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Статті в журналах з теми "Ni-YSZ Fuel electrode":
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Vibhu, Vaibhav, Izaak Vinke, Rudiger-A. Eichel, and L. G. J. (Bert) de Haart. "Performance and Electrochemical Behavior of LSM Based Fuel Electrode Materials Under High Temperature Electrolysis Conditions." ECS Transactions 111, no. 6 (May 19, 2023): 1401–6. http://dx.doi.org/10.1149/11106.1401ecst.
Анотація:
Ni-YSZ is known as the state-of-the-art fuel electrode material for solid oxide cells. However, this conventional fuel electrode experiences severe degradation due to Ni- agglomeration and migration away from the electrolyte. Therefore, to avoid such issues, we have considered Ni free electrodes i.e. La0.6Sr0.4MnO3 (LSM) based perovskite oxides as fuel electrode. Under reducing atmosphere, the LSM perovskite phase transforms into a Ruddlesden-Popper (La0.6Sr0.4)2MnO4±δ phase. In addition to pure LSM fuel electrode, we have also investigated the performance of LSM+YSZ (50:50 wt %) and LSM+GDC (50:50 wt %) composite electrodes. The electrolyte-supported single cells were prepared using 8YSZ electrolyte supports, and in all cases, LSM+YSZ/LSM oxygen electrodes were used. The current-voltage characteristics show good performance for LSM and LSM+GDC fuel electrode containing single cells. However, a lower performance is observed for LSM+YSZ fuel electrode containing single cell. For instance, a current density of 997, 1025, and 511 mA.cm-2 at 1.5 V, are obtained for LSM, LSM+GDC, and LSM+YSZ fuel electrode containing single cells respectively, with 50% N2 and 50% H2O feed gas mixture.
2
Grimes, Jerren, Yubo Zhang, Dalton Cox, and Scott A. Barnett. "Enhancement of Ni-YSZ Fuel Electrode Performance Via Pressurization and GDC Infiltration." ECS Meeting Abstracts MA2023-01, no. 54 (August 28, 2023): 9. http://dx.doi.org/10.1149/ma2023-01549mtgabs.
Анотація:
Solid oxide cell systems are often designed for operation with a pressurized stack. Although the cell performance is expected to improve with pressurization, the details of how pressure affects the performance of various technologically-relevant electrodes are typically not known. Here we investigate the electrochemical characteristics of Ni-YSZ and GDC-infiltrated Ni-YSZ fuel electrodes in Ni-YSZ-supported cells as a function of total pressure P from 1 to 5 atm in H2/H2O fuel mixtures with humidification of 25%, 50%, and 75% and temperatures of 600˚C and 700˚C. Using electrochemical impedance spectroscopy, the two limiting electrode processes are identified: charge transfer reactions and gas diffusion. The charge transfer resistance is significantly reduced for Ni-YSZ:GDC compared to Ni-YSZ for all conditions, with total polarization resistance RP reduced by 30 - 40%. Fitting the data to a power-law dependence, RP ∝ P−n, yields a power law exponent of n = 0.28 for Ni-YSZ and 0.36 for Ni-YSZ:GDC (at 600˚C) and n = 0.32 for Ni-YSZ and 0.39 (at 700˚C). That is, GDC infiltration improved electrode performance more at higher pressure. Increasing the total pressure from 1 to 5 atm results in a 42% and 47% reduction in RP for infiltrated electrodes at 600˚C and 700˚C; these values are averaged for all humidities. Increasing humidity from 25 to 50% at 1 atm resulted in a ~26% reduction in total RP. The Ni-YSZ:GDC electrode at 5 atm had a RP value 63% - 65% lower than that of the Ni-YSZ electrode at 1 atm, a very substantial combined effect. The impact of pressurization on overall cell area-specific resistance is assessed based on the present data combined with prior measurements of oxygen electrode pressurization effects.
3
Ouyang, Zhufeng, Anna Sciazko, Yosuke Komatsu, Nishimura Katsuhiko, and Naoki Shikazono. "Effects of Transition Metal Elements on Ni Migration in Solid Oxide Cell Fuel Electrodes." ECS Transactions 111, no. 6 (May 19, 2023): 171–79. http://dx.doi.org/10.1149/11106.0171ecst.
Анотація:
In the present study, Ni-M (M = Fe, Cu) bimetallic fuel electrodes are applied to investigate the effects of transition metal elements on nickel (Ni) migration and Ni coarsening under SOFC and SOEC operations. Ni-Fe, Ni-Cu and pure Ni patterned fuel electrodes are sputtered on YSZ pellets. The electrochemical performance of these Ni-M bimetallic fuel electrodes are lower than pure Ni fuel electrode, while the degradation rate of Ni-Fe fuel electrodes is smaller than the others. The spreading of Ni film on YSZ surface is observed for all samples under anodic polarization, and such Ni migration is suppressed by Fe doping, whereas it was enhanced by Cu doping. The adhesion between the electrode/electrolyte interface is weakened for Ni-Cu and pure Ni fuel electrodes under cathodic polarization, while good adhesion at the interface is maintained for Ni-Fe, which correlates with the smaller performance degradation rate.
