bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Reliability Analysis of Large Planar Steam Solid Oxide Electrolysis Cells
Authors: Bao Jie , Fitzpatrick James , Karri Naveen , Koeppel Brian , Meinhardt Kerry D , Marina Olga A
Published: September 2023

Solid oxide electrolysis cells (SOEC) have been receiving significant attention recently because of their high energy efficiency and fast hydrogen production. In our previous study, a multi-physics modeling framework to simulate the SOEC performance and structural reliability of planar SOEC design was developed and demonstrated. The electrochemical reactions, fluid dynamics, species transport, electron transfer, and heat transfer were modeled in the commercial computational fluid dynamics (CFD) software STAR-CCM+. The thermomechanical analysis and the associated structural reliability evaluations were conducted using the commercial finite element analysis software ANSYS. The electrochemistry model was validated by using the experimentally obtained current-voltage (I-V) characteristics of the electrode-supported SOECs. In this study, this framework was applied on a large 300 cm2 steam planar SOEC design, and systematically studied the structural reliability under combinations of cell operating conditions, with cell voltage 1-1.5 V, steam fraction in fuel inlet 0.7-0.9, air inlet flow rate 0-10 L/min, fuel inlet flow rate 2.5-12.5 L/min, and inlet temperature 600-900 C. In the modeling framework, all the cells were investigated under the adiabatic thermal conditions, which is equivalent to packing the cell in an insulated container. This induced the relatively larger temperature variation than in the smaller cell designs. This cell internal temperature non-uniformity may further enhance the spatial variations of open circuit voltage, activation loss, and ionic conductivity in the cell, which all influence the overall cell performance. This situation is more obvious when the cell voltage is higher than 1.35V, under which the cell is significantly heated along the steam flow direction. Traditionally, it is assumed that the cell internal temperature spatial variation plays an important role on cell structural reliability. However, because it was assumed that all the components in cell are stress free at 850 , the cell temperature deviation from 850 is more critical to the stress distribution and structural reliability in the cell. For the investigated cells in the practical conditions, like 750 C inlet temperature and varying voltage from 1.05 to 1.5 V, the highest first principal stress is always in the air side electrode, which is around 45 MPa. This is explained by the higher coefficient of thermal expansion of LSCF-GDC with respect to the other layers. This may indicate that the failure would possibly occur in the air side electrode, but at low risk due to the relatively higher Weibull characteristic strength.
Role of Dopants in Fine-Tuning the Electrical and Catalytic Properties of Barium Niobate Perovskites Towards High-Temperature Electrolyzer Application
Authors: Ramaiyan Kannan , Denoyer Luke H , Benavidez Angelica , Garzon Fernando H.
Published: September 2023

Perovskite materials are being studied for high temperature electrochemical applications such as solid oxide fuel cells (SOFC) and electrolyzers due to their tunable conductivity and catalytic activity. However, high temperature operation poses significant challenges in both fabrication and durable operation that is further complicated by the operating environment.1 We studied barium niobates with various dopants such as Fe, Ni, Ca, Y, and Mg for B site doping while Sr, K, and La are studied for A site doping. These niobates showed enhanced chemical stability in SOFC relevant conditions and catalytic activity towards methane activation. Nb4+/5+ redox couple seem to be a key reason behind this chemical stability while the size and electronegativity of the dopants affect the electrical properties.2 Catalyst exsolution is explored with dopants such as Fe, Ni, and Co under reducing conditions along with surface bound metallic nanoparticles prepared by an incipient wet synthesis method. Chemical stability of these perovskites was analyzed by an in situ TGA measurements under various gas environments followed by analysis of the powders using PXRD, XPS, SEM, and TEM methodologies.3 Methane activation properties are further analyzed in a temperature programmed reaction setup while Electrochemical properties were evaluated in a home-made setup using different electrolyte materials in the temperature range of 700°C to 900°C. Cyclic voltammetry, impedance spectroscopy, and chronoamperometry measurements coupled with continuous mass spectra analysis was utilized to diagnose any correlation between product distribution and applied potential. Our results demonstrate doped barium niobates as a promising candidate for stable operation in high temperature electrochemical applications. The presentation will discuss these results and provide a correlation between dopants and catalytic activity and chemical stability of doped barium niobate perovskites.

References

(1) Ramaiyan, K. P.; Denoyer, L. H.; Benavidez, A.; Garzon, F. H. Selective Electrochemical Oxidative Coupling of Methane Mediated by Sr2Fe1.5Mo0.5O6-δ and Its Chemical Stability. Commun. Chem.
2021, 4 (1), 139. https://doi.org/10.1038/s42004-021-00568-1.

(2) Denoyer, L. H.; Benavidez, A.; Garzon, F. H.; Ramaiyan, K. P. Highly Stable Doped Barium Niobate Based Electrocatalysts for Effective Electrochemical Coupling of Methane to Ethylene. Adv. Mater. Interfaces
2022, 9 (27), 2200796. https://doi.org/10.1002/admi.202200796.

