bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance and Stability of Solid Oxide Cell Stacks in CO2-Electrolysis Mode
Authors: Thaler Florian , Fang Qingping , de Haart Ute , De Haart L. G. J. (Bert) , Peters Ralf , Blum Ludger
Published: July 2021

Compared to low-temperature electrolysis techniques, solid oxide cell (SOC) technology has attracted growing interest in Power-to-X scenarios based on renewable energy due to its high efficiency, reversibility, and the possibility of simultaneously converting CO2 and H2O into syngas, a chemical precursor for synthetic fuels or intermediates such as methanol. Furthermore, SOCs can also be operated in CO2 electrolysis mode in order to produce pure CO, which is in great demand in the chemical and steel industries. Based on previous experience with fuel cell, steam,- and co-electrolysis operation, the electrochemical performance and durability of planar fuel electrode-supported SOC stacks are investigated with a focus on CO2 electrolysis. Their current-voltage characteristics and electrochemical impedance have been measured in both CO2 and co-electrolysis modes. The main aim of these investigations was to gain insights into the electrochemical processes and limitations of the currently used electrodes during CO2 electrolysis, and to understand the general degradation mechanisms of cells under different conditions. Using state-of-the-art cells, the stack can be operated at 800°C with a current density of -1000 mA cm-2 below cell voltages of 1.4 V in a CO2/CO (1:1) mixture. Based on the findings thus far, some promising approaches with respect to the optimization of fuel electrode microstructures and reaction kinetics to increase the performance and durability of the cells under CO2 electrolysis operation are discussed.
Reversible Solid Oxide Cells: Durability of Fuel Electrodes Against Voltage Cycling
Authors: Natsukoshi Katsuya , Miyara Kengo , Tachikawa Yuya , Matsuda Junko , Taniguchi Shunsuke , Harrington George Frederick , Sasaki Kazunari
Published: July 2021

Reversible Solid Oxide Cells (r-SOCs) are an attractive electrochemical energy conversion technology that can act as both a Solid Oxide Fuel Cell (SOFC) for power generation, and a Solid Oxide Electrolysis Cell (SOEC) for steam electrolysis. Unfortunately, Ni-zirconia cermet, which is widely used in SOFCs, has the problem that the electronically conductive phases, Ni, agglomerates due to redox reactions and breaks the conductive path, resulting in performance degradation. In this study, we fabricated an alternative fuel electrode with a stable conductive structure using both an ionic conductor Ce0.9Gd0.1O2 (GDC) and an electronic conductor Sr0.9La0.1TiO3 (LST), and we co-impregnate Ni and GDC to the fuel electrode using only Ni as an electrocatalyst. The durability of the conventional fuel electrode and our alternative fuel electrode was compared and evaluated, and the potential of the alternative fuel electrode material was demonstrated.
Comparison of Reversible SOC-Based Renewable Energy Storage Systems for the Netherlands and India
Authors: Amladi Amogh , Singh Shalini , Woudstra Theo , Aravind P.V.
Published: July 2021

The present study explores a hybrid energy storage system (HESS) for a microgrid, with Li-ion batteries for short-term storage coupled with a reversible solid oxide cell (rSOC) system for seasonal energy storage in hydrogen. A comparison of system size and capital cost shows that using a HESS leads to significant savings compared to a system with only batteries, with a capital cost reduction of up to 75 %. The study also reveals that Jodhpur (India) has greater needs for seasonal storage, and sees greater benefits from the use of a HESS than a temperate region like Groningen (Netherlands), due to the very high variability of wind energy, combined with the high share of wind energy in India. This shows that reversible solid oxide cell systems are a serious contender for energy storage in different climatic regions.
Effect of Microstructure of the Anode Support Tubes Towards SOFC Performance
Authors: Sahu Sulata , Panthi Dhruba , Feng Hai , Du Yanhai
Published: July 2021

This manuscript describes the effect of microstructure of the anode support tubes (AST) fabricated by techniques such as freeze casting, isostatic press, and additive manufacture; towards the SOFC performance. A direct correlating has been observed between the performance of the cell and the anode support tube microstructure. Under similar test conditions, cells with higher interconnected pores were better in delivering the fuel towards the electrolyte and had a higher power generation capacity. The isolated pores in the tubes had little/no contributions towards the fuel cell performance. The tested cell had the following configuration: Ni+YSZ/Ni+10Sc1CeSZr/10Sc1CeSZr/SDC/SDC+LSCF/LSCF.
Research Needs for the Solid Oxide Electrolyzer (SOEC) with a Proton-Conducting SOEC (H-SOEC) Electrochemical Hydrogen Compressor (EHC) Energy Conversion Network (ECN)
Authors: Williams Mark , Song Xueyan , Gemmen Randall
Published: July 2021

A high temperature solid oxide electrolysis cell (SOEC) for electrolysis of water is paired with a H-SOEC for hydrogen compression (EHC). SOEC and EHC have been integrated into an electrochemical network (ECN) in a flow-series configuration and then simulated and analyzed. Adding heat and minimizing area specific resistance (ASR) would be highly desirable for further developing highly-efficient SOEC+EHC ECN’s. It is important to note there is a maximum possible heat generation rate with a given ASR when operated below the thermoneutral point. There is a maximal heat addition rate for optimal efficiency of the SOEC, and it is not at thermoneutral. Many developers have expressed interest in the thermal management of electrolyzer cells and in the possible existence of such an optimum. It is important to understand in general that heat removal can allow an increased hydrogen production rate over the thermoneutral path at constant temperature. For this reason, the SOEC+EHC ECN was simulated over a range of currents and ASR’s to determine the heat addition or removal required. If the internal resistance of an SOEC could be lowered sufficiently via the development of new, high-performing materials, the efficiency of hydrogen production could be very high, especially when supplementary heat is provided from solar or other waste heat sources such as nuclear or coal power plants. It is remarkable that a quarter to a third of the energy for the combined high-temperature electrolysis and hydrogen compression system could be provided by solar, nuclear, or coal.
Boundaries of High-Temperature Co-Electrolysis Towards Direct CO2-Electrolysis
Authors: Wolf Stephanie Elisabeth , Dittrich Lucy , Nohl Markus , Foit Severin , Vinke Izaak , De Haart L. G. J. , Eichel Rudiger-A
Published: July 2021