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Budiman, Riyan Achmad, Rikuto Konishi, Nanako Bisaka, Keiji Yashiro, and Tatsuya Kawada. "Time-Dependence of Microstructural Evolution and Performance Degradation of Ni/YSZ Electrode in Co-Electrolysis SOEC." ECS Meeting Abstracts MA2023-01, no. 54 (August 28, 2023): 231. http://dx.doi.org/10.1149/ma2023-0154231mtgabs.
Анотація:
Production of synthetic hydrocarbon fuels with Co-electrolysis using solid oxide electrolysis cell (SOEC) by Fischer-Tropsch reaction has attracted attention to solving energy and environmental problems. Reduction of CO2 and H2O to CO and H2 like a simple reaction process. However, carbon coking and microstructure alteration due to long-term operation could cause degradation performance, especially at Ni/YSZ fuel electrode. In this study, we determined the microstructure evolution and performance degradation of fuel electrode supported SOEC (Nexceris, USA) as function of temperature under 10% H2O:20%CO2 and applied voltage of -1.3 Volt. As a result, lower temperatures (1023 K) degradation showed faster degradation rate than higher temperatures (1073 K) despite similar fuel composition. Post-mortem analysis by SEM-EDX showed that the amount of carbon deposition is relatively low. However, the Ni average diameter increase by factor of two compared to as-reduced Ni/YSZ fuel electrode. Another measurement was conducted to confirm the effect of the water vapor only. It showed that the Ni average diameter was observed to be similar between co-electrolysis and water electrolysis conditions. This result indicated that the change of the Ni average diameter could be affected by the presence of water vapor only. There have been many reports on the change of Ni diameter in the Ni/YSZ for SOEC [1,2]. The Ni migration/diffusion in the Ni/YSZ fuel electrode is a complex mechanism, especially at the porous body because the complex geometry and morphology. Thus, it is so often to use model electrodes to simplify the geometry in order to understand the Ni migration [3]. The YSZ film was deposited on the MgO single crystal by pulsed-laser deposition (PLD). After that, the Ni film sputtered onto YSZ thin film, then patterned by photolithography. The Ni-pattern electrode can be viewed as a simplified cross-section of a porous electrode and simulated on a flat surface. It has two side Ni patterns in the opposite direction which are separated by a small gap on YSZ film which works as the electrolyte. At the edge of the Ni-pattern electrodes, the Pt electrodes were sputtered as a current collector. The model electrode was measured by applying a voltage on two-side of the Ni-patterned electrode where one Ni pattern was in fuel cell mode and another Ni pattern was in electrolysis mode. The measurement was completed under various gas composition at 1173 K. The measurement was taken every 20 h – 40 h before the laser microscope was used to observe the change in the Ni pattern electrode. The result on the model electrode will be corroborated with our study on Ni/YSZ porous. Acknowledgement This study was supported by the New Energy and Industrial Technology Development Organization (NEDO), Japan. Reference: [1] A. Hauch, S. D. Ebbesen, S. H. Jensen, M. Mogensen, J. Electrochem. Soc., 155(11) (2008) B1184-B1193. [2] D. The, S. Grieshammer, M. Schroeder, M. Martin, M. A. Daroukh, F. Tietz, J. Schefold, A. Brisse, J. Power Sources, 275 (2015) 901-911. [3] Z. Ouyang, Y. Komatsu, A. Sciazko, J. Onishi, K. Nishimura, N. Shikazono, J. Power Sources, 529 (2022) 231228.
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Ouyang, Zhufeng, Anna Sciazko, Yosuke Komatsu, Nishimura Katsuhiko, and Naoki Shikazono. "Effects of Transition Metal Elements on Ni Migration in Solid Oxide Cell Fuel Electrodes." ECS Meeting Abstracts MA2023-01, no. 54 (August 28, 2023): 28. http://dx.doi.org/10.1149/ma2023-015428mtgabs.
Анотація:
Solid oxide cells (SOCs), both solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC), have emerged and attracted more and more attentions due to its high energy conversion efficiency and fuel flexibility. However, degradation of fuel electrodes after long-term operation remains as one of the main challenges for their commercial application. Two major types of microstructure evolution, nickel (Ni) migration and Ni coarsening in Ni - yttria-stabilized zirconia (Ni-YSZ) fuel electrodes have been widely reported, which have strong impacts on both cell performance and durability. Therefore, materials-driven research has focused on developing more robust fuel electrodes with good electrocatalytic ability. Utilization of Ni alloys has immersed as a promising concept to enhance the performance and robustness of conventional Ni/YSZ. In the present study, Ni-M (M = Fe, Cu) bimetallic fuel electrodes are applied to investigate the effects of transition metal elements on the morphological evolutions under SOFC and SOEC operations. Ni-Fe, Ni-Cu and pure Ni patterned fuel electrodes are sputtered on YSZ pellets. The electrochemical performance of these Ni-M bimetallic fuel electrodes decreases compared with pure Ni fuel electrode, while the performance degradation rate of Ni-Fe fuel electrodes is smaller than others. Besides, the spreading of Ni film on YSZ surface is observed for all samples under anodic polarization and such Ni migration is suppressed by Fe doping, whereas enhanced by Cu doping. On the other hand, the adhesion is weakened at the electrode / electrolyte interface for Ni-Cu and pure Ni fuel electrodes under cathodic polarization, while good adhesion at the interface is maintained for Ni-Fe, which correlates with the smaller performance degradation rate.
