bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Active Layer Thickness of Reversible Solid Oxide Cells on the Electrochemical Performance of Water Electrolysis
Authors: Kukk Freddy , Pylypko Sergii , Lust Enn , Nurk Gunnar
Published: July 2021

Reversible solid oxide cell technology (RSOC) is a potential method for stabilizing intermittent green power sources. RSOC can act as a solid oxide fuel cell (SOFC) or as a solid oxide electrolysis cell (SOEC). Development of SOFCs has been in focus for decades but SOEC systems have received much less attention by researchers. In this work commercial solid oxide cells (SOC) with modified hydrogen electrode active layers have been studied in SOEC mode at various operating conditions to determine the effect of the active layer thickness on the performance of the SOC in SOEC mode. Commercial SOCs with different hydrogen electrode active layer thicknesses (0, 7, 12, 16, and 20 µm) were characterized electrochemically and fitted via the complex non-linear least squares fitting method. The best performances were achieved for SOEC with the 7, 12, and 16 µm active layer thicknesses depending on the operating conditions applied. The maximum current density measured for the cell with a 7 µm thick active layer at 800°C and at 90% water vapor content was ~3.5 A/cm2 at 1.4 V.
Use Co- and Ni-Free Air Electrode in Solid Oxide Cell Manufacturing for Electrolysis and Fuel Cell Applications
Authors: Ferchaud Claire Julie , Berkel Frans , Berkeveld Loek , Heijink-Smith Miranda , Veldhuis Jakobert , van Wees Hans
Published: July 2021

Reduction of critical raw materials in the manufacturing of Solid Oxide Cell (SOC) is a key requirement to achieve low cost and large-scale commercialization of high-temperature electrolysis and fuel cell systems. A novel air electrode architecture based on Co- and Ni-free materials with the (La,Ca,Sr)FeO3-δ perovskite class of materials is currently under development at TNO within the European project NewSOC. The typically increased overpotential of Co- and Ni-free air electrodes is a challenge, which is aimed to be tackled by introduction of a patterned porous barrier layer and addition of a composite layer at the electrode/electrolyte interface in order to enhance the triple phase boundary density of the air electrode. A highlight of this ongoing research in presented in this paper.
Enhanced Gas Diffusion in Reversible Solid Oxide Cell Fabricated by Phase-Inversion Tape Casting
Authors: Kishimoto Masashi , Higuchi Kazuhiro , Seo Haewon , Masuyama Asuto , Iwai Hiroshi , Yoshida Hideo
Published: July 2021

A hydrogen-electrode-supported solid oxide cell (SOC) is fabricated by phase-inversion tape casting technique and its electrochemical performance is investigated with particular focus on high fuel utilization operation and reversible operation. Structure of the hydrogen-electrode support layer is also analyzed. Electrochemical performance of the cell is measured and compared with that obtained from a conventional cell having homogenous porous structure in the hydrogen electrode support. Equivalent circuit fitting analysis is performed for quantitative understanding of impedance spectra. The results indicate that the finger-like pores in the hydrogen-support layer introduced by the phase-inversion process can significantly enhance gas diffusion property of the layer and hence improve cell performance particularly at lower reactant concentrations. Also, asymmetry in cell performance between fuel cell and electrolysis cell modes is suppressed, which is desirable for reversible operation of SOCs.
Production of Carbon Neutral Methanol Using Co-Electrolysis of CO2 and Steam in Solid Oxide Electrolysis Cell in Tandem with Direct Air Capture
Authors: Ferguson Katelyn M , Saafan Hussein , Wildeboer Emma K , Reeves Troy , Croiset Eric
Published: July 2021

The increasing concentration of carbon dioxide (CO2) in the atmosphere since the industrial revolution is a major contributor to climate change. Among the several options to tackle this issue, the removal of CO2 from the atmosphere and its subsequent use is becoming increasingly attractive. This paper presents a techno-economic feasibility study and quantification of the environmental benefits of combining direct air capture (i.e. capturing CO2 from the atmosphere) with co-electrolysis of water and the captured CO2 in a solid oxide electrolyser cell (SOEC). It was found that the fuel methanol could be modelled to be produced in a carbon negative manner but is not profitable due to current SOEC capital cost. The capital cost of the SOEC is expected to be cut in half by 2030. This would allow for profitable production of methanol.
Characterization of Ag-Based Filler for Electrolyte/Metallic-Interconnect Joint in Metal-Supported Solid Oxide Fuel Cells Applications
Authors: Huang Liang-Wei , Liu Chien-Kuo , Cheng Yung-Neng , Lee Ruey-Yi
Published: July 2021

Metal-supported solid oxide fuel cells (MS-SOFCs) exhibit better electrochemical performance than conventional ceramic-supported cells at lower temperature due to their exceptional thermal, electrical, and mechanical properties. MS-SOFCs can withstand rapid thermal cycling operation and make it practical for mobile applications. A reliable seal is essential for electrolyte/metallic interconnect joint in MS-SOFC applications. In the present study, we proposed an Ag-Ge alloy filler as a high-temperature brazing sealant for use in MS-SOFCs. Commercial ferritic stainless steel (Crofer22H) and La1-XSrXGa1-yMgyO3-
δ (LSGM) substrate were employed as metallic interconnect and electrolyte for this study, respectively. The adhesive and hermetic characterization for the electrolyte/metallic interconnect joint joined by the Ag-Ge alloy filler were examined by using high-temperature leak test at elevated temperatures. Results showed that the leak rate of LSGM/Crofer22H coupon is 5.0 x 10-4 mbar∙l/s/cm after aging at 750°C for 100 hours in He/air. In addition, SEM/EDS analyses also revealed that Ge element in the Ag-Ge filler is prone to diffuse toward Crofer22H and LSGM side, and thus improves the interfacial adhesion of the LSGM/Crofer22H joint.
Performance of Metal Supported SOFCs Operated in Hydrocarbon Fuels and at Low (<650˚C) Temperatures
Authors: Christensen Jens Ole , Hagen Anke , Sudireddy Bhaskar Reddy
Published: July 2021