(3) Denoyer, L. H.; Benavidez, A.; Garzon, F. H.; Ramaiyan, K. P. Chemical Stability of BaMg0.33Nb0.67-XFexO3-δ in High Temperature Methane Conversion Environments. under communication - ECS Journal of Solid State Science and Technology.
Dependence of Faraday Efficiency on Operation Conditions and Cell Properties for Proton Ceramic Electrolysis Cells
Authors: Zhang Qian , Vera Clarita Y. Regalado , Ding Hanping , Tang Wei , Wu Wei , Barnett Scott A , Voorhees Peter W. , Ding Dong
Published: September 2023

Proton-conducting solid oxide electrolysis cells (p-SOECs) have attracted much attention due to their low operating temperature and low degradation rate compared with conventional oxygen-ion conducting solid oxide electrolysis cells (o-SOEC). However, p-SOECs suffer from relatively low Faradaic efficiency due to the electronic leakage of the electrolyte. Using an electrolyte charge carrier transport model, we quantified the dependence of Faraday efficiency on the electrolysis operation conditions. Our model describes the transport of charge carriers in the electrolyte when the polarization resistance can not be neglected during cell operations. By accounting for the overpotentials at the interface of electrode and electrolyte in the model, we found that the Faraday efficiency decreases with the increasing current densities at electrolysis mode for both BZY20 and BCZYYb. Our results provide significant insights into the development of highly efficient p-SOECs.
Electrochemical Deposition of Nanocatalysts on an Oxide Scaffold Enhances the Activity of Oxygen Reduction
Authors: Nam Seongwoo , Kim Jinwook , Kim Hyunseung , Jeon SungHyun , Ahn Sejong , Choi Yoonseok , Park Beom-Kyeong , Jung WooChul
Published: September 2023

Solid oxide fuel cells (SOFCs) are devices that directly convert the chemical energy of hydrogen and oxygen into electrical energy, and are attracting attention for their high efficiency and eco-friendliness. Since the recent research trend is to lower the operating temperature of the device, there is a considerable demand for a way to effectively introduce a catalyst to overcome the poor electrochemical activity of the most commercially available lanthanum strontium manganite–yttria-stabilized zirconia (LSM-YSZ) composite electrode.

Praseodymium oxide (PrOx) is an excellent catalyst for the ORR and has also been applied to LSM-YSZ electrodes via infiltration, the most widely used catalyst fabrication method. However, this previously well-established method still experiences time-consuming and energy-intensive limitations; therefore, other catalyst fabrication approaches are required.

Cathodic electrochemical deposition (CELD) is chosen as a central strategy to decorate the PrOx catalyst which strongly empowers the exclusive ORR activity of the LSM-YSZ electrode. CELD is an excellent catalyst fabrication method that combines electroplating and chemical precipitation, and is simple, fast, cost-effective, and capable of deposition at room temperature and ambient pressure.

Herein, we present an electrochemical deposition method that fabricating a PrOx overlayer significantly improves the catalytic activity of composite electrodes with only a short process of less than 4 min, even in an ambient environment. Moreover, it does not require additional processes such as heat treatment. The PrOx-coated electrode exhibits a decrease in initial polarization resistance compared to the bare, and maintained an oxygen reduction reaction characteristic by more than 10 times even after about 400 hours of operation at 650 °C. Transmission line model analysis with impedance spectra describes how PrOx improves the reactivity of the oxygen reduction reaction of composite electrodes. Finally, we demonstrate that a two-element material, (Pr, Ce)Ox, was electrochemically deposited. Electrochemical deposition considerably improves the catalytic properties of the cathode via a concise and straightforward process.
Oxidation Process of Ni Cathode in CO2 Electrolysis in SOEC: X-Ray and DFT Study
Authors: Watanabe Hirotatsu , Higashidani Syo , Tawa Aoba , Ban Ikken , Ogura Teppei
Published: September 2023

Solid oxide electrolysis cells (SOECs) can convert H2O and CO2 to syngas(H2/CO) at high temperature, promising a way in the power-to-gas process. A Ni electrode such as nickel/yttria-stabilized zirconia (Ni/YSZ) and nickel/scandia-stabilized zirconia (Ni/ScSZ) have widely used as a cathode for SOECs. Meanwhile, the cathode faced severe oxidizing condition due to a high steam and CO2 content. H2, a reduction agent, can inhibit the cathode oxidation; however, an additional H2 decreases a total energy efficiency. Oxidation tolerance is an important parameter for the material candidate as the cathode. A combination study of X-ray and DFT study is a promising way to understand oxidation mechanisms of Ni cathode, which provides an useful hint in the cathode design with oxidation tolerance.

In this study, oxidation process of Ni cathode in CO2 electrolysis was studied using X-ray and density functional theory (DFT). Ni cathodes (Ni/YSZ, Ni/ScSZ) were used in H2/CO2 environment under the electrolysis mode. After CO2 electrolysis, Ni cathode surface was analyzed using SEM/EDS and X-ray diffraction (XRD). Influence of H2/CO2 ratio and operating condition on cathode oxidization was studied in the electrolysis mode. All calculations here are performed employing the plane wave density functional theory (DFT) method implemented in the Vienna Ab-Initio Simulation Package (VASP).