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Kamboj, Vipin, and Chinmoy Ranjan. "Mixed Metal Cathodes for CO2 Electroreduction Using Solid Oxide Electrodes." ECS Meeting Abstracts MA2022-02, no. 64 (October 9, 2022): 2369. http://dx.doi.org/10.1149/ma2022-02642369mtgabs.
Анотація:
Electroreduction of CO2 to fuels through the use of renewable energy provides a beneficial route and it decreases the reliance on fossil fuels. The electrochemical reduction of CO2 to hydrocarbon fuels (CHx) is highly energy inefficient owing to kinetic limitations which are a direct consequence of multistep-multielectron transfer process. The selective formation of CO from CO2 is energy efficient. CO thus formed, serves as a valuable source of energy as it can be directly used as a fuel. Moreover, it can be further converted into hydrocarbon fuels via Fischer-Tropsch reactions using green hydrogen. We hereby propose Ni(M)x/YSZ based electrodes for electroreduction of CO2 on solid oxide cells at high temperature (~800∘C). Electrodes were fabricated on commercial standard YSZ supports using Ni(M)x/YSZ and LSM/YSZ mixtures which were respectively employed as materials for that cathode and anode. Characterisation of the developed electrode architecture was carried out via electron microscopy and X ray diffraction. The behaviour of electrodes during CO2 electrolysis was analysed through online mass spectrometry and operando Raman spectroscopy. Ni/YSZ electrodes displayed sustained performance only upon the addition of H2 to the fuel mixture. The reaction progressed through a reverse water gas shift reaction (RWGS) (CO2 + H2 à CO + H2O) along with water electrolysis where CO originates from non-electrochemical RWGS reaction. Electrochemical impedance spectroscopy was employed to analyse the reactions. Three electrode assembly was used to compare the electrochemical performance of the various electrodes. The pure Ni/YSZ cathodes showed deactivation under pure CO2 atmosphere. Mixed metal oxide electrodes such as Ni(M)x exhibit enhanced performance for CO2 electrolysis in both pure CO2 as well as in the presence of 5% H2. Catalytic performance of the electrodes was evaluated by varying fuel mixtures composition and temperature. Kinetics of electrode performance were evaluated using distribution of relaxation time formalism. Mixed metal oxide such as Ni(M)x showed improved kinetic with significant improvement in charge transfer resistance. Figure 1
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Ranjan, Chinmoy. "Mechanistic Details of CO2 Electroreduction on Ni and Ni{Cu}-YSZ Electrodes Using Operando Spectroscopy." ECS Meeting Abstracts MA2023-01, no. 54 (August 28, 2023): 13. http://dx.doi.org/10.1149/ma2023-015413mtgabs.
Анотація:
Electroreduction of CO2 to fuels using renewable energy can significantly help in reducing emissions and dependence of fossil fuels. Electrochemical reduction of CO2 to hydrocarbon fuels (CHx) is energy inefficient owing to multistep-multielectron transfer process which posses many kinetic limitations. The selective conversion of CO2 to CO is energy efficient. CO as product can be directly used as a fuel or converted to hydrocarbon fuels by using green hydrogen via Fischer-Tropsch reactions. Well known Ni/YSZ electrode architectures have both well-established lifetimes, performance benchmarks and optimised manufacturing protocols when it comes to use as SOFC. Unfortunately, using these electrodes as CO2 reduction electrodes requires use of H2 at the inlet. The reaction proceeds through a reverse water gas shift reaction (RWGS) (CO2 + H2 à CO + H2O) in conjunction with water electrolysis. Most of the CO originates from non-electrochemical RWGS reaction. Use of pure CO2 streams at currents exceeding 240mA/cm2 leads to catastrophic electrode failure. In the literature, it is believed that transformation of Ni metal to NiOx and carbon deposition via Bouduard reaction are the causes of electrode failure in pure CO2. We have adapted this well-known Ni/YSZ electrode by impregnation of Cu into the Ni architecture. The Ni{Cu}/YSZ electrode not only does not deactivate but also shows improved performance in every aspect compared to the pure Ni/YSZ electrode. We have developed a unique setup for operando Raman Spectroscopy and online mass spectroscopy which can be used to study electrode reactions under both steady state and transient conditions. Using this setup, we have shown that Ni-YSZ and Ni{Cu}/YSZ electrodes go through an oxide mediated mechanism of CO2 reduction. Metal oxides such as NiOx and Ni{Cu}Ox are the active catalyst species and not the metals. Upon applying strongly reducing conditions (currents > 240mA/cm2), NiOx reduces to Ni metal which can no longer catalyse the reaction, whereas the oxide on Ni{Cu}Ox is much stronger and does not reduce under even the most reducing of conditions (reducing currents >480mA/cm2). Such an electrode remains active for reducing pure CO2. Supporting studies using SEM, TEM, XPS, operando EIS, TPR and DFT modelling were also carried out. We believe that enabling CO2 reduction Ni/YSZ architecture using Cu impregnation is a game changer as all aspects of electrode manufacturing and device compatibility for Ni/YSZ have been extensively tested and market proven. This will allow for quick adaptation for this electrode in the CO2-SOEC market. Besides this, such a mechanistic study remains unique in the field of solid oxide-based research. Figure 1
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Mogensen, Mogens Bjerg, and Gurli Mogensen. "(Invited) On Degradation Mechanisms of Ni-YSZ Fuel Electrodes in Solid Oxide Cells." ECS Meeting Abstracts MA2023-02, no. 46 (December 22, 2023): 2236. http://dx.doi.org/10.1149/ma2023-02462236mtgabs.