The Ni/YSZ composite electrode is conventionally used for solid oxide cells, in electrolysis (SOEC) as well as fuel cell (SOFC) operation. For enhanced durability and C-tolerance, alternative fuel electrode materials are needed. In this paper, we compare the performance of two distinct Ni:CGO electrocatalyst coated A-site deficient lanthanum doped strontium titanate (La0.4Sr0.4Fe0.03Ni0.03Ti0.94O3, LSFNT) based anodes, integrated into metal supported cells (MSCs), to the SoA Ni/YSZ anode supported cell in fuel cell mode for the first time. The three cells were investigated electrochemically by impedance spectroscopy (EIS) and performance under applied current (iV-curves) at temperatures 750˚C, 700˚C, 650˚C, and at novel 620˚C in steam/hydrogen and methane/steam. Additionally, one of the MSCs was investigated in CO/steam. Furthermore, galvanostatic durability tests were conducted in 4% steam/hydrogen for the MS-cells at low temperature (650˚C) at medium-high fuel utilization (50%).
Lifetime Prediction and Rapid Design Evaluation of SteelCell® Stacks Using Advanced Multiphysics Modeling
Authors: Gawel Duncan , Leah Robert , Thandi Rajan , 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 durability testing is necessary it is not commercially viable when product development cycles are a small fraction of the product life. The application of SOC stacks to many applications can drive significant investments to repeat experimental validation for a change in operating conditions, a new application, 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 also incorporates a dynamic solver which allows through-life performance degradation prediction based on mathematical models derived from extensive experimental investigations into cell and stack degradation mechanisms. In this way stack operating life can be predicted under a particular set of operating conditions with limited testing.
Sizing Design and Simulation of an SOFC Propulsion System for Unmanned Aerial Vehicles
Authors: Xin Tong , Wang Yuqing , Shi Yixiang
Published: July 2021

The short flight endurance is one of the key obstacles for the application of unmanned aerial vehicles (UAVs). Applying the fuel cells as the propulsion system of UAVs instead of batteries can increase the energy density and further lead to a longer cruise duration. Compared to other kinds of fuel cells, the solid oxide fuel cell (SOFC) is advantageous for its ability to use hydrocarbon fuels with a much higher energy storage density than hydrogen. In this paper, a SOFC propulsion system is sized and designed for UAV applications. The power allocation between the SOFC and energy storage components was further studied. A system model was developed, including an SOFC stack, a catalytic partial oxidation (CPOx) reformer, an after burner, and heat exchangers, etc. The design parameters of the SOFC stack and other components were selected to meet the power and energy demand of the UAV. The model is proved to be a useful tool for the design and simulation of the UAV-SOFC systems.
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

Carbon deposition site in the Ni/YSZ was studied through microscale observation and first-principles calculation. Early stage of carbon deposition was appropriate reaction to determine the active site because the carbon worked as a visible marker. SEM observation showed that the carbon deposition was progressed not in the overall Ni surface but in the specific sites such as the Ni/YSZ interfaces at low temperature. STEM-HAADF showed that the graphite layer was not found on the Ni(111) surface but on the Ni(112) surface, indicating that the unsaturated step facets such as Ni(112) enhanced the carbon deposition. Similar trends were found in the first-principles calculation. The CH adsorption energy in the Ni(112) facet was higher than that in the Ni(111) facet. In addition, it was suggested that the YSZ structure also influenced the carbon deposition as well as the Ni facet.
Study on the Thermal-Electrical Balance of the kW-zclass SOFC Stack
Authors: Biao Li , Lyu Zewei , Han Minfang , Sun Kaihua , Sun Zaihong , Liu Yang
Published: July 2021

Heat and electricity are deeply coupled in solid oxide fuel cell (SOFC) stacks, and the balance and control between them are vital to the steady working condition and outputs. Therefore, studying the balance mechanism of heat and electricity is important to achieve the safe and stable operation of the SOFC stacks. In this paper, a semi-empirical simulation model of a kilowatt-level SOFC stack was established. Based on this model, the effects of different operating temperatures, flow rates, air to H2 ratios (AHR), and steam to carbon (S/C) ratios on the thermoelectric balance state of the SOFC stack were analyzed. Results show that the I-V curve can be separated into three parts: unbalance zone, unsustainable zone, and the self-heat balance zone by the self-heat balance voltage (SHBV) and the critical voltage (CV). The approximate voltage scope of the balance zone under different conditions is 0.6~0.9 V.
Revised Zero-Dimensional Model for a Solid Oxide Fuel Cell with Mo-Doped Ceria Anode Using Syngas as Fuel
Authors: Bravo Riquelme Diego , Diaz-Aburto Isaac , Colet Lagrille Melanie
Published: July 2021

