Temperature Solid Oxide Fuel Cells Research Articles

Three-Dimensional Numerical Study of the Anode Supported Intermediate Temperature Solid Oxide Fuel Cell Overheating

Three-Dimensional Numerical Study of the Anode Supported Intermediate Temperature Solid Oxide Fuel Cell Overheating

Optimization of sintering temperature for SOFCs by a co-firing method

A single-step co-firing process is employed to fabricate solid oxide fuel cells (SOFCs) with an Sm-doped CeO2 (SDC) electrolyte, aiming to simplify the SOFC fabrication procedure. Complete tri layer green cells are co-fired in a single step at different fabrication temperatures, and the co-firing temperature significantly influences the cell microstructure and thus influences its performance. Electrochemical investigations indicate that the cell resistance, including the ohmic and polarization resistance, varies with the co-firing temperatures used and leads to a different cell power output. Although the cell polarization resistance follows the rule that higher firing temperatures lead to higher polarization resistance values, the cell ohmic resistance does not follow the expectation that the cell fired at 1200 °C gives the largest ohmic resistance. The morphology analysis reveals the mechanism behind this phenomenon. The best cell performance is obtained by co-firing the cell at 1000 °C, reaching 401 mW cm−2 at 700 °C.

BaCo1‐xNbxO3−δ as a Promising Cathode for Intermediate Temperature Solid Oxide Fuel Cells

AbstractNb2O5 doped BaCoO3‐δ was synthesized using traditional solid‐state reaction method. The electrochemical performance, physical properties and rate‐determining step of BaCo1‐xNbxO3−δ as a cathode material for intermediate‐temperature solid oxide fuel cells (IT‐SOFCs) were investigated. The introduction of Nb in BaCo0.8Nb0.2O3‐δ(BCN20)brings a stable cubic phase and a relative lower TEC (∼16.94×10‐6 K−1) compared BCN20 with other Co‐based perovskites. The oxygen vacancy concentration (δ) for BCN20 symmetrical cell is 0.153. The area specific resistance (ASR) of BCN20 symmetrical cell is merely 0.0397 Ω⋅cm2 at 700 °C. Base on the above findings, BCN20 has a great electrochemical performance as a cathode material for IT‐SOFCs. Furthermore, we studies the reaction mechanism of BCN20 and concluded that desorption and diffusion of oxygen molecules is the oxygen reduction rate limiting step. Finally, full cell with BCN20 as cathode was tested and peak power density was measured to be 1042 mW⋅cm−2 at 800 °C.

Applicability of the SOFC technology for coupling with biomass-gasifier systems: Short- and long-term experimental study on SOFC performance and degradation behaviour

Coupling biomass gasification with high temperature Solid Oxide Fuel Cells (SOFCs) is a promising solution to increase the share of renewables and reduce emissions. The quality of the producer gas used can, however, significantly impact the SOFC durability and reliability. The great challenge is to ensure undisturbed operation of such system and to find a trade-off between optimal SOFC operating temperature and system thermal integration, which may limit the overall efficiency. Thus, this study focuses on experimental investigation of commercial SOFC single cells of industrial size fueled with different representative producer gas compositions of industrial relevance at two relevant operating temperatures. The extensive experimental and numerical analyses performed showed that feeding SOFC with a producer gas from a downdraft gasifier, with hot gas cleaning, at an operating temperature of 750 °C represents the most favorable setting, considering system integration and the highest fuel utilization. Additionally, a 120 h long-term test was carried out, showing that a long-term operation is possible under stated operating conditions. Local degradation took place, which can be detected at an early stage using appropriate online-monitoring tools.