Анотація:
The solid oxide cell (SOC) is reversible. It has about equally good performance both in solid oxide fuel cell (SOFC) and in solid oxide electrolyzer cell (SOEC) mode. The classical Ni-YSZ cermet SOC fuel electrode has an excellent initial performance provided that it has a good structure in terms of particle size of both Ni and YSZ, and a suitable porosity with sufficient contact between Ni-Ni, YSZ-Ni, YSZ-YSZ particles, and in absence of certain impurities such as silica and sulfur. The essential entity of the Ni-YSZ electrode is the length of the three phase boundary (3pb) between the three phases of Ni electron conductor, YSZ oxide ion conductor, and H2-H2O gas, which have electronic contact to the main Ni electrode, ionic contact to the bulk YSZ electrolyte, and access to the the main gas atmosphere, respectively. Nano-particular Ni is an excellent electrocatalyst for the reduction of H2O to H2 + O2- and for the oxidation. It seems that it is generally accepted that at operation temperatures (above 650 °C and above) the initial nano-sized Ni particles, which are in electric contact with each other, will over time continue to sinter into larger and larger Ni particles until all the Ni has become one dense body or the growth of the Ni particles has been blocked by particles of another phase like YSZ. Thus, the relative high mobility of Ni continues to pose a problem towards the lifetime of a highly functional Ni-YSZ electrode. A most serious type of degradation of Ni-YSZ electrodes in solid oxide electrolysis cells (SOEC) seems to be the one coupled to Ni-migration, which is regarded as an important obstacle for the commercialization of SOEC. Post mortem scanning electron microscopy investigations of the degraded Ni-YSZ electrode reveal that a thin (up to 3 – 5 µm) zone of the original nano-structured active Ni-YSZ cathode has been significantly been depleted in Ni. This degradation is clearly driven by the electrochemical polarization of the Ni-YSZ electrode [1], but the mechanism is highly discussed. Several researchers have the hypothesis that the Ni depletion is a result of Ni migration in a gradient in Ni/YSZ interface energy, see e.g. [2,3]. However, a review of relevant literature points out that this hypothesis cannot explain several reported clear experimental results, whereas our hypothesis based on Ni+ ions from Ni particles, which have lost electrochemical contact, migrate as NiOH across the YSZ particles to new active 3pbs formed further away from the bulk electrolyte. This hypothesis may qualitatively explain all reported results from steam electrolysis cells and H2 fuel cells so far [1]. However, our hypothesis does not directly explain the similar migration of Ni away from the YSZ bulk electrolyte in case of CO2 electrolysis. Therefore, a revision of our hypothesis will be presented. The essential change is simply to propose that it is the Ni+-ion that migrates in the YSZ-surface layer as either NiOH in case of steam electrolysis, or as “Ni2CO3” in case of CO2 electrolysis. A monolayer of “Ni2CO3” on a YSZ surface is not assumed to be any kind of crystalline Ni2CO3, but rather a layer of adsorbed Ni+ and “CO3 1-“ in which CO3 2- has one of its oxygen atoms incorporated into the YSZ surface crystalline structure which is formed by reaction between CO2 from gas and an unsaturated surface oxygen with a “dangling” electron with similarity to CO2 reduction on ceria [4]. Furthermore, the possible role of SiO2 impurities in the loss of contact between Ni and YSZ at negatively polarized Ni will be presented as another revision of the hypothesis together with further new details. References M.B. Mogensen et al., Fuel Cells, (2021), 1–15; DOI: 10.1002/fuce.202100072, and references therein. M. Trini et al., Acta Materialia, 212 (2021) 116887; DOI: 10.1016/j.actamat.2021.116887. L. Rorato et al., J. Electrochem. Soc., 170 (2023) 034504, DOI: 10.1149/1945-7111/acc1a3, and references therein. E.M. Sala et al., Phys. Chem. Chem. Phys. (2023), DOI: 10.1039/d2cp05157e.
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Kamboj, Vipin, and Chinmoy Ranjan. "Mixed Metal Ni(M)/YSZ for High-Temperature CO2 Electroreduction to CO." ECS Meeting Abstracts MA2022-01, no. 55 (July 7, 2022): 2312. http://dx.doi.org/10.1149/ma2022-01552312mtgabs.
