Stability Of Solid Oxide Fuel Cells Research Articles

Enhanced performance of solid oxide fuel cells using highly conductive Ca2+ and F− co-doped Gd0.2Ce0.8O1.9 buffer layer

Gadolinium-doped ceria (GDC) is the most widely used buffer layer to prevent the reaction between YSZ electrolyte and La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathode for commercial solid oxide fuel cell (SOFC). However, conductivity and sintering activity are vital to cell performance. In this paper, Ca2+ and F− co-doped GDC (Ca0.03Gd0.17Ce0.8F0.06O1.84-δ, CGDCF) is used as a buffer layer to improve the performance and stability of SOFC. The co-doped F− and Ca2+ significantly improve the sintering properties and oxygen ion transport of traditional GDC material. Meanwhile, the optimized sintering temperature is 1300 °C, with the lowest ohmic resistance. The peak power density of a cell with a CGDCF buffer layer reaches 1.809 W cm−2 at 850 °C, which is 37 % higher than that of GDC. In addition, the cell with the CGDCF buffer layer exhibits excellent stability during the 150 h test owing to the lower migration of La and Sr elements. Thus, the Ca2+ and F− co-doped GDC oxide emerges as a promising material for buffer layer applications.

Direct ammonia SOFC – A potential technology for green shipping

International shipping carries about 90% of the global trade, thereby emitting significant amounts of greenhouse gasses by using fossil based fuels. Zero-emission technologies using green fuels are crucial to reduce the environmental impact of this important transport sector. Among the considered concepts is green ammonia in a solid oxide fuel cell (SOFC).The present study investigated SOFCs fueled with ammonia regarding cracking, electrochemical performance and durability. Ammonia cracking was for the first time directly measured over a planar, anode supported SOFC at open circuit voltage and during operation, as well as in presence of several balance of plant components. At temperatures around 700 °C, ammonia is significantly cracked when passing over hot metallic low surface area components (like Ni current collectors) even in the absence of the SOFC. The Ni/YSZ SOFC anode is active for the cracking as well. The area specific resistance of the SOFC is larger when using ammonia as compared to a H2/N2 mixture, due to two origins, (i) a decrease of the cell temperature due to the endothermal cracking, which leads to larger ohmic resistance and (ii) presence of unconverted ammonia, which increases the polarisation resistance in the low frequency region. Durability tests reveal increased cell voltage degradation when using ammonia fuel at 700 °C, mainly due to increase of the ohmic contributions. Micro structural analysis suggests nitridation as cause of this degradation. A stable SOFC operation is possible at 750 °C.

(Digital Presentation) Biogenic Electrodes for Low-Temperature Solid Oxide Fuel Cells

Biogenic Electrodes for Low-Temperature Solid Oxide Fuel Cells Jyoti Bhattacharjee, Subhasis Roy* Department of Chemical Engineering, University of Calcutta, 92 A. P. C. Road, Kolkata-700009, India * Email: subhasis1093@gmail.com/srchemengg@caluniv.ac.in : Solid oxide fuel cells (SOFCs) are potential energy-generation devices. They operate at hightemperatures, typically between 800°C-1000°C, limiting their utility. The primary challengein developing these fuel cells is synthesizing strong biogenic electrodes that function at lowtemperatures, maintaining high performance. This experimental study examines how eco-friendly,facile, and novel techniques for synthesis can be used to make robust, effective, and affordableelectrodes for low-temperature recyclable SOFCs (LT-SOFC). A green approachwas implemented by using biomass waste and biochar, specifically coconut shells and ricehusks, as raw materials. The synthesis comprised the hydrothermal carbonization of biomassprecursors, such as lignocellulosic nanostructures, and carbon nanotubes under controlledconditions, followed by activation with potassium hydroxide(KOH). The resulting electrodeshad a large surface area, catalytic oxygen reduction, excellent conductivity, and sufficientelectrochemical performance. The efficacy of the biomass-derived electrodes was enhancedby employing transition metal oxides as electrocatalysts, such as nickel oxide(NiO) andcobalt oxide(Co3O4). The morphology and elemental composition of the electrode materialwere studied using the scanning electron microscope(SEM) and energy-dispersive X-rayspectroscopy(EDS). Electrochemical impedance spectroscopy(EIS)was used to examine theelectrochemical properties of cell electrolytes. Findings demonstrated that the hydrothermalstrategy led to the formation of homogeneous and porous electrode structures with highgalvanic activity. The biodegradable LT-SOFC stack achieved an optimal power density of346mW/cm2 at around 550°C, indicating a substantial increase over previous experiments.Our results have significant economic consequences for the expansion of sustainable andrenewable energy innovations in industry and nanotechnology, providing auxiliary power inautomobiles and hydrogen generation. Greenhouse gas emissions and carbon footprint can bediminished by using biomass waste streams as feedstocks, reducing the need for fossil fuels.The outcomes of this research provide important insights into the development, challenges,and future possibilities of biomass-derived electrodes, and minimal temperature electrolytesfor stable SOFCs. Keywords: Biomass-derived; carbon footprint; electrochemical efficiency; green energy; low-temperature solid oxide fuel cells; nanotubes.