In this work, the transition boundary of high-temperature co-electrolysis towards pure CO2-electrolysis was investigated. AC and DC measurements with H2O concentrations from 0.0%eq to 39.7%eq led to the identification of the underlying electrochemical processes. Comparison of CO2 conversion in the (R)WGS reaction with electrochemical CO2 reduction by means of area specific resistance (ASR) showed that gas composition determines the dominant reduction reaction (H2O or CO2 reduction). The cell performance of CO2-electrolysis was found to be comparable to co-electrolysis in the boundary region up to around 4.7 %eq H2O. The threshold for the perception of CO2-electrolysis during co-electrolysis has been established to be around 31.7 %eq H2O. The hypothesis that pre-domination of CO2-electrolysis increases with decreasing H2O concentrations below this boundary limit was underlined by measurement results.
A Framework for Characterizing Commercial Solid Oxide Electrolysis Stacks Using Electrochemical Impedance Spectroscopy and Equivalent Circuit Modeling
Authors: Drasbæk Daniel , Kungas Rainer , Blennow Peter , Heiredal-Clausen Thomas , Høgh Jens V. T. , Hauch Anne
Published: July 2021

Electrochemical impedance spectroscopy (EIS) is a powerful diagnostic tool for analyzing solid oxide electrolysis cells (SOECs). While EIS measurements on single-cell level are commonplace, implementation of EIS on stack level remains limited. Here, we report a framework for analyzing stack-level EIS data. Analysis of the collected impedance data comprises Kramers-Kronig transformations, distribution of relaxation times (DRT), and analysis of the difference of impedance spectra (ADIS). The DRT and ADIS results were used as input parameters for the complex non-linear least squares (CNLS) fitting procedure and the validity of the chosen equivalent circuit model was confirmed by reconstruction of Nyquist-, Bode-, DRT-plots, and the individual electrochemical contributions of the fitted data. The developed framework was successfully implemented on a commercial 75-cell SOEC stack (TSP-1) from Haldor Topsoe.
Experimental Investigation of Efficiency Maximization in Solid Oxide Electrolysis Systems by Internal Steam and Heat Recovery
Authors: Kruse Nicolas , Tiedemann Wilfried , Hoven Ingo , Deja Robert , Peters Roland , Blum Ludger , Peters Ralf
Published: July 2021

This study presents the development of a scalable steam generator for a reversible solid oxide cell system with 40 kW of power in electrolysis mode. As solid oxide electrolysis can be conducted under thermal-neutral conditions, efficiency is primarily governed by the system’s heat and steam loss. The steam generator presented herein recovers heat and steam from the fuel side off-gas in order to preheat the feed water and superheat the electrically-generated saturated steam. The design is based on a pinch analysis intended to optimize the temperature levels. In the considered system, the steam generator was estimated to increase electrolysis efficiency from 70% to more than 74%.
Development of Highly Efficient Composite Electrodes, CuFe2O4-La(Sr)Fe(Mn)O3, for High-Temperature Co-Electrolysis of CO2-Steam
Authors: Wu Kuan-Ting , Ishihara Tatsumi
Published: July 2021

La0.6Sr0.4Fe0.8Mn0.2O3-δ (LSFM) perovskite cathode has an advantage in product control for solid oxide electrolysis cell, while it limited by its insufficient electrolysis current density. To improve its electrochemical performance, we developed a highly efficient composite cathode by mixing LSFM with CuFe2O4 spinel. In this study, CO2/H2O co-electrolysis were investigated using CuFe2O4, LSFM, and their composites as cathodes on LaGaO3-based electrolyte. It was found that mixing LSFM and CuFe2O4 was effective for a significant increase in the electrolysis current density in co-electrolysis. Compared to the individual LSFM (0.60 A/cm2) and CuFe2O4 (1.00 A/cm2) cathode, a promising electrolysis current density of 1.43 A/cm2 was achieved at 1.6 V and 800oC with excellent Coulombic efficiency (> 95% of theoretical value), remarkable operation stability, and reversibility in co-electrolysis. In addition, a homogeneous and uniform surface morphology with a well-distributed porous structure was observed on the LSFM-CuFe2O4 composite layer after the operation.
Novel Composite Fuel Electrode for CH4-SOFC and CO2-SOEC
Authors: Duranti Leonardo , Luisetto Igor , D'Ottavi Cadia , Di Bartolomeo Elisabetta
Published: July 2021

The development of reversible solid oxide cells allows to use a single device to derive chemicals from power (power-to-fuel technology) and power from chemicals (fuel-to-power technology). We investigated a composite fuel electrode (60 wt.% La0.6Sr0.4Fe0.8Mn0.2O3-δ and 40 wt.% (5 wt.% Ni)-containing Ce0.58Sm0.15O2-δ) for dry methane oxidation in SOFC-mode and for CO2 reduction in SOEC-mode. In reducing conditions, Fe exsolved from the LSFMn perovskite formed a Ni-Fe alloy with Ni present on SDC. When tested as SOFC anode, the composite was active towards dry methane oxidation at 800°C and stable for over 40h; if tested as SOEC cathode, it showed remarkable activity for CO2 reduction. EIS analysis was used to have a better understanding of the cell mechanisms in SOFC and SOEC mode.
Changes in Microstructure of NiCo-Dispersed SDC Hydrogen Electrodes for the Improvement of Durability via Reversible Cycling Operation Between SOEC and SOFC-Modes
Authors: Uchida Hiroyuki , Nishino Hanako , Da'as Eman H.
Published: July 2021