A zero-dimensional model was implemented to simulate the performance of a solid oxide fuel cell (SOFC) with Mo-doped ceria (CMO) anode using humidified (3%v/v water) syngas (50%v/v H2 – 50%v/v CO) as fuel. The model was validated preliminarily using polarization data (cell voltage vs current density, ΔEcell vs j, curves) generated experimentally at 800ºC using a SOFC supported on the electrolyte (a 20 mm diameter, 250 μm thickness yttria-stabilized zirconia, YSZ, disc) with a 14 mm diameter CMO-YSZ|CMO anode and a 14 mm diameter LSM (lanthanum strontium manganite)|LSM-YSZ cathode, that was connected to a Gamry Reference 3000 potentiostat/galvanostat/ZRA using platinum mesh and wires. Open circuit voltage was modeled using a Nernst equation corrected by H2 and CO electrooxidation reactions selectivity at the anode, which was determined through the resolution of relevant mass balances as a function of the SOFC thermodynamics and kinetics.
Computational Modelling of Ceria-Based Solid Oxide Fuel Cell Electrolyte Materials
Authors: Ahmed Mohamed , Rodley David , Jones Thomas , Abdolvand Amin , Lightfoot Alison , Fruchtl Herbert , Baker Richard
Published: July 2021

A simulation methodology for calculating the lattice parameter and oxygen ion migration energy of ceria-based electrolyte formulations is devised. The results are analysed and benchmarked against experimentally obtained values to verify the efficacy of the simulation methodology. A total of 26, 2 x 2 x 2 samarium (Sm)- and gadolinium (Gd)-doped supercells of different compositions and doping profiles were modelled and simulated by molecular mechanics force field methods using CP2K. The results of the computational simulations are comparable with those obtained experimentally, especially when there are equal amounts of Sm and Gd dopants in the structure. Simulation results can also provide insights into the mechanisms of ionic conduction. The incongruence of the computational and experimental results is attributed to the limitations of the molecular mechanics force field methodology utilised, with the expectation that an ab initio density functional theory (DFT) calculation would yield closer conformance.
Elementary Reaction Kinetic Model of an Anode-Supported Syngas Fueled Solid Oxide Fuel Cell Considering the Carbon Deposition Effect
Authors: Zhang Ruiyu , Wang Yuqing , Shi Yixiang , Wang Yinan , Cao Haishan
Published: July 2021

A one-dimensional transient elementary reaction kinetic model of an anode supported solid oxide fuel cell (SOFC) fueled with syngas is developed considering the carbon deposition effect. This model incorporates the coupling effect of heterogeneous elementary chemical and electrochemical reactions, the electrode microstructure and the charge, and mass transport processes. The model is validated by both experimental I-V curves and electrochemical impedance spectra. The simulation results agree reasonably well with the experimental data. The numerical results of carbon deposition simulation indicate that the surface carbon coverage can be decreased by increasing the operating temperature and reducing the carbon dioxide, methane, or carbon monoxide in the fuel.
Modeling Nickel Microstructural Evolution in Ni-YSZ Electrodes Using a Mathematical Morphology Approach
Authors: Moussaoui Hamza , Nakajo Arata , Rinaldi Giorgio , Hubert Maxime , Laurencin Jérôme , Van Herle Jan
Published: July 2021

Microstructural evolution in the electrodes plays an important role in the durability of Solid Oxide Cells (SOCs). The metallic phase in the fuel electrodes made of Nickel and Yttria-Stabilized Zirconia (Ni-YSZ) is not stable in operation as it has a high mobility and a rather low wettability to YSZ. To enable long term durability prediction and improve the anode performance, it is necessary to understand its microstructural evolution under different operating conditions. This contribution presents a 3-D geometrical model based on morphological operations. 3-D microstructures of as reduced and aged electrodes were reconstructed by X-ray nanotomography and used to assess the relevance of the model verification. The low computational time of the morphological model allows generating a large database of numerical microstructures for the study of the impact of Ni evolution on the microstructural properties.
Recent Achievement of Degradation Analyses in Japanese National Project: High Efficiency and Dynamic Operation Effects on the Durability of SOFC Stacks
Authors: Horita Teruhisa
Published: July 2021

In this report, recent achievements of the Japanese national projects (NEDO projects) are presented, especially on the rapid evaluation methods for cell-stack degradation (2018-2019) and the “Development of advanced evaluation and analysis technologies for the durability of Solid Oxide Fuel Cells stacks (2020-)”. The durability of practical cell-stacks was examined under high fuel utilization (Uf) conditions (over 80%) and dynamic load cycling operations at different kinds of cell-stack geometry: flat-tubular and planer. All stacks showed relatively stable performance even in high Uf and load cycling. The degradation mechanism of Ni-YSZ anode cermet was especially examined in terms of Ni migration and morphology change at the Ni/oxide contact. It was found that the Ni migration and morphological change were small in the practical cell-stacks although a significant change was reported in several tests. The discussion on the relationship between performance degradation and morphological change was made under high water vapor conditions.
Degradation Analysis of Long-Term Solid Oxide Fuel Cell Stacks with Respect to Chromium Poisoning in La0.58Sr0.4Co0.2Fe0.8O3-δ and La0.6Sr0.4CoO3-δ Cathodes
Authors: Fang Qingping , Menzler Norbert , Blum Ludger
Published: July 2021

Chromium poisoning as a result of Cr evaporation from the metallic components and the subsequent deposition on the cathode (i.e., air) side is one of the most critical degradation mechanisms in solid oxide fuel cell (SOFC) stacks. Recently, the LSC cathode (i.e., La0.6Sr0.4CoO3-δ) exhibited more promising results in both fuel cell and electrolysis modes than the LSCF (i.e., La0.58Sr0.4Co0.2Fe0.8O3-δ) due to its higher ionic conductivity, despite a relatively larger thermal expansion coefficient (TEC). Furthermore, it has been reported that the oxygen surface exchange kinetics and Sr stability/activity of LSC may imply higher resistance against Cr poisoning by comparison to LSCF. For these reasons, long-term stack operation with both LSCF and LSC cathodes was performed for two different stack designs. The degradation behavior of the stacks with respect to Cr poisoning was analyzed with the support of electrochemical impedance spectroscopy and post-mortem analysis.
Ni/CGO-Based Electrolyte-Supported Cells During Co-Electrolysis: The Role of Feed Gas Impurities
Authors: Riegraf Matthias , Surrey Alexander , Costa Rémi
Published: July 2021