Анотація:
Electroreduction of CO2 to fuels using renewable energy can significantly help in reducing emissions and dependence on fossil fuels. Electrochemical reduction of CO2 to hydrocarbon fuels (CHx) is energy inefficient owing to the multistep-multielectron transfer process, which possesses many kinetic limitations. The selective conversion of CO2 to CO is energy efficient. CO as product can be directly used as a fuel or converted to hydrocarbon fuels by using green hydrogen via Fischer-Tropsch reactions. We have used Ni(M)x/YSZ based electrodes to study electroreduction of CO2 on solid oxide cells at high temperature (~800∘C). Electrodes were developed on commercial standard YSZ supports using Ni(M)x/YSZ mixtures for cathode and LSM/YSZ mixtures for the anode. Electron microscopy and X-ray diffraction were used to characterize the electrode architecture and material. The electrodes were tested using online mass spectroscopy and operando Raman spectroscopy. Ni/YSZ electrodes showed sustained performance only when H2 was added to the fuel mixture, and the reaction proceeded through a reverse water gas shift reaction (RWGS) (CO2 + H2 → CO + H2O) in conjunction with water electrolysis with the CO originating from non-electrochemical RWGS reaction. The reactions were also analyzed using electrochemical impedance spectroscopy. The pure Ni/YSZ cathodes showed deactivation under a pure CO2 atmosphere with the formation of NiOx species with the catastrophic breakdown at high current densities around 400 mA/cm2. The behaviour could be verified using both mass spectroscopy and operando Raman Spectroscopy. The electrochemical performance of various electrodes was compared using a 3-electrode geometry. Mixed metal oxide electrodes such as Ni(M) showed improved kinetics, with significant improvement seen in the charge transfer resistance measured. Figure 1
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Grimes, Jerren, Yubo Zhang, Dalton Cox, and Scott A. Barnett. "Enhancement of Ni-YSZ Fuel Electrode Performance Via Pressurization and GDC Infiltration." ECS Transactions 111, no. 6 (May 19, 2023): 51–59. http://dx.doi.org/10.1149/11106.0051ecst.
Анотація:
Ni–(Y2O3)0.08(ZrO2)0.92 (YSZ) and Ce0.8Gd0.2O2 - δ (GDC) infiltratedNi-YSZ fuel electrodes are investigated using impedance spectroscopy as a function of total pressure P from 1 to 5 atm in 25%, 50%, and 75% humidified H2 mixtures at a temperature of 600˚C. The charge transfer resistance decreases significantly with infiltration for all conditions, and the total polarization resistance RP is reduced by ~20%. Fitting the P dependence to a power-law, RP ∝ P−n, yields an exponent of ~0.21 for both un-infiltrated and infiltrated tests. Increasing the total pressure from 1 to 5 atm results in an average 29% reduction in RP for both electrodes. Increasing the humidification from 25 to 75% generally results in a reduction in RP. The Ni-YSZ:GDC electrode at 5 atm had a RP value ~44% lower than that of the Ni-YSZ electrode at 1 atm, a substantial combined effect.
Дисертації з теми "Ni-YSZ Fuel electrode":
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Rorato, Léa. "Optimisation des électrodes de Ni-YSZ pour une meilleure stabilité des cellules à oxydes solides." Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALI013.
Анотація:
La durabilité des Cellules à Oxyde Solide reste l'un des principaux problèmes limitant le déploiement à grande échelle de cette technologie. La température de fonctionnement élevée (700°C-850°C) ainsi que la polarisation peuvent induire une réactivité entre les composants de la cellule ainsi qu’une évolution de la microstructure des électrodes, en particulier en mode électrolyse (SOEC). Plus précisément, le cermet de Ni-YSZ, classiquement utilisé comme électrode à hydrogène est soumis à un grossissement local du Ni et à une redistribution sur une grande distance. En effet, une migration substantielle du Ni loin de l'interface électrolyte/cermet est généralement observée en mode électrolyse. Inversement, seul un léger enrichissement en Ni de l'interface électrolyte/électrode est détecté après un temps long de fonctionnement en mode pile à combustible. Cependant, le mécanisme sous-jacent à l’origine de la migration du Ni, est peu ou mal compris et fait l’objet de nombreuses études internationales. Cette thèse a donc été consacrée à la compréhension du mécanisme de migration du Ni, en utilisant une approche couplée expérimentale et de modélisation. Premièrement, un mécanisme a été proposé pour la migration du Ni qui prend en compte l'évolution de la double couche électrochimique et la mouillabilité du Ni sur la YSZ avec la polarisation de l'électrode. De plus, une série de tests de longues durées a été menée afin d'étudier l'effet des différentes conditions de fonctionnement sur l'évolution de la microstructure du Ni, y compris la caractérisation de la microstructure post-test. Ensuite, un modèle basé sur le mécanisme proposé a été développé dans un code d’éléments finis (COMSOL®), utilisant la théorie des champs de phase pour la prédiction de l'évolution de la migration du Ni. Le modèle de champ de phase a initialement été validé sur une microstructure simplifiée avant d'être appliqué à une microstructure réelle. Il convient de noter que le gradient de mouillabilité Ni/YSZ imposé comme conditions limites dans le modèle de champ de phase a été calculé à l'aide d'un modèle électrochimique calibré pour reproduire le comportement des cellules utilisées dans le cadre de cette thèse. Des simulations en modes SOEC et SOFC dans les conditions des tests de durabilité (-/+1 A.cm-², 750°C), pour 2000h, ont été lancées puis les résultats ont été discutés à la lumière de la bibliographie et confrontés aux reconstructions expérimentales des électrodes. Finalement, la pertinence du mécanisme proposé a été confirmée par le bon accord entre les simulations et les données expérimentalesThe Solid Oxide Cells durability remains one of the main issue limiting the large-scale deployment of this technology. The high operating temperature (700°C-850°C) and polarization can induce reactivity between the cell components or microstructure evolution in the electrodes especially in electrolysis mode (SOEC). Specifically, the classical Ni-YSZ cermet used as hydrogen electrode is subjected to Ni