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1.
A new phenomenological one‐dimensional model is formulated to simulate the typical degradation patterns observed in solid oxide fuel cell (SOFC) anodes due to coal syngas contaminants such as arsenic (As) and phosphorous (P). The model includes gas phase diffusion and surface diffusion within the anode and the adsorption reactions on the surface of the Ni‐YSZ‐based anode. Model parameters such as reaction rate constants for the adsorption reactions are obtained through indirect calibration to match the degradation rates reported in the literature for arsine (AsH3), phosphine (PH3), hydrogen sulfide (H2S), and hydrogen selenide (H2Se) under accelerated testing conditions. Results from the model demonstrate that the deposition of the impurity on the Ni catalyst starts near the fuel channel/anode interface and slowly moves toward the active anode/electrolyte interface as observed in the experiments. Parametric studies performed at different impurity concentrations and operating temperatures show that the coverage rate increases with increasing temperature and impurity concentration, as expected. The calibrated model was then used for prediction of the performance curves at different impurity concentrations and operating temperatures. Good agreement is obtained between the predicted results and the experimental data reported in the literature. 相似文献
2.
Ba0.5Sr0.5Co0.7In0.1Fe0.2O3−δ powders are successfully synthesized as the cathode materials for proton‐conducting solid oxide fuel cells (SOFCs). The prepared cells consisting of the structure of a BaZr0.1Ce0.7Y0.2O3−δ (BZCY7)‐NiO anode substrate, a BZCY7 electrolyte membrane and a cathode layer, are measured from 600 to 700 °C with humidified hydrogen (ca. 3% H2O) as the fuel. The electrochemical results show that the cell exhibits a high power density which could obtain an open‐circuit potential of 0.986 V and a maximum power density of 400.84 mW cm−2 at 700 °C. The polarization resistance measured at the open‐circuit condition is only 0.15 Ω cm2 at 700 °C. 相似文献
3.
Recently, the promising prospect of ammonia as a hydrogen carrier for solid oxide fuel cells (SOFCs) has attracted significant interests. In this work, the effects of temperature, fuel content, and total flow rate of anode gas on the performance of Ni/yttria‐stabilized zirconia (Ni/YSZ) anode for ammonia‐fueled SOFCs were investigated. Based on obtained results, the utilization route of ammonia on Ni/YSZ anode was discussed; the results of electrochemical experiments were related with the catalytic decomposition bahavior of ammonia over Ni/YSZ. Moreover, the catalytic activity for ammonia decomposition and anode performance of Ni/samarium‐doped ceria (Ni/SDC) and Ni/yttrium‐doped barium cerate (Ni/BCY) were also investigated. Among these anode materials, Ni/BCY exhibited the highest ammonia decomposition activity and anode performance for ammonia‐fueled SOFCs at intermediate temperatures. 相似文献
4.
L. dos Santos-Gómez J. Zamudio-García J.M. Porras-Vázquez E.R. Losilla D. Marrero-López 《Ceramics International》2018,44(5):4961-4966
La0.8Sr0.2MnO3-δ-Ce0.9Gd0.1O1.95 (LSM-CGO) nanostructured cathodes are successfully prepared in a single process by a chemical spray-pyrolysis deposition method. The cathode is composed of nanometric particles of approximately 15 nm of diameter, providing high triple-phase boundary sites for the oxygen reduction reactions. A low polarization resistance of 0.046 Ω cm2 is obtained at 700 °C, which is comparable to the most efficient cobaltite-based perovskite cathodes. A NiO-YSZ anode supported fuel cell with the nanostructured cathode generates a power output of 1.4 W cm?2 at 800 °C, significantly higher than 0.75 W cm?2 for a cell with conventional LSM-CGO cathode. The results suggest that this is a promising strategy to achieve high efficiency electrodes for Solid Oxide Fuel Cells in a single preparation step, simplifying notably the fabrication process compared to traditional methods. 相似文献
5.