In the present study, durability aspects of state-of-the-art Ni/CGO-based electrolyte-supported cells are investigated in steam electrolysis, dry CO2 electrolysis, and co-electrolysis operation under various operating conditions by means of current-voltage characteristics and electrochemical impedance spectroscopy, and high performance was demonstrated. Electrochemical steam reduction kinetics were shown to be faster than carbon dioxide reduction. Performance in co-electrolysis was observed to be close to performance in steam electrolysis. Furthermore, strong degradation of the Ni/CGO fuel electrode surface process was observed in CO/CO2 atmosphere under the absence of current which suggests the presence of impurities in the feed gas that poison the electrode surface.
Redox-Cycling – A Tool for Artificial Electrochemical Aging of Solid Oxide Cells
Authors: Burdin Blagoy , Sheikh Asrar , Krapchanska Milena , Montinaro Dario , Piccardo Paolo , Spotorno Roberto , Vladikova Daria
Published: July 2021

In this work a procedure for accelerated stress tests of Solid Oxide Cell (SOC) by artificial aging of the anode via redox cycling is presented. This approach eliminates the interrelation of different degradation processes and ensures a clear picture of the anode degradation on the total cell performance. The level of oxidation is monitored in situ on bare anode samples by impedance measurements of the Ni network resistance changes during oxidation/reduction cycling which ensures governing of the oxidation level with high reproducibility by selection of appropriate experimental conditions. Once fixed on bare anode samples, the selected redox cycling regime is further applied in full cell configuration. The developed methodology is evaluated by comparative analysis of current-voltage and impedance measurements of artificially aged and calendar aged button cells. The results for 8 redox cycles are comparable to those obtained for more than 600 hours operation in standard conditions.
N-Doped Biochar as H2s Adsorbent for the Biogas-Fueled SOFC
Authors: Setiawan Hendrik , Sakamoto Mio , Shiratori Yusuke , Fujisaki Takaya
Published: July 2021

The reliability of a biogas-fueled SOFC depends directly on the purity of the biogas. To prevent performance degradation caused by H2S poisoning, this study aimed to develop a nitrogen (N)-doped carbon derived from biomass feedstock using the digested liquid as the N source, which acted as an adsorbent material to reduce the H2S concentration in biogas to below the sub-ppm level. Biochar (BC) derived from rice husk (RH) treated with 25 vol% NH3 gas (balanced with N2) at 900°C for 120 min, RH-BC(N900-120), exhibited the largest H2S breakthrough capacity (APCH2S(0)
) of 8.02 mg H2S g-BC−1 and a total H2S adsorption capacity (ACPH2S
) of 9.58 mg H2S g-BC−1. The largest ACPH2S
, 23.0 mg H2S g-BC−1, was obtained for the RH-BC treated with NH3 evaporated from a 10 wt% NH3 solution (simulating a concentrated digested liquid) at 850°C for 270 min, RH-BC(EN850-270), with an APCH2S(0)
of 3.96 mg H2S g-BC−1. For a strongly N-doped BC such as RH-BC(N900-120), the formation of surface sulfate after H2S adsorption was more significant compared to a mildly N-doped BC, i.e. RH-BC(EN850-270), in which the interaction of the surface with H2S was moderately weakened, preventing the blockage of micropore openings by the accumulation of sulfate. Consequently, the H2S molecules could be adsorbed into the micropores, resulting in a higher ACPH2S
.
Thin Film Barrier Layers with Increased Performance and Reduced Long-Term Degradation in SOFCs
Authors: Bernadet Lucile , Baiutti Federico , Martinelli Francesca , Torrell Marc , Morata Alex , Montinaro Dario , Tarancón Albert
Published: July 2021

This work presents the results from the optimisation of a CGO barrier layer deposited by PLD. The layer annealing temperature was first defined and led to the fabrication of large-area cells (80 cm2) that were aged for 14000 h in a stack operated in SOFC mode. Low quantity of SrZrO3 were detected proving the barrier layer good blocking ability. Moreover, no evidences of barrier layer degradation could be observed by the post-mortem analysis.At the light of those promising results, the thickness of this PLD barrier layer was adjusted by finding the optimal combination between the protective role of the diffusion barrier layer, a good performance and the reduction of the PLD deposition time. It is shown that the barrier layer thickness has no impact on the electrochemical performance which would allow the use of thinner layers corresponding to a drastic reduction of its deposition time.
Operando Diagnostics of Solid Oxide Fuel Cell Stack Via Electrochemical Impedance Spectroscopy Simulation-Informed Machine Learning
Authors: Le Giang Tra , Mastropasqua Luca , Adler Stuart B. , Brouwer Jack
Published: July 2021

In this work, we apply a machine learning approach to solid oxide fuel cell (SOFC) system diagnostics. Instead of fitting electrochemical impedance spectroscopy (EIS) into a physics based model or equivalent circuit, we train machine learning models to recognize failures from a database of simulated EIS. We use a coarse-grained physics-based model to simulate stack EIS under three different failure modes: fuel maldistribution, delamination, and cathode gas crossover to anode channel. Synthesized machine learning classification models successfully recognize these different degradation mechanisms in simulated data across different operating conditions. We are also able to differentiate these failures from the uniform degradation that tends to occur with SOFC over time. These encouraging results prompt our current effort to implement machine learning diagnostics methods on experimental EIS collected on SOFC short stack.
Shrinkage Behavior, Thermal Expansion Behavior, and Electrical Conductivity Study of Samarium Doped Ceria Electrolytes
Authors: Lakhanlal Lakhanlal , Dasari Hari Prasad , M.B. Saidutta
Published: July 2021