XRD results showed that the cathode oxidation was progressed at H2/CO2 ratio of 0, whereas the cathode oxidation was inhibited when the H2/CO2 ratio was higher than 0.75 at 800 oC. In addition, it was suggested that the electrolysis mode, in which oxygen was moved from the cathode to the anode, had a role in inhibiting the cathode oxidation. In the DFT calculation, an activation energy of CO2 decomposition at the triple phase boundary (CO2→CO+O,vacancy) was much lower than that at the Ni surface (CO2→CO+O,Ni), indicating that CO2 electrolysis was more preferable than Ni oxidation. It was shown that the electrolysis mode can enhance the oxidation tolerance of Ni cathode. Moreover, Ni/YSZ and Ni/ScSZ cathode were also studied in terms of CO2 electrolysis and oxidation. The activation energy of CO2 decomposition of Ni/ScSZ was lower than that of Ni/YSZ mainly because O can easily enter the vacancy in the ScSZ. It was shown that the oxidation can be controlled from the electrolyte structure in the electrolysis mode.
Advancement of Proton Conducting Solid Oxide Electrolysis Cells (p-SOEC) for Hydrogen Production at Idaho National Laboratory
Authors: Ding Dong
Published: September 2023

Proton Conducting Solid Oxide Electrolysis Cells (p-SOEC) is an emerging and attractive technology for hydrogen production through water electrolysis at intermediate temperatures. Economically competitive p-SOEC systems have distinct advantages over conventional oxygen-ion conducting ceramic electrochemical cells, but further technology development and widespread market acceptance will require continuous innovation of materials and structures in order to improve cell performance, enhance system lifetime and reduce cost. Herein, we report the advancement of p-SOEC with materials R&D, interface engineering, as well as cell fabrication and manufacturing in INL. We highlight how DOE support through HydroGEN accelerates move up the technology readiness level.
Progress of the Evaluation and Analysis Methods for Durability of SOFC Stacks
Authors: Horita Teruhisa
Published: September 2023

Recent progress in the development of R&D for the evaluation and analytical methods of SOFC stack durability is reported under the NEDO Japanese national project. The goal of this project is the following two points: (1) to develop the advanced evaluation and analytical methods for the cell stacks which show a lifetime over 15 years (130 kh) with high efficiency of over 65% LHV, and (2) to develop the evaluation and analytical methods for dynamic operation mode such as rapid start-stop and load cycling. Three practical stacks were supplied by the stack developers and tested over 10,000 hours with high fuel utilization (Uf~85%). Relatively stable performances were reported for these stacks and degradation factors were considered taking into account the degradation mechanisms at cells and stacks. Under high Uf conditions, some specific degradation mechanisms are now analyzed in the cells. For rapid starts of stacks, evaluation protocols are considered taking into account the mechanical stress arising from the thermal distribution in the cells. Simulation methods are considered for the evaluation of performance after 15 years of operation in the stacks.
Electrochemical Performance of Direct Ammonia Solid Oxide Fuel Cell
Authors: Lee Sanghwa , KIM Jooeon , Kim Kyungsun , Hwang Haejin
Published: September 2023

Recently, as regulations on greenhouse gas emissions have been strengthened in various industries such as automobiles and ships, many studies on alternative energy are being conducted. Hydrogen is a good energy carrier and an environmentally benign fuel because the reaction product is only water or water vapor when it is burned or is used for fuel cells. However, hydrogen suffer from its low specific volume, so the storage issue is still remained unsolved.

Ammonia (NH3) has a higher energy density (12.7 MJ/L) than liquid hydrogen (8.5 MJ/L). Liquid hydrogen has to be stored at cryogenic conditions of –253°C, whereas ammonia can be stored at a much less energy-intensive –33°C. In addition, ammonia is much less flammable than hydrogen although it is hazardous to handle.

In this study, anode-supported SOFCs consisting of LSCF-GDC cathode, YSZ electrolyte, and Ni/YSZ cermet anode was fabricated and their electrochemical performances (Impedance spectra, J-V curve and cell voltage degradation with operation time) were investigated at 600, 650, and 700°C under ammonia and hydrogen. Regardless of the operating temperature, the power densities of ammonia-fueled SOFCs were almost similar to those of hydrogen-fueled SOFCs. This suggested that the ammonia cracking reaction effectively occurred in the Ni-YSZ anode support. However, the cell voltage at 0.2 A/cm2 was slightly decreased as a function of operating time, which means that the nickel was degraded under ammonia atmosphere. The change of an anode’s microstructure before and after the degradation test will be discussed. In addition, Ni-YSZ catalysts for ammonia cracking were fabricated and their catalytic activity was measured in terms of operating temperature and space velocity using in-line gas chromatography. The phase evolution and microstructure of catalysts were characterized by XRD, SEM and TEM.
Analysis of the Long-Term Operation of an Electrolyte-supported Solid Oxide Cell Under Co-electrolysis Regime
Authors: Lopez de Moragas Albert , Tsai Chen-Yu , Hauch Anne , Chen Ming
Published: September 2023

Solid oxide technology allows to produce synthesis gas (CO+H2), a relevant mixture and precursor for e-fuels and other products in the chemical industry. This work reports on the long-term performance of an electrolyte supported cell (Ni-CGO/3YSZ/LSCF-CGO), operating at industrially relevant co-electrolysis conditions (32.5 % H2/35 H2O/8.1 CO/24.4 CO2, -0.5 A/cm2, 816 °C). The applied cell had a Ni-CGO fuel electrode (~30 μm thick), a 3YSZ electrolyte (~90 μm) and an LSCF-CGO oxygen electrode (~35 μm thick) including a thin CGO protective layer.