T. Ramos S. Veltz B. R. Sudireddy P. S. Jrgensen L. Theil Kuhn P. Holtappels 《Fuel Cells》2014,14(6):1062-1065
Electrolyte supported cells (ESC), with Sc2O3‐stabilized ZrO2 (ScSZ) electrolytes, Gd‐doped ceria (CGO) or M/CGO (M = Ni, Ru) infiltrated Sr0.94Ti0.9Nb0.1O3 (STN94) anodes and LSM/YSZ cathodes, were evaluated for their initial performance and long‐term stability. Power density for the Ru/CGO infiltrated cell reached ∼0.7 W cm–2 at 850 °C, 4% H2O/H2, whereas the Ni/CGO infiltrated cell reached ∼0.3 W cm–2, with the current morphologies and loadings. Operation at 0.125 A cm–2, 850 °C, feeding 50% H2O/H2 to the anode and air to the cathode, for a period >300 h, showed superior stability for the Ru/CGO infiltrated cell, with ∼0.04 mV h–1 degradation rate, when compared to the Ni/CGO infiltrated cell (∼0.5 mV h–1). For the Ni/CGO case, the observed degradation has been tentatively linked to initial changes in the electrochemical active area and long‐term detrimental interactions between components. 相似文献
6.
A Ni/Yttria‐stabilized zirconia (YSZ) cell with a (La0.60Sr0.40)0.95Co0.20Fe0.80O3–δ cathode is tested both in fuel cell and electrolysis modes. In fuel cell mode under dry air and wet H2, the cell is operated between the open circuit voltage (OCV) and 0.4 V and reaches 330 mW cm−2 at 850 °C for 157 mL min−1 H2 supply. The influence of temperature and air or hydrogen flow rate is studied, and impedance measurements show that below 0.8 V the electrolyte becomes the more resistive part of the cell. Nevertheless, fuel utilization yields are higher under oxygen or hydrogen depletion. If it is possible at 750 °C to work at low voltage during several hours in the entire voltage range, the voltage decrease must be limited at 850 °C. The cell can also be operated under wet air. The same cell can be operated in electrolysis mode, and a power density of 340 mW cm−2 can be obtained at 0.3 V/OCV under 100 mL min−1 wet (3% H2O) 5% H2–95% Ar mixture on the fuel side and dry or wet 100 mL min−1 air flow on the air side. Nevertheless, bubbling air providing the air electrode in saltwater has an irreversible detrimental effect on the cell. 相似文献
7.
BaCe0.8Pr0.2O3 (BCP20) and BaCe0.6Pr0.4O3 (BCP40) powders are successfully synthesized through the Pechini method and used as the cathode materials for proton‐conducting solid state oxide fuel cells (SOFCs). The prepared cells consisting of the structure of a BaZr0.1Ce0.7Y0.2O3–δ (BZCY7)‐NiO anode substrate, a BZCY7 anode functional layer, a BZCY7 electrolyte membrane, and a cathode layer, are measured from 600 to 700 °C with humidified hydrogen (∼3% H2O) as the fuel and static air as the oxidant. The electricity results show that the cell with BCP40 cathode has a higher power density, which could obtain an open‐circuit potential of 0.99 V and a maximum power density of 378 mW cm–2 at 700 °C. The polarization resistance measured at the open‐circuit condition of BCP40 is only 0.16 Ω cm2 at 700 °C, which was less than BCP20. 相似文献
8.
In this study, planar anode‐supported solid oxide fuel cells (5 × 5 cm2) were fabricated with cathode segmentations and tested in a channel type setup. The in‐plane performance variation became significant with an increasing current density (fuel utilization), and impedance analysis on each segment indicated that the poor performance in the outlet region was due to gas conversion overpotential combined with gas concentration overpotential. Pt reference electrodes were embedded in the electrolyte layers of the segments so that the anode and cathode overpotential could be separated for each segment. It was found that the cathode overpotential was dominant for both segments, which suggested that the cathode overpotential determined the overall cell performance. On the other hand, the anode overpotential was responsible for the in‐plane performance variation. Post‐analysis revealed that the Ni anode was partially oxidized and its layer was delaminated in the outlet region. Thus, this study suggests that the anode overpotential related to gas conversion is a critical factor in determining Ni anode stability as well as overall cell performance in planar anode supported cells with a gas channel setup. 相似文献
9.