The influence of activated carbon as an additive in anode materials for low temperature solid oxide fuel cells

The effects of activated carbon (AC) as an additive in multi-oxide nano composite LiNiCuZn–O for application as anode in solid oxide fuel cell (SOFC) is reported. The composite was synthesized using solid state reactions method with varying content of AC in range 0.1%–0.9% for use as anode in the cell. The cell was composed of the synthesized composite as anode, LiNiCuZn–O as cathode and Samaria doped ceria (SDC) as electrolyte. The prepared composites were characterized for morphology and crystal structure by scanning electron microscope (SEM) and x-ray diffraction (XRD) respectively. Furthermore, the crystallite sizes of LiNiCuZn–O and LiNiCuZn–O with AC as an additive have been found in the range from 50 nm to 70 nm. The prepared composite materials were observed porous and the porosity of the sample having 0.5% additive was found highest. The conductivity and power density of the SOFC were studied at temperature of 600 °C. The maximum value of conductivity was found as 4.79 S/cm for the composite containing 0.5% AC as measured by using 4-probe method. The maximum value of power density of the fuel cell with anode comprising of 0.5% AC along with the mentioned cathode and the electrolyte was 455 mW/cm2. Therefore, out of the compositions studied, the composite comprising of LiNiCuZn–O with 0.5% AC offered best performance for anode in the cell. This oxide composite is reported as a potential candidate for use as anode in low temperature SOFCs.

Improvement of Electrochemical Performance of Thin Film Mixed Ionic Electronic Cathode for Low Temperature Solid Oxide Fuel Cells By Additional Catalytic Current Collecting Layer

In the present study, catalytic current collecting layer (CCCL) was added to thin film La0.6Sr0.4Co0.8Fe0.2O1-δ (LSCF) cathode for low temperature solid oxide fuel cells (LT SOFCs) to improve both electrical current collection and catalytic activity. By adding CCCL, the maximum power density improved nearly 10-fold compared to the bare LSCF cathode. With thicker Pt or Pd CCCL, ohmic loss in current collection and oxygen reduction reaction (ORR) activity were both improved. Due to smooth oxygen ion conduction of solid oxide electrolytes, a typical range of operating temperature of SOFCs is 800 ~ 1000 ℃, which imposes a number of obstacles for SOFCs to be commercialized. Lots of studies have been carried out to make the operating temperature lower, down to 400 ~ 600 ℃. However, not only ion conduction in electrolytes but also ORR activity in cathode highly depends on temperature. As the operating temperature goes down, the faradaic impedance of SOFCs become severe because of sluggish ORR at a lower temperature. LSCF, one of the widely used cathode material in SOFCs, shows poor ORR activity and electronic conductivity at this temperature range. Therefore, Pt has been mainly used as electrode material for LT SOFCs based on its superior catalytic activity in lower temperature but it suffers from thermal instability, such as agglomeration. In this report, the noble catalysts, Pt and Pd, were investigated as the CCCL for mixed ionic electronic conductor LSCF cathode to enhance both electronic conductivity and catalytic activity at 550 ℃. LSCF cathode was deposited on the single crystal (100) YSZ pellet by using PLD. For the CCCL, Pt and Pd were adopted and deposited via direct current (DC) magnetron sputtering on the LSCF cathode. The thickness of the CCCL was varied from 100 nm to 300 nm. Ni was used as anode and deposited on the other side of the pellet via DC magnetron sputtering for about 300 nm. GDC interlayer with thickness of approximately 250 nm was applied between YSZ pellet and LSCF cathode to block formation of any insulation layer through reaction between YSZ and LSCF. Electrochemical performance was investigated through i-V plot and EIS and long-term stability was measured with Galvanostatic mode. The microstructure of LSCF and CCCL were investigated through FIB-SEM, FE-SEM. Crystal structure of the LSCF cathode CCCL was studied with XRD.