We have examined changes in microstructure of double-layer hydrogen electrodes for solid oxide cells, consisting of a samaria-doped ceria (SDC) scaffold with highly dispersed Ni–Co nanoparticles as the catalyst layer (CL) and a thin current collecting layer of Ni–YSZ cermet, whose durability we recently found to undergo a remarkable improvement via reversible cycling operation between electrolysis and fuel cell-modes. The lower parts of many Ni‒Co particles were found to be anchored tightly on the SDC support after the cycling operation, probably due to a strong interaction between Ni‒Co and SDC. It was demonstrated by focused ion beam–scanning electron microscopy (FIB–SEM) that the Ni content in the CL was nearly fully maintained by the cycling operation, compared with a significant depletion of Ni after SOEC single-mode operation. Such a stabilization of the microstructure is proposed to contribute to the improved durability.
Co-Electrolysis of Simulated Coke Oven Gas with Carbon Dioxide Using a Solid Oxide Electrolysis Cell
Authors: Czachor Michal , Laycock Christian James , Carr Stephen , Maddy Jon , Lloyd Gareth , Guwy Alan
Published: July 2021

Coke oven gas (COG) is a byproduct of coke production typically composed of 57 vol% hydrogen, 27 vol% methane, 7 vol% carbon monoxide and impurities. It is partially re-utilised within steelmaking, with surplus flared and released to the atmosphere, significantly contributing to industrial carbon emissions and wasting a valuable resource. This study has investigated co-electrolysis of simulated COG (CH4/H2 mixtures) with a CO2 co-oxidant using a commercially available anode-supported solid oxide electrolysis cell at 750°C. The electrical performance of the cell was characterised using electrochemical techniques and the product gas composition was analysed using quadrupole mass spectrometry. With a 1:1 fuel-to-oxidant ratio, catalytic processes accounted for 68% of synthesis gas production, and a further 14% gain was achieved when operating in electrolysis mode at 1.4 V. H2/CO ratios of 1.1-2.4 were obtained depending on the fuel-to-oxidant ratio of the feed. Decreasing the fuel-to-oxidant ratio improved the electrical performance and durability of the cell but decreased the overall synthesis gas yield.
Spatial Current and Temperature Variations in a Microtubular Solid Oxide Electrolysis Cell In-Situ Analyzed with Electrode-Segmentation Method
Authors: Xuefeng Wang , Nakajima Hironori , Ito Kohei
Published: July 2021

The spatial distribution of current and temperature plays important role in the electrochemical performance of Solid Oxide Electrolysis Cells (SOECs). Many numerical predictions of current and temperature distribution have been reported, whereas experimental investigations were rare. In this research, we are applying an electrode-segmentation method to investigate the spatial current and temperature variation in a cathode-supported microtubular SOEC. The electrode-segmentation method shows a remarkable current variation among the segments. The current densities of the midstream and downstream segments are smaller than the upstream segment with an increased cell voltage, implying that the cell suffers from water starvation. Besides, the temperature at each segment increases with the voltage increase. The largest current in the upstream segment is observed, which agrees with the largest temperature rise there. The largest temperature gradient happens between the upstream and midstream segments.
Simulation and Analysis of Thermal Stress and Sintering Warpage of Planar Solid Oxide Fuel Cells
Authors: Lang Shaocheng , Zhang Jihao , Wu Mingtao , Zheng Jianmin , Zhao Xin , Xiao Liusheng , Sun Zaihong , Han Minfang , Yuan Jinliang
Published: July 2021

Due to mismatching of thermophysical properties between involved materials, a non-uniform distribution of generated thermal stress may result in a deformation and warpage in the cell sintering steps for SOFC (solid oxide fuel cell). A three-dimensional CFD (computational fluid dynamics) model is developed to study the displacement and thermal stress distribution within the SOFC sintered functional layers. It is found that the thermal stress is concentrated on the interface between the anode and the electrolyte layers; the warpage is larger during the co-sintering of anode and electrolyte layers (i.e., half-cell sintering). A parameter study is also conducted for the thickness variation of the anode, as well as for the four corners being chamfered. Considering effects of microscopic structure evolution on the cell shrinkage, a correlated method is developed to evaluate the thermal expansion coefficients varied with the sintering temperature. It is found that the difference becomes bigger in the correlated thermal expansion coefficients between the YSZ and anode layers, which leads to even larger displacement predictions. The findings and predicted results may be applied for optimization of the material designs and the sintering parameters for SOFC.
A Simplified Model for Reversible Solid Oxide Fuel Cells
Authors: Sezer Hayri , Mason Jerry H , Celik Ismail Bektas , Fan Yueying , Abernathy Harry W. , Epting William K , Kalapos Thomas , Hackett Gregory A
Published: July 2021

A simplified reversible steady-state solid oxide cell model is formulated and solved analytically with only a few calibration parameters to match experimental performance data. A Butler-Volmer type model is used for the hydrogen electrode while a two-step single pathway reduced-order oxygen reduction reaction model is applied in the oxygen electrode. It is shown that this simple model is capable of accurately predicting the trends of V-I data produced experimentally at various gas concentrations in both fuel cell and electrolysis modes.
Effects of Flow Channel Arrangement and Electrolyte Thickness on Thermal Stress for Planar Solid Oxide Fuel Cell Stacks
Authors: Zheng Jianmin , Xiao Liusheng , Chen Ming , Yuan Jinliang
Published: July 2021