Effect of Calcination Temperature on the Structural and Electrochemical Behaviour of Li-Based Cathode for Intermediate-Temperature SOFC Application

A new strategy to reduce the operating temperature of the solid oxide fuel cell (SOFC) is needed to foster the progress of developing high-performance and stable SOFC as a solution to the thermal stress and degradation of the cell components induced by high-temperature SOFC. The use of lithium (Li) as a cathode can increase the cell’s efficiency, as it allows for faster ion transport and a higher reaction rate. This study presents an attractive approach to using a Li-based cathode by combining Li with cobalt (Co) to form LiCo0.6Sr0.4O2 (LCSO). In this work, a precursor consisting of Li, Co, and strontium (Sr) was prepared via the glycine-nitrate combustion method. The precursor was calcined at two different calcination temperatures (800 and 900 °C) prior to ink formulation and symmetrical cell fabrication in order to study the effect of calcination temperature on the structural and electrochemical behaviour of a Li-based cathode. The precursor LCSO powder was characterised using X-ray crystallography (XRD) to determine the crystal structure and composition of the developed LCSO. The electrochemical performance of the fabricated symmetrical cell was tested using electrochemical impedance spectroscopy (EIS) to obtain the cell’s resistance information, which is related to the cell’s ionic and electronic conductivity. SDC electrolyte with LCSO calcined at 800 °C has a higher crystallinity percentage and a more porous structure compared to LCSO calcined at 900 °C. The porous structure enhanced the electrochemical performance of the cell, where the symmetrical cell has the highest conductivity (0.038 Scm−1) with the lowest activation energy (0.43 eV). The symmetrical cell was also able to achieve 2.89 Ω cm2 of area-specific resistance (ASR) at 800 °C of operating temperature. In conclusion, the SDC electrolyte with LCSO calcined at 800 °C is the promising cathode material for SOFC applications. The result of this study can benefit the SOFC field of research, especially in the development of intermediate temperature-SOFC.

A Brief Review on Recent Advancement of Anode Materials for Biogas-Fed Solid Oxide Fuel Cells (SOFCs)

Solid Oxide Fuel Cell (SOFC) is a fuel cell technology run at high temperatures which enable internal reforming of fuel and production of high-quality by-product heat for cogeneration. The most distinguished advantage of SOFC is its excellent fuel flexibility. Biogas is one of the alternative fuels to preferable pure hydrogen. One of the important issues in operating SOFC with biogas is the formation of carbon on anode surface. Therefore, the development of coking-resistant anode materials is essential to create a high performance and stable biogas-fed SOFC. This review provides a brief survey on the recent progress of anode materials, mainly Ni-based cermet, and the modifications to prevent carbon deposition. The current situation of biogas production and utilization in Indonesia is also briefly reviewed.

Utilization of an Isovalent Doping Strategy in Cobalt-Free Ferrites for Highly Active and Stable Solid Oxide Fuel Cell Cathodes

Utilization of an Isovalent Doping Strategy in Cobalt-Free Ferrites for Highly Active and Stable Solid Oxide Fuel Cell Cathodes

In Situ Evaluation of the Influence of Interstitial Oxygen on the Elastic Modulus of La2NiO4

Lattice defects significantly affect the mechanical properties of crystalline metal oxides. The materials for the components of solid oxide fuel cells (SOFCs) are no exception, and hence understanding of the interplay between lattice defects and the mechanical properties of components is important to ensure the mechanical stability of SOFCs. Herein, we performed an in situ evaluation of the temperature and P(O2) dependence of the elastic moduli of La2NiO4 (LN214), a candidate for the cathode material of SOFCs, using the resonance method to understand the influence of interstitial oxygen on its elastic properties. Above 873 K, both the Young’s and shear moduli of LN214 slightly decreased with increasing P(O2), suggesting that these elastic moduli are correlated with interstitial oxygen concentration and decreased with increasing interstitial oxygen. We analyzed the influence of interstitial oxygen on the Young’s modulus of LN214, based on numerically obtained lattice energy. The P(O2) dependence of the Young’s modulus of LN214 was found to be essentially explained by variation in the c-lattice constant, which was triggered by variation in interstitial oxygen concentration. These findings may contribute to a better understanding of the relationship between lattice defects and mechanical properties, and to the improvement of the mechanical stability of SOFCs.