Large Enhancement of Oxygen Surface Exchange Kinetics in Ruddlesden–Popper Thin Films By Thickness Controlled Strain

The design of highly active catalysts for the oxygen reduction reaction (ORR) that leads to the majority of efficiency loss is a critical requisite in the needs of intermediate temperature solid oxide fuel cells (SOFCs). Introducing the lattice strain of an epitaxial film induced by lattice mismatch with a substrate enables a new way to enhance the ORR at elevated temperatures. However, very limited available electrolytes to induce strains in high temperature electrochemical applications, in which yttria-stabilized zirconia (YSZ) uniquely satisfies both the growth requirements (i.e. lattice mismatch) and the electro-chemical requirements (i.e. ionic conductor and electronic insulator) impose a constraint on applying the lattice strain. The limited choice of substrates imposes a constraint on the range of lattice strains, which suggests the need to develop a new strategy to modulate the epitaxial strain for designing catalytically active materials. In this work, we explore the dramatically enhanced ORR kinetics in the Ruddlesden–Popper oxide, LaSrCoO4 (LSC214), which have been highlighted as alternative cathode materials for intermediate temperature SOFCs grown on (001) YSZ substrates using film thickness to control the epitaxial strain. Pulsed laser deposition (PLD) is employed to deposit LSC214 thin films with four different film thicknesses. Electrochemical impedance spectroscopy (EIS) results demonstrate that the oxygen surface exchange coefficient (k q) values of ~ 15 nm LSC214 thin film with only ~1 % in-plane tensile strain can be dramatically enhanced by up to two orders of magnitude compared to fully relaxed thicker films (~70 and 140 nm). We find that this enhancement is strongly associated with a change of the surface chemistry revealed from Auger electron spectroscopy (AES), which can lead to a change of the electronic structure, the oxygen 2p band center relative to the Fermi energy level. In addition, we also show no discernible change in the k q values at low oxygen partial pressures regardless of the film thickness. This result suggests that the rate-limiting step for the oxygen surface exchange in LSC214 thin films changes depending on the oxygen partial pressure. Our work illustrates that controlling thickness is a new strategy to design highly active oxide materials for applications of complex oxides in the solid-state electrochemistry.

Characterization of Cerium Dioxide Thin Films Prepared By Plasma-Enhanced Atomic Layer Deposition for Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) are considered to be the next generation of energy conversion devices because of their environmental friendliness and high efficiency. Particularly due to its high operating temperature, it has high fuel flexibility and does not require water management. However, the high operating temperature that causes these advantages accelerates the degradation of fuel cell components, thereby reducing the durability and limiting the usable materials. Therefore, in recent years, a lot of research has been conducted to lower the operating temperature of the SOFCs. One method of lowering the operating temperature of SOFCs is to apply an electrolyte having good ionic conductivity at low temperatures(400-600℃). Potential examples are doped ceria materials. One of the well-known ceria-based electrolytes is Gd-doped ceria (GDC), which exhibits ion conductivity 1-2 times higher than yttria stabilized zirconia, YSZ, which is the most commonly used electrolyte in SOFC. GDC has good ionic conductivity, but when exposed to a reducing environment, Ce4+ is reduced to Ce3+ and begins to have electronic conductivity, which causes a decrease of open circuit voltage (OCV). Therefore, in order to apply GDC as an electrolyte, an additional blocking layer must be added so that it is not exposed to the hydrogen environment of the anode. This additional layer increases not only the thickness of the electrolyte but also the interfacial resistance between the layers, thereby increasing the ohmic resistance. Therefore, the fabrication of GDCs with thinner and better surface properties is critical to improving the performance of low temperature SOFCs. In this study, CeO2 thin film was fabricated using atomic layer deposition (ALD) as a preceding step for the fabrication of GDC thin films. Oxygen plasma was used to oxidize the precursor to widen the ALD window and to produce the highly crystalline CeO2. The growth rate of CeO2 was determined by controlling precursor and oxidizer exposure time, and the thickness of thin film per cycle was confirmed. The surface morphology was observed by scanning electron microscope (SEM), and dense and pinhole-free thin film surface was confirmed. In addition, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses were performed and the characteristic crystalline peaks and chemical compositions were compared with those of the thermal ALD CeO2 thin films.