local coarsening and redistribution over large distance. Indeed, a substantial Ni migration away from the electrolyte/cermet interface is generally observed in electrolysis mode. Conversely, only a slight Ni enrichment of the electrolyte/electrode interface is detected for long-term operation in fuel cell mode. However, the underlying mechanism for the Ni migration remains unclear. Therefore, this thesis has been dedicated to the understanding of the Ni-migration using a coupled experimental and modelling approach. For this purpose, a mechanism has been proposed for Ni migration that takes into account the evolution of the electrochemical double layer and the Ni wettability on YSZ, with the electrode polarization. Besides, a series of long-term tests have been conducting in order to investigate the effect of the different operating conditions on the evolution of the Ni microstructure including post-test microstructural characterization. Then, a model based on the proposed mechanism has been developed in a finite element code (COMSOL®) using the phase-field theory to predict the evolution of the Ni migration on real microstructures. The phase-field model has been first validated on a simplified microstructure before been applied to a real one. It is worth noting that the gradient in Ni/YSZ wettability imposed as boundary conditions in the phase-field model have been computed with an electrochemical model calibrated to reproduce the behaviour of the cells used in this work. Phase-field simulations in SOEC and SOFC modes in the conditions of the experiments for 2000h (-/+1 A/cm², 750°C) have been launched and the results discussed in the light of the bibliography and confronted to the experimental electrode reconstructions. The good agreement between the simulations and the experimental data tends to prove the relevance of the proposed mechanism
Тези доповідей конференцій з теми "Ni-YSZ Fuel electrode":
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Kim-Lohsoontorn, P., H. B. Yim, and J. M. Bae. "Electrochemical Performance of Ni-YSZ, Ni/Ru-GDC, LSM-YSZ, LSCF and LSF Electrodes for Solid Oxide Electrolysis Cells." In ASME 2010 8th International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2010. http://dx.doi.org/10.1115/fuelcell2010-33017.
Анотація:
The electrochemical performance of solid oxide electrolysis cells (SOECs) having nickel – yttria stabilized zirconia (Ni-YSZ) hydrogen electrode and a composite lanthanum strontium manganite – YSZ (La0.8Sr0.2MnO3−δ – YSZ) oxygen electrodes has been studied over a range of operating conditions temperature (700 to 900°C). Increasing temperature significantly increased electrochemical performance and hydrogen generation efficiency. Durability studies of the cell in electrolysis mode were made over 200 h periods (0.1 A/cm2, 800°C, and H2O/H2 = 70/30). The cell significantly degraded over the time (2.5 mV/h). Overpotentials of various SOEC electrodes were evaluated. Ni-YSZ as a hydrogen electrode exhibited higher activity in SOFC mode than SOEC mode while Ni/Ru-GDC presented symmetrical behavior between fuel cell and electrolysis mode and gave lower losses when compared to the Ni-YSZ electrode. All the oxygen electrodes gave higher activity for the cathodic reaction than the anodic reaction. Among the oxygen electrodes in this study, LSM-YSZ exhibited nearest to symmetrical behavior between cathodic and anodic reaction. Durability studies of the electrodes in electrolysis mode were made over 20–70 h periods. Performance degradations of the oxygen electrodes were observed (3.4, 12.6 and 17.6 mV/h for LSM-YSZ, LSCF and LSF, respectively). The Ni-YSZ hydrogen electrode exhibited rather stable performance while the performance of Ni/Ru-GDC decreased (3.4 mV/h) over the time. This was likely a result of the reduction of ceria component at high operating voltage.
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Sakamoto, Yusuke, Naoki Shikazono, and Nobuhide Kasagi. "Effects of Electrode Microstructure on Polarization Characteristics of SOFC Anodes." In ASME 2008 6th International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2008. http://dx.doi.org/10.1115/fuelcell2008-65079.
Анотація:
Anode microstructure parameters were quantified by SEM-EDX measurements and the dependence of polarization characteristics on the anode microstructure parameters is investigated experimentally. Nickel yttria-stabilized zirconia (Ni-YSZ) anode supported cells with a thin YSZ electrolyte, lanthanum-strontium-manganite (LSM)-YSZ composite cathode, and LSM cathode current collector layers were fabricated by dip coating method. Anode microstructure was successfully imaged and quantified by ultra low voltage SEM and by means of stereology. Cell voltage measurements and impedance spectroscopy were performed at 650 and 750°C with hydrogen diluted by nitrogen as a fuel. A quantitative relationship between measured polarization and microstructure parameters, e.g., three phase boundary length, contiguity, etc., was discussed. Finally, a cell with an anode functional layer (AFL) was fabricated to investigate the possibility of improving both activation and concentration polarization characteristics.
3
Martins, R. F., M. C. Brant, R. Z. Domingues, and T. Matencio. "NiO/YSZ Composites for SOFC: Synthesis and Characterization." In ASME 2006 4th International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2006. http://dx.doi.org/10.1115/fuelcell2006-97146.
Анотація:
Solid oxide fuel cell (SOFC) works at high temperature and is normally used in stationary devices which are of wide interest in the world market. The most currently SOFC developers utilize yttria-stabilized zirconia (YSZ) as electrolyte, strontium-doped lanthanum manganite (LSM) as cathode and a Ni/YSZ cermet obtained from NiO/YSZ in situ reduction as anode. The electrode performance is directly influenced by powder grain sizes, homogeneity, purity, and amount of Ni. Although physical mixture is a simpler procedure it hardly gives homogeneous materials as suitable to SOFC applications. Alternative chemical methods are sol-gel, impregnation and those derived from Pechini route. The present work compares thermal stability and hydrogen reducibility of NiO/YSZ composites prepared by impregnation (I), Pechini (P) and physical mixture (PM) procedures.