Highly Active and Stable a-Site Deficient La0.4Sr0.4Ti0.94Ni0.06O3-δ SOFC Anode Material with in-Situ Exsolved of Ni Nanoparticles

La-doped strontium titanates with a perovskite structure are promising candidates of the anode materials for solid oxide fuel cells (SOFCs) owing to their good chemical compatibility with other components and superior redox-stability. Among these La-doped SrTiO3 (LST), A-site deficient LST materials have attracted much interest due to their improved electrochemical characteristics. Recently, exsolution in A-site deficient LST has been intensively studied, because catalytic active and durable metal nanoparticles can be exsolved on the LST surface. In this study, we developed the A-site deficient Ni-doped La0.4Sr0.4TiO3 (LSTN)-Ce0.9Gd0.1O1.95 (GDC) composite anodes, and investigate their electrochemical performance and redox stability on La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) electrolyte-based SOFCs. The maximum power density(MPD) of LSTN44-GDC anode based cell was 0.698 mW cm-2 at 900℃ in wet H2 fuel (3% H2O). Also, during redox cyclic tests combined with long-term stability test, The LSTN44-GDC cell maintained its performance without any degradation. All these results demonstrate that the A-site deficient LSTN-GDC is a promising material for an efficient and stable SOFC anode.

Encapsulation of Metal Catalysts for Stable Solid Oxide Fuel Cell Cathodes

Metal catalysts have been employed as cathodes for solid oxide fuel cells to facilitate the surface exchange rate in the intermediate temperature range (600–800 °C). However, incorporated metal catalysts easily agglomerate, resulting in the loss of the reaction sites; thus, the electrochemical performance rapidly deteriorates over time. To hinder the agglomeration of metal catalysts while maintaining the catalytic activity, we encapsulated metal catalysts with nano-particulated perovskite materials using an infiltration technique. The encapsulation of Ag nanoparticles with nano-particulated Sm0.5Sr0.5CoO3-δ (SSC) successfully prevented the agglomeration of Ag nanoparticles, maintaining the initial polarization resistance for 200 h at 650 °C, while the polarization resistance of the SSC electrodes with the Ag nanoparticles increased by ~ 190% after 200 h at 650 °C because of the thermal agglomeration of Ag nanoparticles.

The role of the ceria dopant on Ni / doped-ceria anodic layer cermets for direct ethanol solid oxide fuel cell

The effect of ceria dopant aiming at stability in Ni/doped-ceria anodic layers for direct ethanol solid oxide fuel cells (SOFC) was studied. Solid solutions of ceria doped with Y, Gd, Zr, or Nb (10 mol%) impregnated with NiO were tested in a fixed bed reactor for ethanol conversion reactions and for direct (dry) ethanol SOFC. The ceria dopant showed a marked effect on both the catalytic and the electrical transport properties of the ceramic support. Catalytic activity data revealed that the studied materials deactivate in ethanol decomposition reaction but are stable for ethanol steam reforming. Thus, feeding dry ethanol to the SOFC with a Ni/doped-ceria anodic catalytic layer evidenced that water produced from the electrochemical hydrogen oxidation provides steam for the internal reforming resulting in great stability of the fuel cells tested during ~100 h. The combined catalysis and SOFC results demonstrate Ni/doped-ceria is as candidate anode layer for stable SOFC running on bioethanol.

High performance of direct methane-fuelled solid oxide fuel cell with samarium modified nickel-based anode

Natural gas is one of the most attractive fuels for solid oxide fuel cell (SOFC), while the anode activity for methane fuel has a great influence on the performance and stability of SOFC. Samarium is a good catalyst promoter for methane reforming. In this work, samarium is used to modify nickel catalyst, which results in small nickel oxide particles. The SmNi-YSZ (yttria-stabilized zirconia) anode has smaller particles and better interfacial contact between nickel and YSZ compared with conventional Ni-YSZ anode. The fine structure of SmNi-YSZ anode results in high activity for electrochemical oxidation of hydrogen and low polarization resistance of the cell. The performance of SmNi-YSZ anode cell with humidified methane as fuel is greatly improved, which is similar to that with hydrogen as fuel. The maximum power densities of SmNi-YSZ anode cell are 1.56 W cm−2 for humidified hydrogen fuel and 1.54 W cm−2 for humidified methane fuel at 800 °C. The maximum power density is increased by 221% when samarium is used to modify Ni-YSZ anode for humidified methane fuel at 650 °C. High cell performance results in good stability of SmNi-YSZ anode cell and the cell runs stably for more than 600 min for humidified methane fuel.