The cell was operated successfully for 2300 h at constant galvanostatic test conditions, with an overall degradation of 80 mΩ cm2/kh, which is a higher degradation rate than the reported for similar cells at comparable conditions. At the start of the test, the ohmic resistance contributes to almost 90 % of the ASR (area-specific resistance), but the increase in Rp (polarization resistance) is what contributes the most to the increase in ASR during the long-term operation.

This increase in ASR is not constant over the entire test time. On the contrary, it is considerably higher during the first 300 hours (180 mΩcm2/kh) and then it falls and stabilizes during the last app. 2 kh of the long-term operation of the cell to 32 mΩcm2/kh. The increase in ohmic resistance is in percentage small but steady at 7 %/kh, while the increase in polarization resistance follows the same trend as the ASR.

Electrochemical impedance spectroscopy (EIS) showed a decrease of the performance of the Ni-CGO fuel electrode. A possible explanation for the observed fuel electrode degradation was found via SEM-EDS, where a considerable quantity of silicon-containing species was found in the active area of the Ni-CGO fuel electrode.
Shape-Controlled Ni Supported GDC Catalyst and its Application in Direct Ethanol Solid Oxide Fuel Cells
Authors: Machado Marina , Rodrigues Lays Nunes , Vilela Vanessa Bezerra , Ferlauto Andre Santarosa , Moraes Tamara , Fonseca Fabio Coral
Published: September 2023

Matching catalytic activity with the high temperature heat treatments required to process solid oxide fuel cells (SOFCs) can be a challenge. Shape control is an interesting strategy to stabilize the surface of nanoparticles during heat treatments. In this study, nickel-based catalysts supported on shape-controlled (nanorods and nanocubes) gadolinium-doped cerium oxide (GDC) were evaluated for direct ethanol SOFCs. The morphology of the support had a significant effect on the catalytic activity. It was shown that the Ni catalyst supported on the GDC nanorods maintained high catalytic activity after heat treatments for catalytic layer sintering. Such catalyst was applied as catalytic layer on a SOFC operating directly on anhydrous ethanol at 700 °C. The fuel cell operated for more than 100 h under 0.6 V displaying consistent performance with no indication of degradation from carbon deposition.
Direct Utilization of Pure and Denatured Ethanol in Metal Supported Solid Oxide Fuel Cells
Authors: Hu Boxun , Tucker Mike C
Published: September 2023

Metal supported solid oxide fuel cells (MS-SOFC) are integrated with high entropy alloy reforming catalyst for direct internal reforming utilization of pure ethanol, methanol, and denatured ethanol to generate electricity. Internal reforming SOFCs have advantages over the external reforming SOFCs in terms of cost, energy efficiency, and space-saving. Performance and durability with denatured ethanol, mimicking the compositions of widely commercially-available bio-ethanol, varies dramatically with the composition of the denaturant. This evaluation of bio-ethanol fuel for SOFC application extends beyond the previous literature focusing on high-purity ethanol. Mitigation of carbon deposition is critical to extend the lifetime of MS-SOFCs operating with ethanol. Conventional Ni catalyst shows rapid carbon deposition, and in contrast the HEA catalyst has excellent resistance to carbon deposition. The HEA also enables complete internal reforming without localized cooling, resulting in high power density >0.8 W/cm2 at 700°C. Long-term operation (500-1000 hours) at the operating temperature of 600-800°C will be presented. Various strategies are applied to improve the cell stability. The effect of impurities and fuel compositions on the cell performance and stability is evaluated. Other degradation factors such as Cr evaporation and catalyst agglomeration are analyzed by SEM-EDS and EIS. It is found that MS-SOFCs are promising for direct utilization of bio-ethanol, offering a path to rapid-start, carbon-neutral operation.
Evaluation of Electrolytic Characteristics with a Single Cell Developed as SOFC
Authors: Imabayashi Takumi , Asano Koichi , Mugikura Yoshihiro
Published: September 2023

In recent years, it is concerned that a power supply and demand balance of power grid become unstable because of large introduction of variable renewable energy such as solar photovoltaic power generation. The reversible solid oxide cell (rSOC) can operate both SOFC and SOEC modes reversibly. Therefore, the rSOC can be used as a flexibility device for the power supply and demand adjustment by operating reversibly in response to power grid balance.

Furthermore, CO2 electrolysis and co-electrolysis, which can generate synthesis gases such as H2 and CO, which are raw gases for methane or liquid fuels, from CO2 and H2O by adding an electric power, are promising carbon recycling technologies.