Typical operating temperature for a solid oxide fuel cell (SOFC) ranges from 700°C to 800°C. A large temperature gradient and thermal stress are induced by internal losses and electro-chemical reactions, resulting in significant structural damage and performance degradation of a SOFC stack, which has become a hindrance to its applications. In this study, a three-dimensional multi-physics CFD model is developed and employed to study the temperature and thermal stress distribution of a planar SOFC stack, then effects of the structure design parameters are investigated, including the flow channel arrangement (i.e., co- and cross-flow) and thickness of the electrolyte layer. The stack modeled is composed of three-unit cells, metallic interconnect layers, sealing components, and anode/cathode current collectors. The simulation results show that the temperature difference in the co-flow case is smaller and the thermal stress is lower than those predicted in the cross-flow. The overall performance of the stack improves as the thickness of the electrolyte layer decreases, but the temperature and its gradient inside the stack become higher. In addition, a large temperature gradient is observed inside the thin electrolyte layer, which leads to a significant increase of the thermal stress. The findings and the research methods in this study can be applied to design and optimize the stack structures by considering the temperature and the thermal stress distribution.
Modeling of Multi-Physics Phenomena for High-Temperature Co-Electrolysis
Authors: Nohl Markus , Mazumder Jenifar , Vinke I. C. , Eichel Rüdiger-A. , de Haart L. G. J.
Published: July 2021

Solid Oxide Electrolysis Cells (SOEC) are on the rise and can usher in the energy transition. Storage of renewably supplied energy using P2X technologies enables on-demand retrieval of energy but also supply to various sectors. High temperature co-electrolysis of H2O and CO2 is a process capable of de-fossilizing the production of syngas, which can be integrated in future renewable P2X-scenarios. To describe the fundamentals of the co-electrolysis process, a theoretical model considering thermodynamics, kinetics, heat transfer, chemistry, and diffusion processes occurring together at the same time in the cell as well as the material properties of the respective layers, was developed. The boundaries are set with only steam and only CO2 electrolysis where the model is verified by matching calculated IV-characteristics with experimental ones. Comparing with experimental data, the activation loss is not dominating at low current densities. The reaction system is kept simple in order to account for the most probable rate-limiting step.
Design Optimization of a Thermally Integrated Solid Oxide Fuel Cell with Triple Effect Absorption Chiller
Authors: Lavernia Alejandro Carlos , Asghari Maryam , Mastropasqua Luca , Brouwer Jack
Published: July 2021

The integration of a solid-oxide fuel cell (SOFC) and a triple-effect absorption chiller (AC) is proposed to meet the electrical and cooling requirements of a data center. Utilizing waste heat in the exhaust stream of the SOFC, a triple-effect AC system can produce the required cooling. A 200-kW SOFC system is optimized to produce the required electricity at the maximum efficiency, while still producing enough thermal energy to run the 200-kW AC system. Similarly, the AC system is optimized to harness as much thermal energy from the SOFC as possible while meeting the cooling demand of the servers. The optimized system can meet both the electric and cooling demands to produce primary energy savings of 25.8%.
Anode-Oxidizing Critical Operating Conditions of Large Planar Solid Oxide Fuel Cell
Authors: Li Hangyue , Cui Tonghui , Han Minfang
Published: July 2021

Anode oxidation is a damaging fault in SOFC that may happen at high fuel utilization. To avoid anode oxidation, a 1D polarization and impedance model was developed for large planar SOFC, in order to reveal the critical operating condition. The model was validated with both experimentally measured j-V curve and impedance. The overpotential and impedance at each locality of the planar cell is predicted by a lumped-parameter model calibrated with button cell experimental data, with an RMS relative voltage error of 2.3%. The predicted operating voltage of a planar cell at given total current agrees well with measured data, with an RMS relative voltage error of 3.0%. At 750°C, the critical operating voltage increases up to 0.73 V as the fuel flow rate decreases. Further work is ongoing on a 2D spatially resolved model accounting for temperature distribution for more accurate prediction of anode-oxidizing operating conditions.
Numerical Study on Biogas Refining System Combined with Proton-Conducting Solid Oxide Electrolyzer
Authors: Tachikawa Yuya , Matsuzaki Yoshio , Kawabata Yasuharu , Taniguchi Shunsuke , Sasaki Kazunari
Published: July 2021

Biogas refining system including methanation reactor and proton-conducting electrolysis cell has been proposed and investigated based on the simulation including mass and heat balance analysis. Based on the calculation results, carbon deposition was predicted to still occur at the cathode outlet even with the gas humidification when a conventional oxide-ion conducting electrolyte is applied to the electrolysis cell due to the enhanced carbon activity caused by oxide-ion transport from the cathode to the anode. In the case of the proton-conducting electrolyte applied solid oxide electrolysis cell, proton transport from the anode to the cathode was found to mainly promote reverse water-gas shift reaction and methanation reaction without any carbon deposition. Even though the calculation results should be verified by comparing with experimental results, the numerical study suggested that the biogas refining system combined with p-SOEC is a promising technology for generating carbon-neutral methane with a strongly suppressed risk of carbon deposition.
Numerical Model of Co-Electrolysis in Solid Oxide Cells with Ni/Gd-Doped Ceria (CGO) Fuel Electrode
Authors: Koksharov Andrey , Taubmann Julian , Riegraf Matthias , Costa Rémi , Latz Arnulf , Jahnke Thomas
Published: July 2021