For investigating the direct applicability of highly active cobalt containing cathodes on YSZ electrolytes at a lower processing and operating temperature range (T ≤ 650 °C), we fabricated a thin film lanthanum strontium cobalt oxide (LSC) cathode on an yttria stabilised zirconia (YSZ)‐based solid oxide fuel cell (SOFC) via pulsed laser deposition (PLD). Its electrochemical performance (5.9 mW cm–2 at 0.7 V, 650 °C) was significantly inferior to that (595 mW cm–2 at 0.7 V, 650 °C) of an SOFC with a thin (t ∼ 200 nm) gadolinium doped ceria (GDC) buffer layer in between the LSC thin film cathode and the YSZ electrolyte. It implies that even though the cathode processing and cell operating temperatures were strictly controlled not to exceed 650 °C, the direct application of LSC on YSZ should be avoided. The origin of the cell performance deterioration is thoroughly studied by glancing angle X‐ray diffraction (GAXRD) and transmission electron microscopy (TEM), and the decomposition of the cathode and diffusion of La and Sr into YSZ were observed when LSC directly contacted YSZ. 相似文献
10.
《Fuel Cells》2017,17(3):344-352
In this report, we present a study of using nitrogen‐doped graphene as the air electrode of low temperature solid oxide fuel cells (LT‐SOFCs) operating at 350 °C or lower. Three graphene derivatives were prepared through hydrothermal reactions and their electrochemical performance and material properties were characterized in the temperature range of 225–350 °C in atmospheric air. Nitrogen‐doped graphene was found to exhibit a decent air electrode performance comparable to a porous Pt electrode aged for 8 h at 350 °C, but only for a limited time. After ∼10 h of operation at 350 °C, the electrode performance degraded significantly due to carbon oxidation. However, alternative routes of synthesizing/doping graphene derivatives are expected to improve the viability of using these materials as a practical high temperature air electrode. 相似文献
11.
Thermal cycling and creep in metallic interconnects during operation of solid oxide cell (SOC) stacks could cause contact losses in the interface between the interconnect and cells. The magnitude of stress and its distribution within the SOC stack depends on the overall design of the stack and the operating conditions. In this study, stresses in different types of generic SOC stack designs caused by external loading and temperature variations through long‐term operation are investigated. The investigation includes stack designs with and without contact components combined with machined (cross‐shaped) or pressed (corrugated) interconnects. Two different generic temperature profiles in the stacks are considered. Special focus is given to stresses that can cause possible delamination of the interconnect from the cell that subsequently leads to loss of electrical contact. It is found that too rigid designs cause high stresses and creep in the interconnects, and so‐called stress reversal will cause delamination between interconnect and cell during shut‐down. Furthermore, the study also presents the effect of SOC stack design and/or thermal gradient on the magnitude of in‐plane stresses in the cells. Here it is found that it advantageous to cool the stack primarily with convection, as this causes a linear thermal profile and much lower stresses than if cooling is relying on conduction in the solids, as this causes a thermal gradient in several directions. 相似文献
12.
Aqueous‐based tape casting is a low‐cost and environment friendly technology. In this paper, large‐area fuel electrode‐supported solid oxide cells (SOCs) were fabricated by this technology in conjunction with co‐sintering process. A 10 cm × 10 cm single cell with NiO/Zr0.92Y0.08O2–δ fuel electrode, Zr0.92Y0.08O2–δ electrolyte and La0.6Sr0.4Co0.2Fe0.8O3+δ/Ce0.9Gd0.1O2+δ air electrode has been successfully developed with improved electrode microstructure and hence the cell performance with the maximum power density of 534 mW cm–2 at 850 °C with humidified H2 as the fuel and air as the oxidant has been achieved. The optimal slurry formulations used in the fabrication of SOC were summarized for future reference purpose. 相似文献
13.