In this study, the electrolytic characteristics were evaluated with a single cell developed as SOFC. It was confirmed in CO2 electrolysis test that CO2 can be directly electrolyzed to CO with about 100% current efficiency. In addition, the electrolysis voltages were clarified under various gas conditions in co-electrolysis and the cell performance factors were analyzed by our original method. In this method, the cell performance factors can be described by the internal resistance loss (IR loss, measured value), the fuel electrode overvoltage, the oxygen electrode overvoltage, and the Nernst loss (calculate value). As a result of this analysis in co-electrolysis mode before and after all tests, it was shown that the increase in IR loss was the main factor of the decrease in cell performance.
Durability Study of Anode-Supported SOFC with Large-Area Fabricated By 4-Layer Sequential Co-Lamination and GDC Co-Firing Process
Authors: Hussain Amjad , Song Rak-Hyun , KIM Taehun , Mehdi Ali Muqaddas , Shin Ji-weon , Kwon Beom-Su , Ali Muhammad Measam , Joh Dong Woo , Khan Muhammad Zubair , Hong Jong-Eun , Lee Seungbok , Lim Tak-Hyoung
Published: September 2023

Electrolyte-Cathode interfaces are life-threatening regions of solid oxide fuel cells where degradation phenomena occur due to chemical interdiffusion. The Buffer layer is inserted between electrolyte-cathode to limit the cation exchange across the interface. However, state of art buffer layer coated by screen printing does not fully prevent cation migration which results in the formation of insulating phases such as SrZrO3. Herein, a reliable four-layered (NiO-YSZ, NiO-CeScSZ, CeScSZ, and GDC) thin film-based anode supported SOFCs with a large-area (12cm×12cm) were fabricated by sequential co-lamination, in which all cell components perform a distinct role to enhance the interfacial connectivity and packing density of electrolytes. This enhanced connectivity with a highly dense electrolyte (5-6µm) and buffer layer (2-3 µm) accomplished on the porous anode support without any structural defects. The single cell (144cm2) showed a power output of 38W at total current 50A (700°C). The Post-tested cell had exceptional micro-structural characteristics, excellent interfacial adhesion and retained its structural integrity during static and dynamic operation. Also, the formation of insulating phases and decomposition of cathode was effectively prevented, resulting in a remarkable improvement in durability. The cell with four-layered structure exhibits an extreme low-degradation rate of 0.2% kh-1 under 25A current and 21 dynamic load cycling conditions, which satisfies the strict benchmark of durability for commercialization of technology.

Key word: Durability, interfacial connectivity, insulating phase, sequential co-lamination

Figure 1
Interface Resistance Analysis in Solid Oxide Fuel Cells
Authors: Yoo Hyun Sik , Megra Yonas , Suk Ji Won , Lee Wonyoung
Published: September 2023

A sophisticated design of the interface structure between the cathode and the electrolyte is essential to improve the performance of solid oxide fuel cells (SOFCs). It is because the interface is the place where it directly affects both the ohmic resistance and the polarization resistance as interface contact and interface reaction, respectively. To improve interface properties, electrolyte surface treatment or inserting interface functional layer between the cathode and the electrolyte have been applied. They improved cell performance by effectively enhancing the interfacial characteristics such as interface bonding and interface reaction area. However, although both ohmic and polarization resistance greatly contributed to the improved cell performance, a detailed analysis related to ohmic resistance compared to polarization resistance is insufficient. Unlike polarization resistance which can quantify interface reaction related resistance using distribution of relaxation time (DRT) model, there is no proper methodology to quantify interface resistance in the case of ohmic resistance. The interface resistance has been analyzed to the extent that it belongs to the remaining resistance except for the electrolyte resistance from total ohmic resistance in consideration of the ionic conductivity and thickness of the electrolyte, which still not completely separate the interface resistance from the total ohmic resistance. Furthermore, in recent years, the electrolyte thickness has gradually decreased to less than 5 μm for high-performance and the electrolyte resistance has been significantly reduced, increasing proportion of interface resistance in total ohmic resistance. Therefore, we need to reduce the interface resistance for further cell improvement. Also, quantifying the interface resistance and having a deeper understanding of the correlation between interface resistance and interface structure should be supported.

Here, to realize the interface resistance from the ohmic resistance, we designed several types of interface structure using electrostatic spray deposition (ESD) which can precisely control the particle size and be used to fabricate a thin functional layer. Using the different interface properties and equivalent circuit models, we separate the interface resistance from the ohmic resistance quantitatively. Our results can suggest a simple and effective interface analysis method for achieving high performance SOFCs.

Figure 1
Solid Oxide Stack Development at Elcogen
Authors: Noponen Matti , Puranen Jouni , Alfano Antonio , Granö-Fabritius Hanna
Published: September 2023

Elcogen is one of the leading European manufacturers of solid oxide cell (SOC) and stack technologies. Elcogen stacks are a unique combination of best-in-class performance and low-cost product structure. The stack products are designed for low temperature operation enabling major cost reductions on the system level. This article summarizes the recent activities and development trends of Elcogen.

Elcogen solid oxide technology can be used both in electrolysis and fuel cell mode. In electrolysis mode, steam is converted with electricity into green hydrogen. The electrolysis technology can also be used to produce syngases for e-fuel production by combining steam and carbon dioxide. Elcogen technology can be operated at high conversion efficiency level with a variety of fuels in the fuel cell mode.