The co-electrolysis of atmospheric carbon dioxide with steam is seen as a potential source of synthesis gas. The electrochemically active elec-trode area on Ni/Gadolinium-doped ceria (CGO) electrodes extends from triple phase boundary (TPB) between Ni, CGO, and gas to the double phase boundary (DPB) between CGO and gas. The proposed numerical model of a commercial electrolyser cell aims to reveal main kinetic mechanisms responsible for the electro-reduction at the Ni/CGO fuel electrode. In order to identify main reaction pathways, electrochemical experiments with two types of fuel electrode were performed: porous CGO and mixed Ni/CGO electrode. In this work preliminary results for a mechanism explaining steam electrolysis at the Ni/CGO electrode are presented.
A Transient Three-Dimensional Mathematical Model for the Local Impedance and Polarization Performance of Planar SOFCs
Authors: Sezer Hayri , Mason Jerry H , Celik Ismail Bektas , Abernathy Harry W. , Epting William K , Kalapos Thomas , Hackett Gregory A
Published: July 2021

In the present work, a transient three-dimensional multi-physics model is used to predict the impedance and polarization behavior of a planar solid oxide fuel cell (SOFC) utilizing hydrogen under varying operation conditions and flow configurations. The mathematical model solves for species, charge, momentum, and energy transport in the cell components and interconnects. The mathematical model presented in this work is used to investigate the local impedance spectra and the current density distribution in different regions of the cell. The polarization and impedance simulations are performed for the full 3D domain and locally by dividing the cell into three regions along the flow direction. Parametric studies on key operating conditions such as fuel utilization, air utilization, gas flow rates, and composition are performed and the relative contributions to the polarization resistance of each parameter are quantified.
Leveling Transient and Spatial Gradients in Planar Solid Oxide Cells Using Spatially Varied Microstructures: A Numerical Study
Authors: Mason Jerry Hunter , Sezer Hayri , Celik Ismail Bektas , Abernathy Harry W. , Epting William K , Kalapos Thomas , Hackett Gregory A
Published: July 2021

Spatial and transient gradients of temperature, current density, and gas species concentrations are expected to occur within large area planar solid oxide cells. These gradients can be detrimental to cell performance and stability. Such gradients are inherent to the geometry of the flow fields and interconnects between cells, especially at high current densities and fuel/steam utilizations in fuel cell/electrolysis modes, respectively. To reduce the extent of these gradients, additive manufacturing techniques could be employed to level the electrochemical reaction rates in the electrodes by purposefully designing the electrode active layer to have engineered property distributions. The purpose of this study is to investigate the effects of applied microstructural property gradients on spatial and transient gradients under extreme operating conditions. Modeling results suggest that by strategically varying the volume fractions of composite electrode materials, it is possible to modulate temperature, species, and current density gradients in planar solid oxide cells.
Thermo-Mechanically Coupled Peridynamic Modelling of Fracture Formation in Solid Oxide Fuel Cell Anode
Authors: Xiang Yu , Zhong Zheng , Jiao Zhenjun
Published: July 2021

Fracture formation can be observed in brittle yttria-stabilized zirconia in Ni-YSZ composite anode during high-temperature operation of solid oxide fuel cells. It is difficult to predict the fracture formation in brittle solid materials accurately based on the classical continuum mechanics theory because of the singularity problems in partial differential equations. An ordinary state-based-peridynamic model is proposed to predict the fracture formation under external loads in SOFC anode in micro-scale using focused ion beam-scanning electron microscopy dual-beam technique in this work. The thermo-mechanical coupling effect is also investigated by simulating the formation and propagation of macro-scale crack in single cell under thermal shock.
Identification of Degradation Parameters in SOC Using In-Situ and Ex-Situ Approaches
Authors: Padinjarethil Aiswarya , Hagen Anke
Published: July 2021

Recent SOC activities focus on upscaling the applications to MW scales with target operation of several 10,000 hours. These long lifetimes require new approaches for durability testing. In the present study, the influence of different operating parameters on degradation was studied by long-term cell testing (in-situ treatment). Based on the results, accelerating parameters for ex-situ treatment were identified, which is a cheaper and time saving approach as compared to conventional cell/stack long-term testing. Two commercial SOC cell designs were studied: Anode supported cells (ASC) and Electrolyte supported cells (ESC).
Effect of Anode Side Purge Gas on the Degradation of Solid Oxide Electrolysis Cells
Authors: Sun Xiufu , Hendriksen Peter Vang , Hauch Anne , Clausen Anders Kring , Lehtinen Timo , Noponen Matti
Published: July 2021

In this work, the effect of purge gas supplied to the cell anode on the degradation of solid oxide electrolysis cells was studied. Three cells have been operated at 700 °C, -0.5 A/cm2 with 10% H2 + 90% H2O supplied to the fuel electrode compartment (cathode). The oxygen electrode was supplied either with air, CO2, or no gas. Detailed electrochemical characterization measurements, such as current-voltage curves and electrochemical impedance spectra, were obtained to monitor the cell degradation with time. The results show similar voltage after 1000 hr for the cells operated with air (1336 mV) and no purge gas (1370 mV), but a significantly higher voltage (1605 mV) for the CO2 purge. This cannot be explained by Nernst effects. Analysis of the cell impedance reveals that the oxygen electrode impedance is increased in CO2. The electrode performance partly recovers when terminating the CO2 purge.
Fracture of Porous Ceramics: Application to the Mechanical Degradation of Solid Oxide Cell During Redox Cycling
Authors: Abaza Amira , Meille Sylvain , Nakajo Arata , Leguillon Dominique , Hubert Maxime , Lenser C. , Laurencin Jérôme
Published: July 2021