The effect of endothermic internal steam reformation of methane and exothermic fuel cell reaction on the temperature of a planar‐type anode‐supported solid oxide fuel cell was experimentally investigated as a function of current density and fuel utilization. We fabricated a large‐area (22 × 33 cm2) cell and compared temperature profiles along the cell using 30 thermocouples inserted through the cathode end plate at 750 °C under various conditions (Uf ∼50% at 0.4 A cm−2; Uf ∼70% at 0.4 A cm−2; Uf ∼50% at 0.2 A cm−2) with hydrogen fuel and methane‐steam internal reforming. The endothermic effect due to internal reforming mainly occurs at the gas inlet region, so this process is not very effective to cool down the hot spot created by the exothermic fuel cell reaction. This eventually results in a larger temperature difference on the cell. The most moderate condition with regards to thermal gradient on the cell corresponds to high fuel utilization (Uf ∼70%) and low current density (∼0.2 A cm−2). The electrochemical performance was also measured, and it was found that the current–voltage characteristics are comparable for the cell operated under hydrogen fuel and internal steam reforming of methane because of lower polarization resistance with high partial pressure of water vapor. 相似文献
14.
《Fuel Cells》2018,18(4):476-489
The applicability of online total harmonic distortion analysis (THDA) for the operation and monitoring of solid oxide fuel cell (SOFC) power systems is investigated by experiments as well as analysis of the algorithm, with a focus on the relationship between stack fuel utilization rate and the corresponding THD index. An online THDA algorithm is implemented in a programmable logic controller (PLC) and operated with a 6 kW SOFC power system demonstration unit. Laboratory experiments on the solid oxide fuel cell technology are carried out to determine key parameters for the algorithm. The embedded implementation of the THDA algorithm, including several modifications to reduce its computational load, and its parameterization is analyzed and the program code is given in the Appendix. The experimental results verify that THDA can be a reliable means for quantitatively monitoring the fuel utilization rate experienced by the stack and that the algorithm is simple to implement on an embedded controller. 相似文献
15.
H.‐T. Lim S. C. Hwang M. G. Jung H. W. Park M. Y. Park S.‐S. Lee Y.‐G. Jung 《Fuel Cells》2013,13(5):712-719
The degradation mechanism of anode‐supported planar solid oxide fuel cells is investigated in the present work. We fabricate a large‐area (10 cm × 10 cm) cell and carry out a long‐term test with the assembly components. A constant current of ∼0.4 A cm–2 is applied to the cell for ∼3,100 h, and the furnace temperature is controlled in the sequence 750–800–750 °C to investigate the effect of operating temperature and thermal cycling on the degradation rate. Impedance spectra and current–voltage characteristics are measured during the operation in order to trace any increase in Ohmic and non‐Ohmic resistance as a function of time. The degradation rate is rapid during the operation at the higher temperature of ∼800 °C compared to that during the operation at ∼750 °C. Even after cooling down to ∼750 °C, that rate is still accelerated. The main contribution to the cell degradation is from an increase in the Ohmic resistance. Postmaterial analyses indicate that the cathode is delaminated at the electrolyte/cathode interface, which is attributed to the difference in thermal expansion coefficient (TEC). Thus, the present results emphasize the importance of matching the TEC between cell layers, especially under severe operating conditions such as long duration and complex thermal cycling. 相似文献
16.
A non‐sealed solid oxide fuel cell stack with cells embedded in plane configuration was fabricated and operated successfully in a box‐like stainless‐steel chamber. For a two‐cell stack, it demonstrated an open circuit voltage (OCV) of 2.13 V and a maximum power output of 569 mW at the flow rate of 67 sccm CH4 and 33 sccm O2. A fuel utilization of 4.16% was obtained. The cell performance was dominated by two different mechanisms, the polarization of the cathode at low current and the concentration polarization of the anode at high current. Finally, a scaled‐up stack with six cells in series generated an OCV of 6.4 V and a maximum power output of 8.18 W. 相似文献
17.
An engineering analysis based on calibrated numerical predictions was performed to estimate the minimum allowable impurity concentrations in coal syngas intended to be used in Solid Oxide Fuel Cells (SOFCs) operating for over 10,000 h. Arsine and phosphine, impurities that are known to have the most deleterious effects on the cell performance due to their affinity to have strong relations with the anode catalyst by formation of secondary phases, were investigated. Time to failure was taken as the operation time when 60% performance loss is incurred, estimated by the previously developed one‐dimensional degradation model. Limiting concentrations were determined for arsine and phosphine fuel contaminants for electrolyte and anode supported SOFCs. Predicted lifetimes for single cells can provide a basis for estimation of SOFC stack lifetimes operating on coal syngas. Extrapolation of results from the numerical simulations based on accelerated laboratory tests at relatively higher concentrations can provide guidance into predicting the cell failure at low impurity concentrations. 相似文献
18.