Elcogen is currently focused on ramping up its unit cell and stack production with increased customer demand. The goal is to set-up of a manufacturing plant for stacks with annual capacity close to 200 MW in electrolysis mode.
Investigation of Surface Oxide Layer Structure to Improve Durability of Stainless Steels Under Humidified Hydrogen
Authors: Taniguchi Shunsuke , Inoue Yuko , Uryu Chie , Pham Hung Cuong , Chou Jyh-Tyng , Sasaki Kazunari
Published: September 2023

We study degradation mechanism of stainless steels under SOFC operating conditions to improve durability of SOFC stack. To reduce material cost, a low-cost stainless steel is preferred because metal interconnect occupies considerable amount in the stack. From commercially available stainless steels, four types of alloy composition were chosen as model materials, which are widely used in the other applications.

The alloy test pieces were exposed to hydrogen with 10%-50% H2O at 600oC-700oC, and mass gain after the test was measured. The mass gain increased with time, indicating that steam oxidation proceeded. The oxidation rate was smaller for JIS SUS430J1L than the other three types of the alloy for all the test conditions. The proficient durability came mainly from the thin Cr-rich oxide layer covering the alloy uniformly with little defect or segregation. The additives in the alloy such as Nb also may have an effect on suppressing elemental diffusion through the oxide layer.

Because morphology of the surface oxide layer initially formed on the surface should affect the process of steam oxidation during SOFC operation, we investigated influence of pre-heat treatment condition (700oC-900oC) of the alloy. The surface oxide layer formed by the pre-heat treatment at 900oC in air for 2 h had an effect of reducing steam oxidation rate. Microstructure of the surface oxide layer before and after the durability test was analyzed by STEM. From the difference in the microstructure of the surface oxide layer, predominant factor to improve durability will be discussed.

This paper is based on results obtained from a project, (JPNP20003), commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

Figure 1
Understanding the Physical Properties of Pr-Gd Co-Doped Ceria and Its Role As the Interlayer in Solid Oxide Cells
Authors: Adjah-Tetteh Christabel , Wang Yudong , Niaz Atif Khan , Jia Zhiyong , Zhou Xiao-Dong
Published: September 2023

In solid oxide cells, a doped ceria interlayer is widely applied between the state-of-the-art yttrium-stabilized zirconia electrolyte and the oxygen electrode to mitigate thermal expansion mismatch and chemical interactions for extended durability. The conventional gadolinium doped ceria is usually a pure ionic conductor and blocks electronic currents under oxidative atmosphere. Adding electronic conduction to the interlayer may increase triple phase boundary areas, thus decrease charge transfer resistance and improve electrode stability. The addition of Pr in Gd-doped ceria results in unique physical properties such as an oxygen partial pressure (pO2) dependent ionic conductivity and electronic conduction in a wide range of pO2. In this study, Pr/Gd co-doped ceria (PGCO) is prepared with varying doping levels and its physical properties such as ionic and electronic conductivities are measured under different oxygen partial pressures and temperatures. PGCO with varying Pr/Gd doping is investigated as interlayer for solid oxide cell applications.
Solid Oxide Fuel Cells for Aviation
Authors: Nehter Pedro , Geisler Helge , Ahilan Vignesh , Friedl Stephan , Rohr Oliver , Walter Aurelie , Metzner Christian , Zimmermann Kristian
Published: September 2023

Airbus has revealed ZEROe, three concepts for the world’s first zero-emission commercial aircraft which could be brought to market by 2035. The ZEROe concept aircrafts, which support Airbus’ commitment to lead the decarbonisation of the aviation industry, all rely on hydrogen as a primary power source, which would be deployed via a hybrid-hydrogen configuration featuring modified gas-turbine engines complemented by fuel cells for electrical power. Although the Proton Exchange Membrane (PEM) technology is one of the most matured fuel cell types, Airbus Central Research and Technology (CRT) is also investigating novel SOFC concepts for potential hybrid-hydrogen configurations.

The Solid Oxide Fuel Cell (SOFC) offers major benefits, namely electrical efficiency and fuel versatility, for hybrid-electric aircraft propulsion. Although the SOFC’s area specific power density has drastically increased within the last decade, more needs to be done to make the technology accessible for aviation applications. The combined development of novel SOFC concepts and corresponding manufacturing processes are regarded as key objectives for the SOFC activities at Airbus Central Research and Technology. Airbus is designing, manufacturing and testing SOFC concepts with the aim to achieve highest gravimetric power densities.

Novel manufacturing technologies for metallic and ceramic materials have the potential to enable lighter functional layers for SOFCs with increased intrinsic mechanical stability and surface area. Different cell concepts with an optimized current collection are currently under development at Airbus. The micro-tubular and monolithic SOFC are seen as the most promising concepts, whereas around 2 kW/kg on a cell level has recently been achieved in a performance test at Airbus.
Multi-Flanges for Intensive Cell Development and Lct Forlarge Cell and Stack Evaluation
Authors: Ihringer Raphael , Girardon Jean , Coquoz Pierre
Published: September 2023

Two new test benches have been developed at Fiaxell. One is the multi-Flanges allowing to test 4

cells in one run. All the functionalities of the Open flanges, such as integrated steamer, real or ideal

condition testing, ceramic housing on air side, gas processing are kept apart short stacking.