A model based on the Phase Field approach has been developed to simulate the local fracture in porous electrode microstructures. The model capacity to predict the crack nucleation and propagation has been studied with theoretical considerations. For the model validation, micro-compression tests have been performed on porous YSZ micro-pillars. As expected, the compressive fracture strength has been found to decrease with the material porosity. Moreover, a transition in fracture mode has been detected from a brittle behavior toward a local damage when increasing the porosity. It has been shown that the model is able to reproduce correctly the experimental results. The validated model has been used to simulate the fracture of the YSZ backbone induced by the Ni re-oxidation in a typical Ni-YSZ cermet. The generation and localization of the micro-cracks have been discussed according to the degree of Ni re-oxidation and the local morphology of the electrode microstructure.
Local Characterization of a Solid Oxide Cell Operated in Fuel Cell and Electrolysis Mode Using Lock-in Thermography
Authors: Jeanmonod Guillaume , Van Herle Jan
Published: July 2021

Operando characterization of solid oxide cells (SOCs) generally relies on current–voltage measurements that provide the spatially averaged electrochemical response of the SOC. However, these methods do not fully capture the spatial distribution of the operating conditions (e.g., gas composition). To overcome this limitation, lock-in thermography was used to investigate the local electro-thermal behavior of an SOC operated in fuel cell and electrolysis mode. The SOC is stimulated with a sinusoidal current perturbation and the local thermal response analyzed using Fourier transforms. A compact data set is obtained that can be represented by a phase–amplitude or a real–imaginary image, the latter of which offers a better contrast. Here, the local thermal response depended on the current bias and the frequency of the perturbation. The thermal response was laterally and longitudinally inhomogeneous, thereby demonstrating the capability of active thermography to characterize the local behavior of an SOC in operando.
Comparison of Residual Stress Measurement Methods in Solid Oxide Fuel Cell
Authors: Oshima Kento , Komaya Takumi , Yashiro Keiji , Iguchi Fumitada , Han Minfang , Wang Yige , Kawada Tatsuya
Published: July 2021

We performed in-situ measurement of residual stress in an anode-supported cell using sin2
ψ method, cosα method, and Raman scattering spectroscopy. Residual stress at room temperature was evaluated by the sin2
ψ method, cosα method, and simulation. The stress values were generally consistent among the methods, with YSZ having a compressive stress of around 600 MPa. Residual stress analysis at high temperatures was attempted using Raman scattering spectroscopy which, however, was difficult to be applied above 700˚C. Instead, cosα method was successfully utilized for the measurement of residual stress during the temperature rise, reduction, and re-oxidation processes. The stress on the electrolyte observed during reduction and re-oxidation was different from that expected with a simple assumption of layered homogeneous sheets. These results showed that the cosα method is the most suitable method for in-situ measurements to validate simulated stress states.
Initial-Stage Performance Evolution of Solid Oxide Fuel Cells Based on Polarization Analysis
Authors: Wang Yige , Lyu Zewei , Han Minfang , Sun Zaihong , Sun Kaihua
Published: July 2021

The performance evolution of solid oxide fuel cells (SOFCs) is more pronounced and non-linear in the initial stage, determining the output level during subsequent long-term operation. In this study, an industrial-size (10×10 cm2) cell was tested under 0.1 A cm-2 for 96 hours. I-V-P curves and EIS data under different DC bias (0, 0.05, 0.10, 0.30, 0.50, 0.70 A cm-2) were periodically recorded every 24 hours to investigate the mechanism of initial-stage performance evolution. The ohmic loss was identified as the main contributor to the total overpotential, especially under large current density. The cell performance increased during 4-24 h due to the enhancement of anode gas-phase diffusion/conversion processes, while the performance degraded significantly during 48-96 h caused by the deterioration of anode charge transfer reaction. The EIS evolution trend under different DC bias was consistent, while the evolution degree was larger under smaller current density.
Performance Evolution of Ni-YSZ Anode-Supported SOFCs During Initial-Stage Operation
Authors: Lyu Zewei , Han Minfang
Published: July 2021

Performance evolution of typical Ni-YSZ anode-supported SOFCs during the initial-stage operation (<100 h) under different electrical currents is systematically evaluated. It is found that the performance evolution can be roughly divided into two stages, namely activation stage (about 0-20 h) and aging stage (> 20 h), regardless of the operating current. In the activation stage, the cell performance maintains stable or slightly increases due to the enhanced anode gas-phase diffusion. While in the subsequent aging stage, the cell performance decreases significantly and gradually approaches a plateau in about 100 hours, mainly due to the weakened anode charge transfer reaction and ionic transport processes. Therefore, it is suggested that more efforts should be focused on improving the stability of anode microstructure, especially the stability of anode functional layer.
Visualizing the Atomic Structure Between YSZ and LSM: An Interface Stabilized by Complexions?
Authors: Götsch Thomas , Tuerk Hanna , Schmidt Franz-Philipp , Vinke I. C. , De Haart L. G. J. (Bert) , Schlögl Robert , Reuter Karsten , Eichel Rüdiger-A. , Knop-Gericke Axel , Scheurer Christoph , Lunkenbein Thomas
Published: July 2021

The YSZ/LSM electrolyte/electrode interface of a half cell is investigated using electron microscopic and theoretical techniques. It is found that, due to strong interdiffusion of all cations except for Sr across the phase boundary, a so-called complexion is formed on the YSZ-side of the interface. This complexion is thermodynamically stabilized by the neighboring bulk phases and its consequences on activity and stability of SOCs are further discussed.
Electrochemical Reaction Mechanism of LSM-YSZ Composite Cathode Based on 3D Simulation of Oxygen Diffusion and Oxygen Labeling Experiment
Authors: Shimura Takaaki , Nagasawa Tsuyoshi , Shikazono Naoki , Hanamura Katsunori
Published: July 2021