4
Ju, W. T., and S. H. Hong. "Development of Fabrication Processes for Tubular Solid Oxide Fuel Cell (SOFC) by Plasma Spraying." In ITSC 1998, edited by Christian Coddet. ASM International, 1998. http://dx.doi.org/10.31399/asm.cp.itsc1998p1067.
Анотація:
Abstract The atmospheric pressure plasma spray processes for functional layers of the tubular solid oxide fuel cell are developed to build a fuel cell structure consisting of air electrode, ceramic electrolyte, and fuel electrode. Further more the characteristics of each film are also investigated. The layers of LSM (La0.65Sr0.35MnO3) air electrode and Ni/8YSZ fuel electrode have porosities of 23 ~32 % sufficient for supplying fuel and oxidant gases efficiently to electrochemical reaction interfaces. The measured electrical conductivities of the electrodes are higher than 90 S/cm at 1000 °C, which satisfy the requirement as the current collecting electrodes. The YSZ electrolyte film has a high ionic conductivity of 0.07 S/cm at 1000 °C, but shows a bit too porous to block the oxygen molecule penetration through it. A unit tubular SOFC is fabricated by the optimized plasma spray processes for depositing each functional film and forming a porous cylindrical supporting tube of the cell, and turns out to have a promising capability of electricity generation.
5
Schiller, G., M. Müller, R. Ruckdäschel, R. Henne, and M. Lang. "Plasma Spraying of Solid Oxide Fuel Cell Components." In ITSC 1997, edited by C. C. Berndt. ASM International, 1997. http://dx.doi.org/10.31399/asm.cp.itsc1997p0027.
Анотація:
Abstract The central components for solid oxide fuel cells (SOFC) are the electrodes-electrolyte multilayer arrangement (PEN) and the separating bipolar plates. The PEN (Positive electrode- Electrolyte-Negative electrode) assembly consists of a dense gastight yttria-stabilized zirconia (YSZ) electrolyte and porous electrodes for which usually Ni-YSZ cermet anode and Sr-doped LaMnO3 cathode layers are used. The various PEN units are connected in a cell stack by bipolar plates which are either metallic or ceramic ones. Furthermore, a protective layer on the metallic bipolar plates consisting of a chromium alloy is required to prevent chromium evaporation leading to a rapid and strong degradation of the SOFC performance. At the DLR Stuttgart both the DC and the RF vacuum plasma spraying technique have been further developed and adapted to meet the requirements for the manufacture of the different SOFC components. The DCVPS process using specially developed Laval-like nozzles is especially appropriate to the production of thin and dense coatings as required for the electrolyte and the protective layers. However, applying special spray parameters and nozzles it is also possible to deposit porous electrode layers. The production of the entire PEN arrangement in one consecutive DC-VPS process is the objective of the actual development. On the other hand, the RF plasma spray technique is suitable for the near net-shape production of bulk components such as the metallic bipolar plate. The development of the deposition processes for the production of SOFC components using DC and RF plasma spray methods and the results obtained concerning PEN fabrication, deposition of protective layers and the near net-shape production of metallic bipolar plates are presented in the paper.
6
Maric, Radenka, Roberto Neagu, Ye Zhang-Steenwinkel, Frans P. F. van Berkel, and Bert Rietveld. "Flame Deposition of the Electrolyte and Cathode for High and Stable Performance of Low-Temperature SOFCs." In ASME 2010 8th International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2010. http://dx.doi.org/10.1115/fuelcell2010-33342.
Анотація:
The key obstacles to the development of low operating temperature (LT) SOFCs are high ohmic resistance and high electrode overpotentials. In the present work, we demonstrate excellent cell performance at 600 °C on a anode supported bi-layer electrolyte SOFC having a thin RSDT-made cerium gadolinium oxide (Gd0.2Ce0.8O2−δ, CGO) and a lanthanum strontium cobaltite (La0.6Sr0.4CoO3−δ, LSC) perovskite cathode. The measured ohmic resistance of the ASE cell with CGO layer deposited by RSDT was 0.24 ohm.cm2, which is close to the expected theoretical value of 0.17 ohm.cm2 for a 5 micron thick 8YSZ electrolyte at 600 °C. This indicates that the obtained peak power output density is approaching what is theoretically possible. This work is based on the lab scale use of Reactive Spray Deposition Technology (RSDT) which is an open atmosphere, cost efficient technique that does not require high vapor precursors and is an effective way to deposit thin ceramic layers of YSZ/CGO/LSC onto Ni-YSZ substrates. It has the potential to chain successive coating steps thus, significantly simplifying the production of multilayered ceramic structures as the SOFCs and reducing the cost associated with manufacturing of the cells.
7
Lanzini, Andrea, Pierluigi Leone, Marco Pieroni, Massimo Santarelli, Davide Beretta, and Stefano Ginocchio. "Experimental Investigation and Modeling of Direct Internal Reforming of Biogases in Tubular SOFC." In ASME 2010 8th International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2010. http://dx.doi.org/10.1115/fuelcell2010-33102.