The second test rig is the LCT for Large Cell Tester. It has been designed for cell dimension

starting from 90 X 90 mm and ending with the size of 130 mm X 170 mm. Again all the Open

Flanges functionalities are kept. The LCT is no delivered for short stack of maximum 3 cells. In the

second part of 2022, heat exchanger made with proper material will be ready for market. It will

allows to test up to 30 cells.

Figure 1
Investigation of the Electrode-Electrolyte Interfaces in Solid Oxide Cells
Authors: Lenser Christian , Schwiers Alexander , Ramler Denise , Menzler Norbert H.
Published: September 2023

The interfaces between electrodes and electrolyte are critical locations in a solid oxide cell (SOC). These interfaces originate from the chemical interaction of two different materials during processing, and are therefore very sensitive to the chemical nature of the materials, as well as the thermal history of the cell. On the air side, perovskite air electrodes tend to form insulating zirconates when sintered on stabilized zirconia, the most common electrolyte material. On the fuel side, using an ionic conductor with a different chemical composition as zirconia can lead to pronounced interdiffusion and the formation of new phases.

Interlayers of doped ceria are frequently used in order to suppress these undesired chemical reactions between electrodes and stabilized zirconia electrolytes. Prior investigations have focused extensively on the chemical composition of the interface and its consequences for cell performance. The focus of this contribution is the microstructure of the interface, as well as the microstructural development during processing.

On the fuel side, the interdiffusion of ceria and zirconia is known to lead to an intermixed phase with decreased conductivity. However, the reduced cell performance of anode-supported cells with Ni-GDC electrodes cannot be explained by an increase in the electrolyte resistance alone. We show that the formation of porosity due to a difference in the diffusion coefficients of ceria and zirconia leads to an increase in the fuel electrode polarization, and investigate possible countermeasures. It is shown that specifically the presence of NiO leads to the formation of porosity at the interface.

On the air side, we investigate the role of a dense interdiffusion layer between ceria and zirconia on the air electrode polarization. We confirm that only a dense interdiffusion layer is necessary by using Pr-doped ceria as a barrier layer, which delaminates after sintering and leaves behind a submicron barrier layer. Finally, we investigate the hypothesis that the densification of the barrier layer during air electrode sintering is essential for electrode adhesion and performance.
On Electrochemically Driven Phase Change and Accelerated Test Protocols in Solid Oxide Cells
Authors: Zhou Xiao-Dong , Wang Yudong , Dogdibegovic Emir
Published: September 2023

The aim of this talk is to address three fundamental questions in solid oxide fuel cells and solid oxide electrolysis cells:

(1) Whether or not the oxygen reduction reaction is indeed the limiting step in solid oxide cells and how to quantify it definitely?

(2) What is the origin for the so-called “electrochemically driven phase transformation and how to translate the understanding to achieve a high-performance and highly stable electrode?

(3) How to develop reliable accelerated test protocols and what’s the physical process that was accelerated?

Quantifying electrode polarization in fuel cells and electrolyzers is of significant importance. It, however, remains difficult because of the substantial overlap of polarizations from both negative and positives electrodes either in a dc or an ac measurement. This challenge leads to a compelling gap in our scientific understanding of electrode phenomena and designing high-performance and durable electrochemical devices. In this talk, we will describe a reproducible method to quantify the polarization of an individual electrode of a solid oxide cell. This method is generic and can be applied readily to other electrochemical cells.

We will then address the greater phase transformation of an oxygen electrode during operation when compared to thermally annealed powders. Theoretical analysis suggests that the presence of a reduced oxygen partial pressure at the interface between the oxygen electrode and the electrolyte is the origin for the phase change in an oxygen electrode. Guided by the theory, an addition of the electronic conduction in the interface layer leads to the significant suppression of phase change, while improving cell performance and performance stability.

Reliable accelerated test protocols are needed for solid oxide fuel cell research to facilitate rapid learning on key durability issues, identify potential modes of failure expeditiously, and eventually predict the calendar lifetime of an electrochemical cell. In this work, solid oxide fuel cells operated at a constant current density were compared to cells undergoing accelerated measurements, which are composed of intermittent current injection to the cell. A general accelerated test profile was developed by cycling a solid oxide fuel cell from open circuit to a predetermined operating current density that is the same as the current density during a steady-state operation, to accelerate the local redox environment. Up to 1,320,000 cycles were generated in this work. The cell degradation was accelerated by nearly 10×, suggesting the feasibility of using this protocol for acceleration test to predict life performance of solid oxide fuel cells.

