCFCs.
The proton-conducting oxides used for composite cathodes were investigated. BZYb, which is the same as the electrolyte, was used, but the adhesion between the electrolyte and the cathode was poor. When, BaZr0.1Ce0.7Y0.1Yb0.1O3-δ
(BZCYYb), which has good sinterability compared with BZYb, was therefore used, reading to improvement in the adhesion. Moreover, process parameters such as composite ratio and sintering temperature were also optimized. As a result, a maximum power density of 0.4 W cm-2 at an operating temperature of 600 °C was obtained for PCFCs using a composite cathode of LCaF and BZCYYb at a weight ratio of 6:4 sintered at 1100 °C, which is equivalent to PCFCs using a cathode with LSCF. In addition, the voltage drop rate of PCFCs using a composite cathode of LCaF and BZCYYb in the constant current durability test (0.26 A cm-2) at an operating temperature of 600 °C was 4% per 1000 hours, less than 1/10 that of PCFCs using a cathode with LSCF. Based on these results, LCaF is one of the candidate materials of cobalt-free cathode for PCFCs.
Acknowledgements: This work is based on the results obtained from a project (JPNP20003) commissioned by the New Energy and Industrial Technology Development Organization (NEDO), Japan.