Fabrication and Characterization of Thin Film SrCo0.8Nb0.1Ta0.1O3-Δ By Pulsed Laser Deposition

High working temperature(≥800 °C) of solid oxide fuel cell(SOFC) causes high cost of balance of plant, long start up time, and low durability. To overcome these barriers, lowering the working temperature of SOFC is one of the most attractive ways and such strategy has been researched through the fabrication of thin electrolyte and developing new perovskite cathode material. Recently, mixed ionic electronic conducting(MIEC) cathode material, SrCo0.8Nb0.1Ta0.1O3-δ (SCNT), has been developed by Li et al. and the SOFC with the cathode showed high performance(1.22W/cm2) at low working temperature (500 °C) with 14µm thick gadolinia doped ceria(GDC) electrolyte[1]. To apply SCNT to SOFC with thin electrolyte(≤1µm), the cathode must be fabricated on the electrolyte without high temperature sintering process(≥1000 °C) because of the weak mechanical strength of thin electrolyte. In this work, pulsed laser deposition(PLD) method was employed for the fabrication of thin film SCNT. PLD has been used widely for perovskite material deposition because of its high preservability of stoichiometric ratio of its original target material. However, the deposition temperature of PLD has a great influence on both physical and chemical structure of the film which means oxygen reaction activity(ORR) of the film also varies as temperature changes. Therefore, thin film SCNT was deposited by PLD at various temperature condition in this work to see the diversity of thin film characteristic for understanding the feasibility of application of SCNT to thin film SOFC (TF-SOFC). Powder and PLD target of SCNT were both prepared by the method Li et al. used, solid state reactive sintering(SSRS). The film was firstly deposited on Si wafer at various temperature (room temp, 500, 600, 700 °C) by PLD. Field emission scanning electron microscope (FE-SEM) and focused ion beam-SEM (FIB-SEM) were used to see the nano-structure of the film and deposition rate. 75mTorr of oxygen atmosphere was enough to make the structure of thin film deposited at room temperature very porous but dense film was observed at the temperature higher than 500 °C. The atomic ratio and crystallinity of each film were identified by X-ray spectroscopy(XPS) and X-ray diffraction(XRD) respectively. Through the understanding the physical and chemical variation of PLD deposited SCNT at different temperature condition, the best PLD deposition condition of SCNT for TF-SOFC was derived. Acknowledgment This work was supported by the Global Frontier R&D Program on Center for Multiscale Energy System funded by the National Research Foundation under the Ministry of Science, ICT & Future Planning, Korea (2012M3A6A7054855) References [1] M. Li et al., “A niobium and tantalum co-doped perovskite cathode for solid oxide fuel cells operating below 500 °c,” Nat. Commun., vol. 8, no. 5, pp. 1–9, 2017.

Bias voltage dependent structure and morphology evolution of magnetron sputtered YSZ thin film: a basic insight

YSZ thin films (YSZTFs) with controlled structure and morphology are desirable for low temperature solid oxide fuel cells (SOFCs). We report for the first time the bias voltage (40 V and 120 V) dependent structural and morphological evolution of YSZ thin films grown via radio frequency magnetron sputtering (RFMS) technique. The optimum sample was annealed at 600 °C to achieve an improved ionic conductivity. As-prepared YSZTFs were characterized using various analytical tools. Glancing angle x-ray diffraction (GAXRD) pattern of YSZTFs revealed the existence of non-columnar structure (cubic phases) with preferred growth along [200] lattice orientation. YSZTFs grown at 120 V displayed good homogeneity and uniformity (100 nm thick and crystallite size in the range of 10–12 nm) accompanied by large microstrain along [111] lattice orientation. The bias voltage dependent alterations in the morphology of YSZTFs (grain compactness, size, shape, distribution and surface roughness) were clearly manifested in the FESEM and AFM images. Raman and FTIR spectra of YSZTFs disclosed the formation of tetragonal and cubic phases. An in-depth data analyses suggested the successful incorporation of Yttria into the zirconia lattice. Annealed film exhibited improved polycrystallinity and evolved morphology. These achieved YSZTFs could be effective electrolyte for low temperature SOFC operation.