In the present study, sintering behavior and electrical conductivity of Sm doped Ceria (SDC) and multi-doped (Sm/Pr/Li) Ceria electrolytes synthesized by microwave-assisted co-precipitation method is studied. SDC green pellet displayed a unimodal shrinkage behavior with a linear shrinkage of 15.67% along with a slight dedensification above 1350℃. An increase in electrical conductivity with an increase in sintering temperature from 1200 to 1300℃ was observed. Further increasing the sintering temperature (1400 and 1500℃) electrical conductivity decreased, which could be due to dedensification (as observed in sintering behavior). At 600℃, the electrical conductivity of SDC1200 is around 1.34 × 10-2 S cm-1. The sintering temperature is drastically decreased to 850℃ from 1200℃ with the addition of Li, and the electrical conductivity is increased with the addition of Pr to SDC electrolytes. At 600℃, the electrical conductivity of 3Li-SPDC850 sintered at 850℃ is 1.44 × 10-2 S cm-1. The thermal expansion coefficient (TEC) of the electrolytes studied were in the range of 12.7 × 10-6 to 17.6 × 10-6 K-1.
TEM Characterization of Long Term Aged Interconnect Oxide Layers from Real Stack
Authors: Poitel Stéphane , Daviran Samaneh , Bianco Manuel , Walter Christian , Herbrig Kai , Van Herle Jan
Published: July 2021

Interconnects from real SOFC stacks operated for 9000h and 20000h are characterized by means of SEM and TEM. This study focuses on the air side of the interconnect, which has been coated with manganese cobalt spinel oxide (MCO) doped with iron. Differences between the zones of air channel and interconnect rib are highlighted. Iron particles are found in the thermally grown oxide (TGO) exposed to the air channel. Manganese-rich crystals are observed close to the steel bulk for the rib contact zone, and in the bottom part of the TGO for the air channel zone. Cobalt is segregating at grain boundaries in the MCO after 20000h. More investigation is necessary to fully understand all mechanisms but the additional information gathered in the present study should help in better designing accelerated testing and modelling.
Development of an Isotopic Oxygen Exchange Setup Operating Under High Pressure: Preliminary Measurements Performed on Ln2NiO4+d (Ln=La, Pr, Nd, MIEC) Oxides
Authors: Flura Aurélien , Laurencin Jérôme , Fourcade Sébastien , Mauvy Fabrice , Vibhu Vaibhav , Salvetat Jean-Paul , Mouginn Julie , Bassat Jean-Marc
Published: July 2021

MIEC (Mixed Ionic Electronic Conductors) used as oxygen electrodes in Solid Oxide Cells are characterized by both high oxygen diffusion (D) and surface exchange (k) coefficients. To date, the reported measurements have been performed at ambient pressure and even below. However, to reach a higher efficiency at the system level, it would be helpful to operate the Solid Oxide Electrolysers under high pressure. A preliminary study is therefore mandatory, to assess the oxygen reduction/oxidation and the transport properties of the electrodes materials when submitted to high pressure. Then, an innovative setup able to operate up to a total pressure of 50 bar has been developed. Its technical characteristics will be described here. This setup has been used to characterize the properties of nickelates with MIEC properties. Oxygen exchanges have been performed in the range 500 < T°C < 700, under p(O2) ~ 6.5 bars. Preliminary results (oxygen over-stoichiometry, D* and k* coefficients) obtained on Ln2NiO4+
d (Ln=La, Pr, Nd) oxides are presented and discussed.
Unsupervised Generative Adversarial Network for 3-D Microstructure Synthesis from 2-D Image
Authors: Sciazko Anna , Komatsu Yosuke , Shikazono Naoki
Published: July 2021

Understanding and modelling complex phenomenon in solid oxide fuel cell electrodes require information about their three dimensional microstructures. However, measuring the 3-D micro- and nano-structures requires complex and time-consuming data acquisition technique such as focused ion beam - scanning electron (FIB-SEM) tomography. Meanwhile, obtaining a single 2-D cross-sectional SEM image is relatively simple. A new algorithm for synthetic 3-D microstructure generation from 2-D cross-section is proposed in the present study. The algorithm is based on the generative adversarial network (GAN) composed of a 3-D generator and a 2-D discriminator, which uses only 2-D images as a training data. The applicability of the proposed method is tested on nickel (Ni) – gadolinium doped ceria (GDC) anodes. The synthetic 3-D microstructures are compared with those obtained from FIB-SEM. The proposed method can be easily adapted for any type of materials and imagining techniques.
Deconvolution of Gas Diffusion Polarization in Ni/Gadolinium-Doped Ceria Fuel Electrodes
Authors: Grosselindemann Cedric , Russner Niklas , Dierickx Sebastian , Weber André
Published: July 2021

The deconvolution of physicochemical processes in impedance spectra of SOCs with nickel/ceria fuel electrodes is challenging as gas diffusion strongly overlaps with the electrochemical processes at fuel and air electrode. To overcome this issue, symmetrical cells were applied and the gas diffusion process at the fuel electrode was quantified by altering the inert component (nitrogen/helium) in a ternary fuel gas mixture. An effective gas transport parameter considering microstructural and geometrical features was derived, enabling a precise quantification of polarization resistances related to gas diffusion and hydrogen electrooxidation. The obtained values were applied to parameterize an existing dc cell model. The model validation in fuel cell and electrolyzer mode showed an excellent agreement between measured and simulated current/voltage characteristics over a wide range of technically meaningful gas compositions and operating temperatures.
An Investigation of the Redox Stability of an Anode-Supported SOFC Stack Using Acoustic Emission Monitoring
Authors: Rangel-Hernandez Victor , de Haart Ute , Fang Qingping , Schäfer Dominik , Thaler Florian , Peters Ralf , Blum Ludger
Published: July 2021