Electrochemical reaction mechanism of an LSM-YSZ composite cathode is investigated using a combined measurement of oxygen labeling experiment and 3D numerical simulation using a reconstructed microstructure. First, an oxygen labeling experiment was conducted using 18O2 at 750°C under polarized condition. Then, a three-dimensional microstructure was obtained using a focused ion beam-scanning electron microscopy (FIB-SEM). Secondary ion mass spectroscopy (SIMS) analysis was conducted at the middle plane of the measured volume to correlate 18O distribution with the 3D microstructure. Using the 3D microstructure, electrochemical simulation was carried out considering the oxygen potential dependence of LSM ionic conductivity. Then, 18O transport was solved considering the balance between diffusion by concentration gradient, ionic current transport, and production by reaction current. The electrochemical reaction mechanism was discussed by comparing the numerically solved 18O concentration with that obtained from oxygen labeling experiment.
Sr and Co Vapor-Phase Transport from LSCF Cathodes
Authors: Kirby Brent , Hardy John S , Coyle Christopher , Canfield Nathan L , Droubay Tim
Published: July 2021

A series of tests were performed to differentiate between surface diffusion and vapor-phase diffusion of chemical species from LSCF cathode material at typical sintering temperatures (up to 1100°C) in SOFC production. A GDC source substrate was printed with LSCF and separated by an air gap from a YSZ target substrate. Various geometries with long surface paths were employed to reduce the possibility of surface transport. Sr and Co were detected on the target substrates via energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), including spatially resolved XPS. These results support a vapor-phase transport mechanism for Sr and Co. Sintering conditions and barrier layer requirements may need to be revisited to prevent the formation of undesired strontium zirconate at cathode/electrolyte interface due to vapor-phase transport.
PrBaCo2O5+δ-Sm0.5Sr0.5CoO3 Composite Oxide as Active Cathode for Intermediate-Temperature Solid Oxide Fuel Cells
Authors: Ishihara Tatsumi , Islamiyah Syuaibatul , Kluczny Maksymilian , Song Jun Tae , Takagaki Atsushi
Published: July 2021

Cathodic performance of double perovskite oxide of PrBaCo2O5 as an active catalyst for SOFC was investigated. Because delamination of PrBaCo2O5 cathode is easily occurred by larger thermal expansion coefficient, mixing effects of PrBaCo2O5 with another perovskite oxide were investigated using a LaGaO3-based electrolyte. Among the oxides mixed with PrBaCo2O5 (PBCO), it was found that mixing Sm0.5Sr0.5CoO3 (SSC) with PBCO shows the smallest cathodic overpotential and the most suitable for increase in cathodic activity. Increase in cathodic performance can be assigned to the high activity of oxygen dissociation on SSC and the fast oxide ion diffusivity in PBCO. Therefore, composite oxide of PBCO with SSC is highly active as cathode for SOFC at intermediate temperature.
Influence of the Ti Content on the Electrochemical Performance and Surface Properties of (La0.6Sr0.4)0.99Co1−
xTixO3−

δ
Oxygen Electrode
Authors: Heinsaar Alar , Kivi Indrek , Moeller Prit , Kooser Kuno , Käämbre Tanel , Aruväli Jaan , Lust Enn , Nurk Gunnar
Published: July 2021

(La0.6Sr0.4)0.99CoO3
-

δ
oxygen electrode material is a very promising oxygen electrode material due to its excellent electron and ionic conductivity. However, when using non-artificial air from the ambient atmosphere, it contains impurities such as H2O and CO2. These chemicals increase the degradation rate of the oxygen electrode. Introducing Ti into the B-site of (La0.6Sr0.4)0.99CoO3
-

δ
B-site increases the chemical stability of this oxygen electrode material. Synthesized and fabricated (La0.6Sr0.4)0.99Co1
-
xTixO3
-

δ
(0 ≤ x ≥ 0.1) electrodes and half cells were analyzed using X-ray diffraction method (XRD), X-ray photoelectron spectroscopy (XPS), and with electrochemical impedance spectroscopy (EIS). Results indicate that doping of (La0.6Sr0.4)0.99CoO3
-

δ
B-site with Ti makes this material more resilient to form unwanted compounds on the oxygen electrode surface.
Influence of Oxygen Partial Pressure on Cathodic Polarization of LaNiO3/GDC Composite Cathode
Authors: Namioka Tomoaki , Hirota Tomohisa , Hashimoto Shin-ichi , Itoh Hibiki
Published: July 2021

LaNiO3/GDC composite is one of the potential cathodic materials for intermediate temperature SOFCs. In order to assess its electrochemical performance, influence of oxygen partial pressure on cathodic polarization is examined with a LaNiO3/10GDC|10GDC|LaNiO3/10GDC symmetric cell by electrochemical impedance spectroscopy. The operating temperature was controlled from 773K to 1073K, and the partial pressure was controlled between −4 ≤ log(pO2/atm) ≤ 0 in this study. Polarization resistance increased with decreasing oxygen partial pressure at any temperature. In addition, the characteristic frequency (the summit frequency) of the impedance arc decreased with decreasing oxygen partial pressure. This implies that the rate determining step is changed by oxygen partial pressure. In practical operating condition: -1 ≤ log (pO2/atm), rate determining step is charge transfer reaction at 773 K and 873 K in this case.
First-Principle Study of Hole Localization in La1-XSrxFeO3-δ
Authors: Hartmann Cintia , Laurencin Jérôme , Geneste Grégory
Published: July 2021