Fabrication and Characterization of YSZ/ScSZ Bilayer Electrolyte via Cold-Isostatic Pressing (CIP) Method for Intermediate Temperature-Solid Oxide Fuel Cell (IT-SOFC) Application

Solid oxide fuel cell (SOFC) technology has advanced significantly in the recent years, and now is an interest of many renewable energy-related industries to invest. However, the main issue of SOFC is the high operating temperature that negatively influence its performance. To reduce the temperature, a method of using bilayer electrolyte is proposed. In this study, a bilayer electrolyte of Yttria-stabilised Zirconia (YSZ) and Scandia-stabilized Zirconia (ScSZ) is used with the objective to reduce the temperature of SOFC to intermediate temperature ranges. ScSZ has been chosen as an alternative to YSZ due to its superior ionic conductivity and good mechanical properties. To achieve the objective, bilayer YSZ/ScSZ electrolyte has been fabricated at different compositions using cold-pressed method. This paper presents the fabrication and characterization results of the work.

Solid oxide fuel cell operation in a solid oxide fuel cell–internal combustion engine hybrid system and the design point performance of the hybrid system

A solid oxide fuel cell (SOFC)–internal combustion engine (ICE) hybrid system is a recently-proposed distributed electric power generation system to achieave extremely high efficiency beyond that of current technologies. The objectives of this study are to find the operation characteristics of the SOFC in the hybrid system and determine the operational design point of the hybrid system. To accomplish these objectives, operation of a 5 kW-class SOFC–ICE hybrid system was analysed by integrating the experimental results of the internal combustion engine with the simulation models of other system components. Two unique characteristics of SOFC operation were found and analysed. First, the SOFC in the hybrid system should utilize anode inlet gas with low temperature (e.g., 750–800 K) and low external reforming rate (e.g., 30–40%), which decreases the SOFC temperature, especially at the entrance, where the current density becomes very low, decreasing SOFC performance. Second, the overall effects of pressure pulsation caused by the engine on SOFC operation are insignificant since the flow path between the SOFC and the engine acts as a damper, reducing the pressure pulsation amplitude. The estimated variations were 0.2 mV in SOFC cell voltage. To determine the operational design point of the hybrid system, parametric analyses of system operation were conducted while varying several control parameters, e.g., SOFC fuel utilization factor. The design point of system operation was determined by considering system performance and operational stability. Near-zero pollutant emissions and 59.0% system efficiency were achieved at the determined design point, a 7.9% absolute and 15.5% relative improvement compared to that of an SOFC stand-alone system.

Enhanced Electrochemical Properties of Lu-doped BaCeO3 and KCl-NaCl Composite as Electrolyte for Intermediate Temperature Solid Oxide Fuel Cells

Enhanced Electrochemical Properties of Lu-doped BaCeO3 and KCl-NaCl Composite as Electrolyte for Intermediate Temperature Solid Oxide Fuel Cells

Perspective of perovskite-type oxides for proton conducting solid oxide fuel cells