Engineering of Charged Defects at Perovskite Oxide Surfaces for Exceptionally Stable Solid Oxide Fuel Cell Electrodes.

Cation segregation, particularly Sr segregation, toward a perovskite surface has a significant effect on the performance degradation of a solid oxide cell (solid oxide electrolysis/fuel cell). Among the number of key reasons generating the instability of perovskite oxide, surface-accumulated positively charged defects (oxygen vacancy, Vo··) have been considered as the most crucial drivers in strongly attracting negatively charged defects (SrA-site') toward the surface. Herein, we demonstrate the effects of a heterointerface on the redistribution of both positively and negatively charged defects for a reduction of Vo·· at a perovskite surface. We took Sm0.5Sr0.5CoO3-δ (SSC) as a model perovskite film and coated Gd0.1Ce0.9O2-δ (GDC) additionally onto the SSC film to create a heterointerface (GDC/SSC), resulting in an ∼11-fold reduction in a degradation rate of ∼8% at 650 °C and ∼10-fold higher surface exchange (kq) than a bare SSC film after 150 h at 650 °C. Using X-ray photoelectron spectroscopy and electron energy loss spectroscopy, we revealed a decrease in positively charged defects of Vo·· and transferred electrons in an SSC film at the GDC/SSC heterointerface, resulting in a suppression of negatively charged Sr (SrSm') segregation. Finally, the energetic behavior, including the charge transfer phenomenon, O p-band center, and oxygen vacancy formation energy calculated using the density functional theory, verified the effects of the heterointerface on the redistribution of the charged defects, resulting in a remarkable impact on the stability of perovskite oxide at elevated temperatures.

Thermodynamic analysis and fuel processing strategies for propane-fueled solid oxide fuel cell

Propane is a particularly attractive fuel for solid oxide fuel cell (SOFC) because it is cheap, widely available and easily stored with high energy density, while carbon deposition may be a serious problem in direct propane-fueled SOFC, thus efficient propane processing strategy is favored by SOFC. The fuel compositions, efficiency and stability of SOFC may be affected by propane processing strategies apparently. In this paper, the fuel compositions and cell efficiency are investigated for different propane pre-treating techniques. For steam reforming, CO2 reforming and anode off-gas reforming of propane, the decreasing rates of real fuel utilization and cell efficiency are apparently different with the change of equivalent fuel utilization. At high equivalent fuel utilization, the real fuel utilization and cell efficiency decrease slowly with the increase of oxygen to carbon (O/C) ratio. While at low equivalent fuel utilization, the real fuel utilization and cell efficiency decrease rapidly with the increase of O/C ratio. For catalytic partial oxidation of propane, the real fuel utilization and cell efficiency decrease rapidly and the decreasing rate is same at different equivalent fuel utilization with the increase of O/C ratio. Suitable proportions of steam, carbon dioxide and/or oxygen in the feed and efficient propane processing strategy can depress the carbon deposition and improve the cell efficiency.

An easily sintered and chemically stable La2-xMgxCe2O7-δ proton conductor for high-performance solid oxide fuel cells

Abstract Mg-doped La2Ce2O7-δ (LCO) is investigated to develop an easily sintered and chemically stable proton conductor for fabricating high-performance solid oxide fuel cells (SOFCs). All La2-xMgxCe2O7-δ ceramics possess a pure fluorite-type structure. The sintering activity of Mg-doped LCO increases obviously, and fully dense La1.85Mg0.15Ce2O7-δ (LMCO) electrolyte membrane is successfully prepared by co-firing at the temperature as low as 1300 °C for 5 h. Besides, LMCO exhibits the highest electrical conductivity of 7.41 × 10−3 S cm−1 in dry air and 1.55 × 10−2 S cm−1 in wet H2 (∼3% H2O) at 700 °C among the investigated oxides, and retains excellent chemical stability against CO2 and H2O. The LMCO-based fuel cell also displays very encouraging power performance, reaching as high as 897 mWcm−2 at 700 °C. The results demonstrate LMCO is a promising alternative as proton conductor for achieving both chemically stable and high-performance SOFCs with reduced sintering temperature.