Finally, we will present a theoretical model that underlies those three questions and can be used to address stability and durability issues in solid oxide fuel cells and solid oxide electrolysis cells.
Durability and Interfacial Elemental Diffusion about BZYb based Protonic Ceramic Fuel Cell
Authors: Mikami Yuichi , Yamauchi Kosuke , Kuroha Tomohiro , Shimada Hiroyuki , Mizutani Yasunobu , Matsuda Ryuma , Mori Masashi , Okuyama Yuji
Published: September 2023

Protonic ceramic fuel cells (PCFCs) are expected to be a highly efficient next-generation fuel cell because the fuel is not diluted by the generated water vapor during power generation. In the past research, we have found that Yb-doped BaZrO3 (BZYb) is promising in terms of the durability against CO2, proton conductivity, and less reactivity with NiO used for the fuel electrode. We are currently developing improvement of power generation efficiency and durability of PCFCs using BZYb electrolyte.

In terms of the durability of PCFCs, there is concern about degradation due to diffusion of transition metals such as Co and Ni used in the air and fuel electrodes. In this study, we evaluated the durability of PCFCs using BZYb electrolyte focusing on the diffusion of transition metals derived from electrodes. We also examined the effect of a buffer layer on the air electrode side.

In this study, fuel electrode supported cells with BaZr0.8Yb0.2O3-δ(BZYb20) electrolyte and NiO-BZYb20 fuel electrode was used. The fuel electrode half cells were fabricated by integrally firing process of the laminated green sheets of the electrolyte and fuel electrode to densify the electrolyte. For air electrode, BaZr0.375Yb0.125Co0.50O3-δ was screen printed on the fuel electrode half cell and fired at 900°C. For the cell with buffer layer between the air electrode and the electrolyte, BaCe0.7Zr0.1Y0.1Yb0.1O3-
δ was spin-coated on the half-cell and then fired at 1300°C. The air electrode was then prepared in the same way. Durability tests were conducted at constant-current mode at 600°C, and the elemental diffusion state of the cells before/after the test was observed by cross-sectional EPMA.

During 1000h power generation, the increase of ohmic resistance and polarization resistance was observed, and the increase in resistance was found to be smaller in cells with buffer layer. The results of cross-sectional EPMA analysis after the power generation test showed differences in the segregation state of Co and Ni in the electrolyte, with a tendency for segregation to be suppressed in the presence of a buffer layer.

Acknowledgement: This work is partially based on results obtained from a project (JPNP20003), commissioned by the New Energy and Industrial Technology Development Organization (NEDO) of Japan.
Solid Oxide Iron-Air Battery for Long-Duration Energy Storage: A Study on Reduction Kinetics of Energy Storage Material Fe-ZrO2 Catalyzed by Ir Particles
Authors: Morey Chaitali , Tang Qiming , Huang Kevin
Published: September 2023

Long duration electricity storage (LDES) with 10+ hour cycle duration is an economically competitive option to accelerate the penetration of renewable energy into the utility market. Unfortunately, none of the available energy storage technologies can meet the LDES’ requirements for duration and cost. The benchmark Li-ion technology can only store and discharge up to 4-hour energy, beyond which it would be cost prohibitive. In this presentation, a new solid-oxide iron-air batteries (SOIABs) with energy-dense solid iron as the energy storage material is shown to have inherent advantages for LDES applications. The presentation will start with the working principle of the SOIAB, baseline performance and bottlenecks of this new technology. It will then show that with a small amount of IrO2 (or Ir during operation) catalyst added into the energy store “Fe-bed”, a lab-size (f1′′) SOIAB can achieve an energy density of 625 Wh/kg, 12.5-hour cycle duration and 90% of round-trip efficiency under LDES-related working conditions. Given the excellent low-rate performance and the use of earth-abundant, low-cost Fe as the energy storage material, we finally conclude that SOIAB is a well-suited battery technology for LDES applications.
Defect Engineering inside Electrolyte for Rapid Proton Conduction
Authors: Kim Donguk , Choi Mingi , Lee Tae Kyeong , Lee Jaeyeob , Lee Wonyoung
Published: September 2023

Proton conducting fuel cells (PCFCs) are promising energy conversion devices that are expected to perform better at lower temperatures than conventional solid oxide fuel cells (SOFCs) because they have higher ionic conductivity and lower activation energy than SOFCs below 600℃. In particular, the ionic conductivity at 500°C of BaZr0.4Ce0.4Y0.1Yb0.1O3-
δ, one of the most promising electrolyte materials among proton conductors, is same to that of Y0.08Zr0.92O2-
δ, the most used electrolyte material among oxygen conductors at 700℃. However, below 500℃, which is the target temperature of the PCFCs, the cathode resistance is much larger than the electrolyte resistance, so the expected performance is not achieved. In this work, we propose an electrolyte structure that can significantly lower the interfacial resistance between cathode and electrolyte by accelerating proton supply to cathode. Concentration gradient of defects is generated inside the electrolyte with a perovskite structure due to the difference in the gas environment between the cathode and anode. In conventional PCFCs, this does not have a significant effect on the ion conduction inside the electrolyte. However, the electrolyte structure, which we proposed, could control the defect concentration gradient inside the electrolyte, and this can eventually generate the steeper proton defect concentration gradient into the cathode than conventional PCFCs. As a result, rapid proton supply to cathode is possible. Through the defect engineering, it is possible to achieve a maximum power density of 0.9 W/cm2 and an electrode resistance of 0.8 ohm cm2 at 500℃.

Figure 1
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).