The mechanical stability of an SOFC stack is compromised when its cells operate in oxidation-reduction (Redox) environments. Previous studies, based mainly on voltage-current or electrochemical impedance measurements, showed that cell performance degraded upon redox cycling above 600°C. Therefore, the purpose of this work is to investigate the Redox process and the stability of a SOFC stack applying the Acoustic Emission (AE) monitoring technique. The investigation includes the interpretation of AE events and signals considering their waveform and frequency content.
Optimization of Contact Cathode Composition Based on La0.8Sr0.2MnO3±δ for SOFC Stacks
Authors: Matveev Danila , Fedotov Yuri , Ivanov Alexey , Agarkova Ekaterina , Kharton Vladislav , Bredikhin Sergey Ivanovich
Published: July 2021

The formation of stable contact layers with minimum electrical resistivity at the electrode/interconnector interface is an important task for planar SOFC stack fabrication. This work was centered on the search for optimum processing conditions of the La0.8Sr0.2MnO3±δ (LSM) based contact pastes without inorganic additives. The ball-milling conditions and contact paste composition were optimized taking into account the LSM particle size, sintering, a possibility of partial phase decomposition, and electrical conductivity of the resultant cathode contacts. Testing of the model SOFC stack with Crofer 22H interconnectors revealed sufficient adhesion, porosity, conductivity, and stability of porous LSM contact layers.
Conducting Property and Performance Evaluation of LNF as Cathode Current Contact Layer in Solid Oxide Fuel Cell
Authors: Lyu Qiuqiu , Wang Yu , Zhu Tenglong , Sun Kaihua , Sun Zaihong , Bu Yunfei , Zhong Qin , Han Minfang
Published: July 2021

In this work, LaNi0.6Fe0.4O3 is prepared and applied as cathode current contact layer on anode supported SOFC. The conducting property of both thin (~7μm) and thick LNF film (~1mm) are tested using lateral Van der Pauw DC conductivity test method and direct DC conductivity test method. Results show that the LNF layer prominently improves electrochemical performance of industrial sized anode supported single cell by ~29% at voltage of 0.7V at 800 and 750℃. During long-term annealing, 950℃ pre-fired LNF film performs more stable conducting property than 900℃ prepared sample. While the area specific resistance of LNF thick film shows a small increasing by ~0.272% per 1000 hours at 750℃, under constant current load. Suggesting good application prospects in planar solid oxide fuel cell stack.
Investigation of the Redox Behaviour of Double Perovskite PrBaMn2O5+δ
Authors: Felli Andrea , Trovarelli Alessandro , Boaro Marta
Published: July 2021

A multi-analytical approach (in situ X-ray diffractometry, XRD, temperature programmed reduction TPR, thermogravimetry TGA) was used to deeply study the phase transition between the Pr0.5Ba0.5MnO3-
δ (m-PBM) and the double layered perovskite PrBaMn2O5+
δ (l-PBM). m-PBM sample was prepared by an auto-combustion based citrate procedure and exposed to consecutive reduction and oxidation cycles at high temperature to understand the effect of oxidizing and reducing atmospheres on structural changes and stabilization of the layered double perovskite. XRD analysis showed the existence of a pseudo cubic structure (c-PBM), which is formed from the direct oxidation of l-PBM. TPR results confirmed the c-PBM to l-PBM reversibility to the redox processes, and the TGA characterization showed a fast transition between l-PBM to c-PBM. The oxidation of l-PBM to c-PBM seems pivotal for the stabilization of the layered reduced structure. The results are discussed in the perspective to develop versatile electrodes for SOEC/SOFC applications.
Investigation of La2-XSrxNi0.8Co0.2O4+d (0.0 ≤ x ≤ 0.2) Materials as Oxygen Electrodes for Solid Oxide Cells
Authors: Unachukwu Ifeanyichukwu Daniel , Vibhu Vaibhav , Vinke I. C. , Eichel Rüdiger-A. , De Haart L. G. J. (Bert)
Published: July 2021

Lanthanide Nickelates Ln2NiO4+δ (Ln = La, Pr or Nd) have drawn significant attention as oxygen electrodes for solid oxide cells (SOCs) due to their mixed ionic and electronic conducting (MIEC) properties. They exhibit very good electro-catalytic activity as well as high values for the oxygen diffusion coefficient (D*
) and surface exchange coefficient (k*
). Earlier reported results show that the partial substitution of Co2+ at B-site in La2Ni1−x
Co
x
O4+δ lead to an enhancement in the transport and electrochemical properties of the material. The present study aims to investigate the effect of Sr2+ substitution at the A-site in La2-x
Sr
x
Ni0.8Co0.2O4+δ in order to further investigate the structural, physico-chemical and electrochemical properties of this class of materials. The TGA results shows a decrease in delta value with increase in Sr doping, while the EIS data analysis of the symmetrical half-cells shows an increase in polarization resistance (R
p) with increasing Sr-content.
Effect of Sn, Cu, and Ag Modification on Electrochemical Performance and Carbon Tolerance of Biogas-Operated Ni/YSZ and Ni/ScCeSZ SOFC Anodes
Authors: Jiang Zeyu , El-Kharouf Ahmad , Steinberger-Wilckens Robert
Published: July 2021