Solid oxide fuel cell (SOFC) is one of the promising solid-state electrochemical device that converts chemical energy of varied fuels into electricity with high efficiency. However, its market acceptability is hindered due to its high operating temperature (800–1000 °C) that is dictated by the use of conventional oxide ion conducting yttria-stabilized zirconia electrolyte and sluggish oxygen reduction reaction properties of conventional Sr-doped LaMnO3 cathodes. Hence, major focus in the field of SOFCs has been directed towards reducing the operating temperature of current SOFCs to intermediate temperatures (500–700 °C), with the emphasis on material development for advanced electrolytes and cathodes. Due to the ease of doping on both A and B sites, structural stability, and ability to show both ionic (O2−, H+) and electronic conductivity, perovskite-type ABO3 (A = Sr, Ba; B = Ce, Zr) ceramics has been the focus of research towards development of proton conducting SOFCs (H-SOFCs). Despite significant developments, there is a general lack of understanding regarding future research directions in this field. In this review article, we first present an overview of crystal structure, dopant composition and its correlation with chemical stability and electrical conductivity followed by existing challenges associated with cathode development for H-SOFCs and achieving high fuel cell performance. We also outline the recent efforts directed towards reducing the H-SOFCs operating temperature.

The Sputtering of Heusler Alloy Catalyst onto the Porous Anode of the Intermediate Temperature Solid Oxide Fuel Cells for Ammonia Disassociation

In the past years, steam methane reforming (SMR) is a standard solution for the hydrogen production from hydrocarbon fuels for the development of commercial units of intermediate temperature solid oxide fuel cells (IT-SOFCs) systems. However, feeding methane as fuels can induce carbon deposition which would deteriorate the microstructure of the anode and endanger the lifetime of cells. As a result, ammonia becomes the alternative fuels for SOFCs since no residuals will be deposited onto the anode surface. The only concern of the ammonia fuels is the tentative formation of nickel-nitrogen (Ni3N) compound on the anode surface from recent reports. In this paper, Heusler alloy was deposited on the porous anode by sputtering to disassociate ammonia as the hydrogen sources and detour the possible pathways for Ni3N formation. The planar SOFCs is composed of anode-supported Ni-Sm0.2Ce0.8O2-δ (Ni-SDC) and the cathode of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) with the operation temperature of 650°C. The micro-scale material properties and the stability of crystalline of Heusler-SDC single cells will be examined for 10 hours tests.

Surface Modifications of Nano-Structured Cathodes to Enhance Durability of Intermediate Temperature Solid Oxide Fuel Cells

The bulk-to-surface Sr-segregation can seriously compromise the stability of oxygen electrocatalysis in Sr-doped perovskite oxides such as La1-xSrxCoO3-δ and La1-xSrxCo1-yFeyO3-δ and limit their practical applications as cathode materials in solid oxide fuel cells. This work aims to acquire fundamental knowledge of Sr-segregation process under practical conditions in solid oxide fuel cells and develop suppression method to ensure the long-term stability through surface modifications. In this work, the pristine and ZrO2 atomic layer deposition (ALD) modified La0.6Sr0.4CoO3- d (LSCo) epitaxial films were used as the model systems to investigate how the temperature, time and surface coating affect the surface concentration of Sr via in situ synchrotron-based ambient pressure XPS. This information was also correlated with their electrochemical performances characterized by electrochemical impedance spectroscopy. We also report a Sr-segregation-free SrCo0.9Ta0.1O3-δ (SCT) multifunctional coating on a benchmark cathode LSCF as a means of enhancing ORR activity and durability against Cr-poison.

Double Columnar Interlayer for Increased Cathodic Activity of Intermediate Temperature Solid Oxide Fuel Cells

Effects of double columnar structure interlayer film, in which tensile strain were introduced, on cathodic activity of SmCoO3 was investigated. Double columnar film of Pr2NiO4(PNCG)-Sm doped CeO2 (SDC), PrBaCo2O5.5-SDC, Sm0.6Sr0.4CoO3(SSC)- SDC, and La0.6Sr0.4FeO3-SDC were successfully prepared by PLD method and it was found that insertion of PNCG-SDC or SSC-SDC double columnar film decreased the overpotential of SSC cathode. The power density of the cell deposited on Ni-Fe porous metal substrate was higher than 3W/cm2 at 773K and impedance results suggested that the increased power density was explained by decreased cathodic overpotential. Increased diffusivity of oxide ion in double columnar film is effective for expanding reaction area resulting in the increased cathodic performance for oxide ion dissociation.