Анотація:
Biogas-fed SOFC systems can be considered as interesting power systems in the framework of distributed generation plants. In particular, bio-methane (CH4/CO2 60/40 vol.) and bio-hydrogen (H2/CO2 50/50 vol.), produced from anaerobic digestion of wastes, represent renewable fuels for high efficiency electrochemical generators. This study investigates the behavior of an anode-supported (Ni-YSZ) tubular cell fed by the two fuels. The tubular geometry has been considered since it causes a complete separation of the electrodes reactants, allowing the analysis of the evolution of the fuel gas inside the tube, in terms of composition (consequence of electrochemical and heterogeneous chemical reactions) and temperature field. The experiments have been designed in order to analyse the behavior under different load and fuel utilization conditions. In particular, the fuel mixtures have been conditioned to avoid carbon build-up on the anode electrode. The experimental results have been then used to validate a 2D model (taking into account the cell axial symmetry) of the multi-physics phenomena occurring along the tubular cell. The model shows a good accordance with the experimental data, and has therefore been used to analyse the effects linked to the modification of some geometrical parameters of the tube in terms of performance of the cell.
8
Milcarek, Ryan J., and Jeongmin Ahn. "Micro-Tubular Flame-Assisted Fuel Cell Power Generation Running Propane and Butane." In ASME 2018 Power Conference collocated with the ASME 2018 12th International Conference on Energy Sustainability and the ASME 2018 Nuclear Forum. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/power2018-7175.
Анотація:
Direct use of propane and butane in Solid Oxide Fuel Cells (SOFCs) is desirable due to the availability of the fuel source, but is challenging due to carbon coking, particularly on the commercially available Ni+YSZ anode. A novel dual chamber Flame-assisted Fuel Cell (FFC) configuration with micro-tubular SOFCs (mT-SOFCs) is proposed for direct use of higher hydrocarbon fuels. Combustion exhaust for propane and butane fuels is analyzed experimentally and compared with chemical equilibrium. mT-SOFC polarization and power density testing in the FFC configuration with propane and butane fuels is discussed. Peak power and electrical efficiency conditions are assessed by varying the fuel-rich combustion equivalence ratio and flow rate. Carbon deposition and soot formation on the Ni+YSZ anode is investigated with a scanning electron microscope. The results indicate that reasonable power density (∼289 mW.cm−2) can be achieved while limiting soot formation in the flame and carbon deposition on the anode. Electrical efficiency based on the higher heating value of the fuels is analyzed and future research is recommended. Possible applications of the technology include small scale power generation, cogeneration and combined cycle power plants.
9
Rajaram, Gukan, Salil Desai, Zhigang Xu, Devdas M. Pai, and Jag Sankar. "Process Optimization Studies on Ni-YSZ Anode Material for Solid Oxide Fuel Cell Applications." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-43592.
Анотація:
The characteristics of the Ni/YSZ anode material for the solid oxide fuel cells (SOFCs) were investigated in order to study the relation between the porosity and the conductivity of the cell. The nano-sized Yittria Stabilized Zirconia (YSZ) (∼ 60 nm), Nickel Oxide (NiO) (∼ 40 nm) and graphite (∼ 40 nm) particles were used as the raw materials. The graphite particles act as a pore former. The experiments were planned based on a response surface design (central composite design matrix). The graphite content and the sintering temperatures were varied based on the design chart, while the other variables like NiO/YSZ ratio, ball milling time, powder compaction pressure and reduction temperature values were fixed. Porosity and conductivity measurements were performed on the sintered and reduced anode material. The results indicated that the porosity values got decreased by increasing sintering temperature values, while the conductivity values were on the reverse scale. The conductivity values increase with increasing temperature. The scanning electron microscope (SEM) images showed that the sintering temperature had a visible impact on the microstructure. At elevated temperature, the microstructure showed visible particle growth and it formed a better Ni-network along the structure, compared to samples sintered at lower temperature. It is believed that the enhanced Ni-network at elevated temperature helps to increase the electrical conductivity of the Ni-YSZ anode cermet.
10
Brus, Grzegorz, Zygmunt Kolenda, Shinji Kimijima, and Janusz S. Szmyd. "An Analysis of Heat Transfer Processes in an Internal Indirect Reforming Type Solid Oxide Fuel Cell." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22785.
Анотація:
This paper presents experimental and numerical studies on the fuel reforming process on an Ni/YSZ catalyst. Nickel is widely known as a catalyst material for Solid Oxide Fuel Cells. Because of its prices and catalytic properties, Ni is used in both electrodes and internal reforming reactors. However, using Ni as a catalyst carries some disadvantages. Carbon formation is a major problem during a methane/steam reforming reaction based on Ni catalysis. Carbon formation occurs between nickel and metal-support, creating fibers which damage the catalytic property of the reactor. To prevent carbon deposition, the steam-to-carbon ratio is kept between 3 and 5 throughout the entire process. To optimize the reforming reactors, detailed data about the entire reforming process is required. In the present paper kinetics of methane/steam reforming on the Ni/YSZ catalyst was experimentally investigated. Measurements including different thermal boundary conditions, the fuel flow rate and the steam-to-methane ratios were performed. The reforming rate equation derived from experimental data was used in the numerical model to predict synthetic gas composition at the outlet of the reformer.