High‐temperature ferritic alloys are potential candidates as interconnect (IC) materials and spacers due to their low cost and coefficient of thermal expansion (CTE) compatibility with other components for most of the solid oxide fuel cells (SOFCs). However, creep deformation becomes relevant for a material when the operating temperature exceeds or even is less than half of its melting temperature (in degrees of Kelvin). The operating temperatures for most of the SOFCs under development are around 1,073 K. With around 1,800 K of the melting temperature for most stainless steel (SS), possible creep deformation of ferritic IC under the typical cell operating temperature should not be neglected. In this paper, the effects of IC creep behaviour on stack geometry change and the stress redistribution of different cell components are predicted and summarised. The goal of the study is to investigate the performance of the fuel cell stack by obtaining the changes in fuel‐ and air‐channel geometry due to creep of the ferritic SS IC, therefore indicating possible changes in SOFC performance under long‐term operations. The ferritic IC creep model was incorporated into software SOFC‐MP and Mentat‐FC, and finite element analyses (FEAs) were performed to quantify the deformed configuration of the SOFC stack under the long‐term steady‐state operating temperature. It was found that the creep behaviour of the ferritic SS IC contributes to narrowing of both the fuel‐ and the air‐flow channels. In addition, stress re‐distribution of the cell components suggests the need for a compliant sealing material that also relaxes at operating temperature. 相似文献
19.
Reversible high temperature solid oxide cells (rSOC) can be operated both in the fuel cell (SOFC) and the electrolysis mode (SOEC). This specificity is a promising way to either store intermittent renewable energy surpluses by producing H2, or generate electricity from H2 or any other fuel locally available (CH4, biogas) when demand overtakes the local production. Therefore, rSOC technology could reinforce autonomy and flexibility in buildings, eco‐districts, up to industrial sites and local energy grids powered by intermittent renewable energies. Such a storage solution complements batteries, displays flexible energy storage durations, from a few hours up to seasonal cycles, and allows decorrelating power and storage capacity. Nonetheless, experiments are needed to assess whether rSOC systems can accommodate the surrounding environment and switch rapidly between various power levels and operating modes. An rSOC system has been built and its ability to operate in both electrolysis and fuel cell modes has been demonstrated. The present work is focused on transitioning between 3 operating modes (SOEC, SOFC operated in H2, SOFC operated in CH4), each displaying 3 power levels. The results show that all transition cycles could be done in 3 to 10 min without negatively affecting short term stack performances. 相似文献
20.
A series of iron‐based perovskite oxides BaFe1−xCuxO3−δ (x = 0.10, 0.15, 0.20 and 0.25, abbreviated as BFC‐10, BFC‐15, BFC‐20 and BFC‐25, respectively) as cathode materials have been prepared via a combined EDTA‐citrate complexing sol‐gel method. The effects of Cu contents on the crystal structure, chemical stability, electrical conductivity, thermal expansion coefficient (TEC) and electrochemical properties of BFC‐x materials have been studied. All the BFC‐x samples exhibit the cubic phase with a space group Pm3m (221). The electrical conductivity decreases with increasing Cu content. The maximum electrical conductivity is 60.9 ± 0.9 S cm−1 for BFC‐20 at 600 °C. Substitution of Fe by Cu increases the thermal expansion coefficient. The average TEC increases from 20.6 × 10−6 K−1 for BFC‐10 to 23.7 × 10−6 K−1 for BFC‐25 at the temperature range of 30–850 °C. Among the samples, BFC‐20 shows the best electrochemical performance. The area specific resistance (ASR) of BFC‐20 on SDC electrolyte is 0.014 Ω cm2 at 800 °C. The single fuel cell with the configguration of BFC‐20/SDC/NiO‐SDC delivers the highest power density of 0.57 W cm−2 at 800 °C. The favorable electrochemical activities can be attributed to the cubic lattice structure and the high oxygen vacancy concentration caused by Cu doping. 相似文献