Electronic structure calculations were carried out for La1-xSrxFeO3 at different strontium contents x (x=0.0, x~0.1, x~0.4, x~0.6). Progressive changes during Sr substitution were evaluated in the Density Of State (DOS) obtained from Density-Functional Theory +U calculations. The probability densities of the gap-state wave functions were visualized in order to describe the spatial extension of the localized electron holes. The oxygen vacancy formation energy was also determined. It was coupled to a defect model in order to give the concentration of oxygen vacancies and irons in different oxidation states at any temperature and oxygen partial pressure.
Performance and Stability of Nickelates Based Oxygen Electrodes for Solid Oxide Cells
Authors: Vibhu Vaibhav , Vinke I. C. , Eichel Rüdiger-A. , De Haart L. G. J. (Bert)
Published: July 2021

This work is focused on the development of alternative oxygen electrode materials for Solid Oxide Fuel Cells (SOFCs) and Solid Oxide Electrolysis Cells (SOECs). Rare earth nickelates with general formula Ln2NiO4+δ (Ln = La, Pr or Nd) have shown good performance as oxygen electrodes with various electrolytes. In order to further enhance the physico-chemical properties, electrochemical performance of these nickelates as oxygen electrode, we have performed the substitution of nickel by other transition element such as cobalt. Two compositions of Ln2Ni1-x
Co
x
O4+
δ (Ln = La, Pr, Nd) and La1.5Pr0.5Ni1-x
Co
x
O4+
δ (x=0.1 and 0.2) were mainly considered and completely characterized using several techniques. The single cells were then prepared and electrochemically characterized using DC- and AC-techniques in the temperature range 700-900°C. The stability tests up to 250 h were also investigated at ±1 A.cm-2 current density at 800°C under both SOFC (with 100% H2) and SOEC conditions (with 50% H2 and 50% H2O feed gas mixture) indicating different degradation behavior.
Interface Resistance of an SOFC Cathode with a Pr
1-X
Tb
x
O
2-D
Active Layer
Authors: Chiba Reiichi , Horie Kazuma , Kawaguchi Rin
Published: July 2021

We investigated the use of Pr1-XTbxO2-d (x=0.0-1.0) for use as the active layer material in an SOFC cathode. Pr1-XTbxO2-d (x=0.0-1.0) was successfully synthesized in a single-phase fluorite structure consisting of a solid solution of Pr6O11 and Tb4O7. When x was between 0.3 and 0.6, the phase transition between room temperature and 800oC was eliminated. Coin cells with GDC electrolyte, a Pr1-XTbxO2-d (x=0.0-1.0) active layer and a LaNi0.6Fe0.4O3 (LNF) current collecting layer were fabricated to clarify the effect of this active layer. The interface resistance of these cathodes was measured with an AC impedance method at 800oC. The cathodes with a Pr1-XTbxO2-d (all compositions) active layer performed better than that of a reference cathode, which has no active layer (simply an LNF layer).
Redox Durability of Ni-Co Alloy Cermet Anodes for SOFCs
Authors: Matsumoto Kohei , Tachikawa Yuya , Matsuda Junko , Taniguchi Shunsuke , Sasaki Kazunari
Published: July 2021

SOFCs are expected to be commonly used as a clean energy conversion technology. Ni-zirconia cermet, which is commonly used for SOFC anodes as an electronic conductor, has a problem that Ni agglomerates due to redox reactions disrupting the conductive path and leading to irreversible performance degradation. In this study, we fabricated anodes using Ni-Co alloy instead of Ni. By alloying Ni with Co, it was found that the same power generation performance and high redox cycle durability could be obtained.
Comparative Study of the Performance of Syngas-Fueled Carbon-Air Solid Oxide Fuel Cells Using Anodes Based on M-Doped CeO2 (M: Mo or Mo-Cu)
Authors: Diaz-Aburto Isaac , Colet Lagrille Melanie
Published: July 2021

A comparative analysis of difference in impedance spectra (ADIS) was performed for two SOFCs with different anode materials: CMO-YSZ and CMCuO-GDC, to determine the behavior of charge transfer and diffusive phenomena in both materials. This study showed a similar behavior for both materials, showing an increase of the diffusional limitations in the CMCuO-GDC anode with respect to the CMO-YSZ anode. The addition of copper reduced by 50% the total ohmic resistance of the cell with respect to the cell with CMO-YSZ anode, however, it was not possible to reduce the ASR value of the system. The maximum power densities obtained were 114 mW cm-2 and 120 mW cm-2 for the cells with CMO-YSZ and CuCMO-GDC anodes correspondingly, with CuCMO-GDC showing a slight increase in the electrocatalytic activity of the material.
Promotion of Hydrogen Oxidation and Methane Dry Reforming Over Ni-SDC Anode by Basic Oxide Additives
Authors: Kikuchi Ryuji , Mishina Tomohiro , Kayamori Taro , Fujiwara Naoya , Tada Shohei
Published: July 2021

Promoting effects of the additives such as MgO, CaO, BaO, and Cr2O3 to Ni-SDC (samarium-doped ceria) anodes were investigated on hydrogen oxidation and dry reforming of methane (DRM) activity. The additives were found to elevate current-voltage characteristics of H2-O2 fuel cells. The polarization resistance for H2 oxidation at the anodes was mainly decreased by the additives. The carbon balance in DRM reaction at open circuit voltage (OCV) approached 100% over the modified Ni-SDC anodes. The DRM activity was most promoted by the Cr2O3 additive, leading the highest OCV in direct DRM operation.