A-site deficient La0.4Sr0.4TiO3-Ce0.9Gd0.1O1.95 composites as efficient and redox stable anodes for solid oxide fuel cells

La-doped strontium titanates have attracted much interest as promising reliable ceramic anodes for solid oxide fuel cells (SOFCs) owing to their superior redox-stability. Moreover, recent studies demonstrated that A-site deficiency of the La-doped SrTiO3 perovskite could effectively promote conductivity and catalytic activity, simultaneously. In this study, we developed the LST44-Ce0.9Gd0.1O1.95 (GDC) composite anodes, and investigated their electrochemical performance and redox stability on La0.8Sr0.2Ga0.8Mg0.2O3−δ (LSGM) electrolyte-based SOFCs. During galvanostatic long-term stability tests combined with in situ redox cycles, power out-put performance of the LST44-GDC employed SOFC was initially increased by ∼53% to 0.26 W cm−2 and maintained the high performance over 350 h at 800 °C. Analysis of the accumulated electrochemical impedance spectra during the long-term stability test showed that the electrochemical activity of the LST44-GDC anode was promoted at the initial redox cycling. Consequently, this study demonstrates that A-site deficient LST44-GDC is a promising material as an efficient and redox stable SOFC anode.

Material Discovery and Design Principles for Stable, High Activity Perovskite Cathodes for Solid Oxide Fuel Cells

AbstractCritical to the development of improved solid oxide fuel cell (SOFC) technology are novel compounds with high oxygen reduction reaction (ORR) catalytic activity and robust stability under cathode operating conditions. Approximately 2145 distinct perovskite compositions are screened for potential use as high activity, stable SOFC cathodes, and it is verified that the screening methodology qualitatively reproduces the experimental activity, stability, and conduction properties of well‐studied cathode materials. The calculated oxygen p‐band center is used as a first principle‐based descriptor of the surface exchange coefficient (k*), which in turn correlates with cathode ORR activity. Convex hull analysis is used under operating conditions in the presence of oxygen, hydrogen, and water vapor to determine thermodynamic stability. This search has yielded 52 potential cathode materials with good predicted stability in typical SOFC operating conditions and predicted k* on par with leading ORR perovskite catalysts. The established trends in predicted k* and stability are used to suggest methods of improving the performance of known promising compounds. The material design strategies and new materials discovered in the computational search help enable the development of high activity, stable compounds for use in future solid oxide fuel cells and related applications.

Chemical Analysis of Activation Process of LSM Thin Film Electrode

Strontium-doped lanthanum manganite (LSM) is one of the most widely used cathode material for yttria-stabilized zirconia (YSZ)-based solid oxide fuel cells (SOFCs), due to its superior chemical stability and small coefficient of thermal expansion (TEC) mismatch with YSZ. The activation process of the cell, which can be attributed to the cathode and cathode electrode interface, has a significant effect on the long-term electrochemical performance and stability of SOFCs. Therefore, it is essential to understand the origin of this underlying activation process. In this study, thin film LSM on YSZ half cells were fabricated with an LSCF counterelectrode and the effects of cathodic current density and overpotential on the polarization behavior of the LSM thin film electrode were investigated. The surface morphology as well as surface chemistry and bonding environment of LSM before and after polarization was investigated using scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The formation of SrO was found on the LSM surface after polarization. The cross-section microstructure of LSM, as well as interfacial chemistry of LSM/YSZ, were investigated using transmission electron microscope (TEM) and TEM-based energy dispersive X-ray spectroscopy (EDS). The presence of Mn-rich phases were observed before and after polarization. The pre- and post-activation electrode performances were investigated at various temperatures and oxygen partial pressures, which helps reveal the nature of the activation mechanism in combination with the microstructural and chemical analysis.