Thermodynamic Investigation and Optimization of a Power Generation System based Solid Oxide Fuel Cell using Taguchi Approach

Fuel cells directly convert chemical energy into electrical power using electrochemical reactions. Solid oxide fuel cell (SOFC) is one of the high-temperature fuel cells that propose a promising future from the standpoint of power generation. In this study, optimization of an SOFC system is performed using Taguchi approach after verification of the model in compare with experimental results. Current density, inlet temperature of SOFC, and utilization factor are considered as input parameters and the electrical power is selected as the output response. The analysis of variance (ANOVA) results indicate that the current density is the most effective parameter on electrical power which has 52% of contribution followed by inlet temperature of SOFC and utilization factor by 25 and 20% of contributions, respectively. The electrical power enhances by increasing current density and inlet temperature of SOFC and reducing utilization factor. Signal to noise ratio (S/N) analysis elucidate that the current density of 9500 A/m2, the inlet temperature of SOFC of 850 °C, and the utilization factor of 75% is the optimum condition in order to achieve the highest electrical power. The results show that the electrical power is 644.3 kW at the optimum condition.

Design and Analysis of S-CO2 Cycle and Radial Turbine for SOFC Vehicle Waste-Heat Recovery

Solid oxide fuel cell (SOFC) vehicles are considered to have broad prospects for development, and the high operating temperature of SOFC results in great potential for waste-heat recovery. Many concepts for utilizing waste heat of SOFC have been suggested and studied, and most of them directly couple an SOFC to a gas turbine, which require the SOFC to operate at an elevated pressure and make the system less flexible and thus harder to operate. In recent years, with the development of turbine and heat exchanger technology, the supercritical carbon dioxide (S-CO2) power cycle has raised widespread attractions for the waste recovery. This study explores the potential of S-CO2 Brayton cycle to realize waste-heat recovery for an SOFC vehicle. The SOFC can operate at atmospheric pressure, and the hybrid system is easier to operate than the directly coupled systems. In this paper, a simple recuperated S-CO2 Brayton cycle is proposed and the key component, radial inflow turbine is designed and focused. The flow state of the designed turbine is analyzed in detail based on computational fluid dynamics (CFD) numerical simulation. Five cases with different impeller tip clearances are numerically simulated to study its influence on the turbine performance. In addition, off-design performance analysis of the radial inflow turbine is conducted considering the temperature fluctuation of SOFC in practical applications.

Chemical synthesis of materials based on calcium zirconate for solid oxide fuel cells (SOFC)

AbstractFuel cells allow the production of energy from a clean electrochemical reaction. Among various types, the solid oxide fuel cell (SOFC) operates at high temperatures, allowing the conversion of hydrogen fuel into electricity, where water is generated as a by‐product. Strontium‐doped lanthanum manganite (La1‐xSrxMnO3, LSM) is commonly used as a cathodic material in traditional high‐temperature solid oxide fuel cells. Nowadays, the operating temperature of SOFCs should be reduced to 600–800°C due to improved fine electrolyte production techniques and the use of some intermediate temperature electrolytes. The LSM is not a suitable cathode for SOFCs operating in this temperature range, since it does not have a high enough conductivity and its electrochemical activity is very low as well. In this article, the performance improvement of LSM is described by mixing with calcium zirconate. The composite ceramic materials CaZrO3−La0.6Sr0.4MnO3, CaZrO3−NiO, and CaZrO3 were synthesized by combustion method, for application as a SOFC single cell. The results prove that the synthesized materials have potential to be used in a SOFC cell. At 800°C, was confirmed the CaZrO3 formation. Through Electrochemical impedance spectroscopy, the analysis presented low activation energy and the materials have been demonstrated to be compatible, an important fact to construct a suitable SOFC cell. The obtained activation energy was 0.90, 0.85, and 0.51 eV for the electrolyte, the anode and the cathode, respectively.