The Ni-based anodes with different electrolyte (YSZ and ScCeSZ) were modified by 1 wt% Sn, Ag, and Cu. Dopant precursors were added to porous anode via infiltration technique. Prepared cells were tested under simulated biogas with fuel composition of CH4:CO2:N2=2:1:1 at 750°C. Cell operational stability was significantly improved with the presence of Sn or Ag in the anode. More importantly, Sn-doped cell exhibited comparable maximum power density in biogas as with hydrogen. Carbon deposition on Sn and Ag-doped anode surface was successfully prevented, hence, using Sn and Ag is a promising approach to improve Ni-based anode cells under dry methane reforming conditions.
Ruthenium-Exsolution Catalyst for Dry Reforming of Biogas
Authors: Frantz Cedric , Rumpf Lionel , López Solá Alex , Wang Ligang , Naeem Muhammad Awais , Müller Christoph R. , Van Herle Jan
Published: July 2021

When biogases are directly used as fuels in SOFCs, catalytic reforming of methane into hydrogen and carbon monoxide occurs at the nickel anode. This may expose the anode to localized cooling and a high risk of carbon deposition. These issues can be tackled by preprocessing the biogas. Diluting it with steam or CO2 recovered from the SOFC anode off-gas may suppress the risk of carbon deposition whereas reforming it externally can protect the cell from thermal instabilities while offering additional protection against contaminants. Ruthenium has an outstanding catalytic activity with demonstrated coking resistance. Its cost however limits its use. In this work, dry reforming of diluted biogases was performed on a low-ruthenium-exsolution catalyst. An approach by total material balance allowed to determine near 100% methane conversion at GHSV up to 2000 h-1 while the reaction was close to the computed thermodynamic equilibrium.
Electrochemical Characteristics of SOFC Anodes Operated at High Fuel Utilization
Authors: Matsui Toshiaki , Fujinaga Tomoki , Ozeki Takashi , Shimizu Ritsuki , Muroyama Hiroki , Eguchi Koichi
Published: July 2021

High energy conversion efficiency in solid oxide fuel cell (SOFC) systems can be achieved by improving the fuel utilization. However, when the SOFCs are operated under high fuel utilization, the downstream part of the anode is exposed to high steam concentration and hence high P(O2) atmosphere. This has a negative impact on the stability of Ni-based cermet anodes. At this stage, no reports dealt with the degradation phenomena of the anode under such severe conditions. In this study, we aimed to clarify degradation phenomena at the downstream part of practical cells operated at high fuel utilizations by using bottom cells. The change in electrochemical properties of single cells was monitored during discharge operation with supplying fuel gases that simulated severe conditions.
Electrochemical Reduction of H2O and CO2 Using Anode Supported SDC Cells
Authors: Zhang Xinge , Fahlman Jason , Robertson Mark , Yao Peter
Published: July 2021

In this contribution, we studied electrochemical reduction of H2O and CO2 at reduced temperatures using anode supported SDC cells. We observed that the SDC cell voltage was 1.16V under electrochemical reduction of H2O and 1.17V under electrochemical reduction of CO2 at 500oC, 0.5A cm-2. The cell showed no degradation during a short term (72hr) stability test under the CO2 electrochemical reduction condition. It was noticed that the SDC cells showed much better cell performance in the electrolysis cell (EC) mode than in the fuel cell (FC) mode in term of polarization. It was also found that the impedance of the SDC cell changed dramatically with applied current. At high applied EC current the cell became more like a pure inductor (or a resistor), i.e., the semicircle representing the electrochemical polarization was decreased, and the electrolyte bulk resistance was also reduced substantially. It implies that the SDC cell under the EC mode becomes more electronically conductive, and the resistance is varied with the applied current. GC analysis of fuel side gas composition revealed that CO2 conversion rate was low, and almost irrelevant to the applied current. The corresponding faradic efficiency is extremely low, indicating a severe internal shorting problem under the EC tested conditions. Therefore, we conclude that the anode supported SDC electrolyte cell is not feasible for SOEC application even at a reduced temperature.
Redox Stability of Tubular Solid Oxide Cell Using LaGaO3 Electrolyte Film Prepared by Dip-Coating
Authors: Tan Zhe , Ishihara Tatsumi
Published: July 2021

Reversible operation of SOFCs is an important subject in renewable energy and is urgently needed at present. A NiO-YSZ tubular cell using a La0.9Sr0.1Ga0.8Mg0.2O3−δ electrolyte was prepared by dip-coating and its reversible operation was studied. Effects of Ce infiltration into the Ni-YSZ substrate was also studied and it was found that Ce infiltration is highly effective for increasing cell performance and stability in fuel cell and electrolysis modes. Cyclic operation of the LSGM tubular cell in SOEC and SOFC modes using a Ce infiltrated Ni-YSZ substrate was measured at 600℃ under 17%steam-25%H2 in Ar. During 100 redox cycles at ±0.1 A cm-2, the OCV remained almost unchanged from the initial value. The SOFC operating potential decreased slightly with increasing cycles, however, the degradation rate was significantly decreased by Ce infiltration.
Improvement in Power Density of Protonic Ceramic Fuel Cells with Yb Doped BaZrO3 Electrolyte
Authors: Shimada Hiroyuki , Yamaguchi Yuki , Sumi Hirofumi , Nomura Katsuhiro , Shin Woosuck , Mizutani Yasunobu
Published: July 2021