Sulfur Poisoning of Ni/CGO Anodes: A Long-Term Degradation Study

Although continuous progress is achieved with respect to lifetime and performance improvements, solid oxide fuel cells (SOFC) continue to struggle with commercialization. One important factor to possibly reduce overall costs of SOFC systems would be the omission of desulfurization units during the fuel processing. However, sulfur-containing impurities in the most common fuels such as natural gas and biogas lead to significant performance drops upon exposure to Ni-based anodes. In this regard, it has been shown that Ni/gadolinium-doped ceria (CGO) anodes display lower performance drops upon short-time sulfur exposure than Ni/YSZ. However, their long-term resistivity towards sulfur exposure has not been investigated so far, although this is likely to be the most vital factor determining SOFC lifetime. This work presents the first in-depth analysis of long-term degradation due to sulfur poisoning of Ni/CGO10-based SOFC. A parameter study of the sulfur-induced long-term degradation of commercial, high-performance single cells was conducted with an accumulated cell testing time of more than one year. The long-term degradation behavior is investigated at 900 °C for different H2S concentrations and varying H2/H2O/N2 fuel gas atmospheres. The sulfur poisoning periods of the different cells varied from 100 up to 1500 h. The progress of the degradation during the experiments was monitored by means of electrochemical impedance spectroscopy. It is shown that Ni/CGO anodes can be exposed to 10 ppm H2S and operated without significant irreversible degradation at a current density of 0.5 A·cm–2 for 1500 h for certain fuel gas mixtures, demonstrating their promising long-term stability. However, for reduced hydrogen partial pressures in the fuel gas, the same H2S concentration leads to a considerable voltage decrease that is reflected by an increase in anode charge transfer and ohmic resistance. Furthermore, the microstructural evolution of the Ni/CGO is examined ex-situ by means of SEM and correlated to the anode performance degradation. The existence of a stable operating regime for Ni/CGO anodes under sulfur exposure is clearly shown and the critical operating parameters are outlined. The presented results give important insights into the degradation processes occurring during long-term operation of Ni/CGO anodes as well as strategies for stable SOFC operation. Moreover, the results encourage to further optimize the performance and sulfur tolerance of Ni/CGO anodes.

Highly Effective Catalysts Supported on Metal Foams for Reforming Hydrocarbons for SOFCs

The development of highly efficient modular power generation units is of great importance. Solid oxide fuel cells (SOFC) are currently considered as the most efficient devices for the conversion of hydrocarbons, (natural gas, LPG, JP or diesel) into electric power. To provide stable SOFC operation, initial fuel, before feeding to the SOFC anode, should be converted to synthesis gas with high hydrogen content. Catalytic steam, combined steam-dry, partial oxidation or autothermal reforming are the most appropriate reactions for this purpose. The optimum temperature for these reactions is 550 − 900 °C, which falls within the SOFC working temperature range. The development of a catalyst system that can act as a combined catalytic reformer and heat exchanger (to remove or supply heat at the reaction zone) is very promising for efficient power generation. The combined catalytic reformer and heat exchange catalyst should have the following characteristics: high intrinsic activity with respect to its weight and volume (due to size limitations of the reformer); coking resistance; high intrinsic heat conductivity (in order to provide uniform temperature and reaction rate distribution across the reformer); low pressure drop. The present report summarizes the results obtained during a systematic study of several new nickel- and rhodium- based catalyst compositions supported on metal foams, their performance, and fundamental principles of the above mentioned reactions for conversion of various common hydrocarbon fuels. A procedure for deposition of active catalyst components onto metal foams has been developed. It was systematically verified on Ni, Ni-Fe, FeCrAlY-steel foams with porosity from 10 to 70 pores per inch (ppi), obtained from various manufacturers. The catalytic performance of the coated metal foam substrates was studied in a fixed-bed continuous flow reactor. Total feed flow rate (GHSV − gas hourly space velocity) ranged from 3,000 to 30,000 hr-1. The reaction temperature varied from 500 to 800 °C. The catalysts (as-synthesized and used) were characterized by BET, XRD, XPS, TEM, EDX, SEM, TPR and TPD techniques.

Probing Temperature Inside Planar SOFC Short Stack, Modules, and Stack Series

Probing temperature inside a solid oxide fuel cell (SOFC) stack lies at the heart of the development of high-performance and stable SOFC systems. In this article, we report our recent work on the direct measurements of the temperature in three types of SOFC systems: a 5-cell short stack, a 30-cell stack module, and a stack series consisting of two 30-cell stack modules. The dependence of temperature on the gas flow rate and current density was studied under a current sweep or steady-state operation. During the current sweep, the temperature inside the 5-cell stack decreased with increasing current, while it increased significantly at the bottom and top of the 30-cell stack. During a steady-state operation, the temperature of the 5-cell stack was stable while it was increased in the 30-cell stack. In the stack series, the maximum temperature gradient reached 190°C when the gas was not preheated. If the gas was preheated and the temperature gradient was reduced to 23°C in the stack series with the presence of a preheating gas and segmented temperature control, this resulted in a low degradation rate.