This paper reports our development of protonic ceramic fuel cells (PCFCs) with BaZr0.8Yb0.2O3−δ
(BZYb) electrolyte. Although PCFCs can theoretically achieve ultra-high energy-conversion efficiency for power generation, higher power density even at lower temperatures below 600°C is required to widespread application. Here, a zirconate-based oxide of BZYb was selected as electrolyte material of PCFCs because of its high chemical stability against CO2. Also, cost-effective conventional wet processes were used to fabricate the PCFCs. High-temperature co-sintering successfully produced a dense and thin BZYb electrolyte. The PCFC showed a stable operation for 400 h without significant degradation. Investigation into changing parameters of large-size PCFCs (50 × 50 mm) such as anode porosity, interlayer function, electrolyte thickness, and cathode material improved the power density of the PCFCs with BZYb electrolyte. At 600°C, the power density reached 0.38 and 0.48 W cm−2 at 0.85 and 0.75 V, respectively.
Evaluation of Reaction Mechanism of PCFC Composite Cathodes by Utilizing Patterned Thin Film Model Electrodes
Authors: Diao Zhuo , Nishidate Katsuya , Imaizumi Takaaki , Kimura Yuta , Nakamura Takashi , Mikami Yuichi , Kuroha Tomohiro , Yashiro Keiji , Kawada Tatsuya , Amezawa Koji
Published: July 2021

For detailed and quantitative analysis of the reaction mechanism in a composite cathode for proton-conducting ceramic-electrolyte fuel cells (PCFCs), a new type of model electrode was proposed. In this work, patterned thin film composite electrode was designed to model the reaction in a porous composite cathode of PCFCs while simplifying the complicated microstructures. The model composite electrode was fabricated with La0.6Sr0.4CoO3-δ
(LSC) and BaZr0.8Yb0.2O3-

δ
(BZYb) as an MIEC cathode and an electrolyte materials, respectively, by helps of photolithography and pulsed laser deposition. By utilizing the model composite electrode, one can expect to directly evaluate contributions of addition of electrolyte particles into composite cathode and to understand the mechanism of the cathodic reaction further.
Effect of Ce/Zr Ratio on Thermal and Chemical Expansions and CO2 Resistance of Rare Earth-Doped Ba(Ce,Zr)O3 Perovskite-Type Proton Conductors
Authors: Nomura Katsuhiro , Shimada Hiroyuki , Yamaguchi Yuki , Shin Woosuck , Okuyama Yuji , Mizutani Yasunobu
Published: July 2021

The crystal structures, thermal expansions, chemical expansions, and CO2 resistances of Ba(Ce0.7Zr0.1Y0.1Yb0.1)O3-δ (BCZYYb7111) and Ba(Ce0.4Zr0.4Y0.1Yb0.1)O3-δ (BCZYYb4411) have been investigated via high-temperature X-ray diffraction (HT-XRD) in controlled atmospheres (dry N2, wet N2, and dry 33.3 vol% CO2 - 66.6 vol% N2) on cooling from 1173 to 298 K. Two phase transitions, cubic to trigonal and trigonal to monoclinic, were observed for BCZYYb7111, whereas one phase transition, cubic to trigonal for BCZYYb4411. BCZYYb7111 and BCZYb4411 exhibited the linear thermal expansion coefficients of 10.6 × 10-6 K-1 and 9.8 × 10-6 K-1 between 773 and 1173 K in dry N2, respectively. The maximum chemical expansion rates of 0.33 % and 0.30 % were observed at 773 K for BCZYYb7111 and BCZYYb4411, respectively. BCZYYb4411 having lower Ce/Zr ratio and higher symmetry showed higher CO2 resistance than BCZYYb7111.
Development of Proton Conducting Ceramic Cells in Metal Supported Architecture
Authors: Sata Noriko , Han Feng , Zheng Haoyu , Dayaghi Amir Masoud , Norby Truls , Stange Marit , Semerad Robert , Costa Rémi
Published: July 2021

Metal-Supported (MS) architecture offers various advantages over state-of-the-art ceramic supported SOCs, such as high tolerance towards thermal/redox cycling that are key features for flexible and reliable operation in high temperature fuel cell and electrolysis applications. Our target is to develop Proton-conducting Ceramic Cells (PCC) in MS architecture, of which combination can provide potentially high performances, mechanical stability, and flexibility for wide range of electrochemical applications. The key challenge in the development of MS-PCC is to find a feasible process to fabricate gas-tight electrolyte on the porous metal substrate without degrading the metal support and the electrolyte. Our strategy is implementing multilayers combining wet chemical processes below 1000°C for the functional electrode and dry Physical Vapor Deposition (PVD) techniques below 800°C for the gas-tight electrolyte coating. In this paper, we present our recent results in the development of MS-PCC half cells. The materials selection for MS and PCC components, functional layer processing, and electrolyte layer deposition techniques are discussed.
Electrically Conductive and Protective Coating Reaction with LSCF Material
Authors: Choi Jung Pyung , Bonnett Jeff , Canfield Nathan , Hardy John S
Published: July 2021

Ferritic stainless-steel interconnect materials are used in intermediate or high-temperature SOFCs because of their oxidation resistance, high formability, and low cost. Their corrosion resistance is due to the formation of a protective chromium oxide scale during operation. However, the protective oxide layer produces Cr-containing volatile species at SOFC operating temperatures and conditions, which can cause cathode poisoning. Spinel coatings have been developed to prevent cathode poisoning while maintaining an electrically conductive pathway through SOFC stacks. Generally, Mn-Co-O spinel has been the material of choice, but PNNL has developed an Mn-Cu-O spinel protective coating to remove the costly Co and enhance the electrical conductivity. This paper will focus on the electrically conductive coating’s compatibility with LSCF in high-temperature operating environments.