Solid Oxide Fuel Cell Applications Research Articles

A Review on Solid Oxide Fuel Cell Technology: An Efficient Energy Conversion System

The increasing global dependence on fossil fuels for energy has prompted researchers to explore alternative power generation sources that offer higher efficiency, cost-effectiveness, and low environmental impact. Developed countries have been making continuous efforts to reduce their reliance on depleting fossil fuel sources to curb carbon emissions. As a result, hydrogen has gained significant attention among researchers as a potential future fuel that meets all the necessary criteria. Many countries aiming for a hydrogen economy have invested in research on fuel cells. Among various fuel cells, the solid oxide fuel cell (SOFC) has emerged as a commercially viable power source at a small scale. This paper provides an extensive review of the components, materials, design, operation, and integration strategies of SOFCs with existing thermal-based power plants. The performance and prospects of various SOFCs in standalone and hybrid modes are summarized, along with the limitations. Additionally, the research and commercialization efforts that can enhance the potential applications of SOFCs as a sustainable and reliable system in the long term are outlined.

Co-precipitation process as an effective and viable route for proton-conducting solid oxide fuel cell applications

BaCe0.7Zr0.1Y0.1Yb0.1O3-δ (BCZYYb) is one of the most popular electrolyte materials in proton ceramic fuel cells (PCFCs). The synthesizing method and properties of BCZYYb powders have a significant impact on the sintering activity of electrolyte materials. In this work, the BCZYYb electrolyte was synthesized by ammonium bicarbonate co-precipitation method (CPT), and was compared with the powder produced by solid-state reaction (SSR) and sol-gel (SG) methods. XRD results show the BCZYYb powder synthesized by the CPT method belongs to orthorhombic crystal system with a space group of Pmcn (No. 62) and the refined lattice parameters are a = 8.774 Å, b = 6.173 Å, and c = 6.203 Å. In humid air atmosphere, the total conductivity at 650 °C and the activation energy for the BCZYYb powder prepared via the CPT method was 2.1 × 10−2 S cm−1 and 0.46 eV, respectively, as compared with 1.9 × 10−2 S cm−1 and 0.45 eV for the SSR method, and 1.8 × 10−2 S cm−1 and 0.44 eV for the SG method. Under similar testing conditions, the measured peak power densities were 0.51, 0.35, and 0.40 W cm−2 at 650 °C for the anode supported PCFCs using electrolyte powder prepared via CPT, SSR and SG methods, respectively, which proves the CPT method is an effective and viable route for PCFCs applications.

Cation doping and oxygen vacancies in the orthorhombic FeNbO4 material for solid oxide fuel cell applications: A density functional theory study.

The orthorhombic phase of FeNbO4, a promising anode material for solid oxide fuel cells (SOFCs), exhibits good catalytic activity toward hydrogen oxidation. However, the low electronic conductivity of the material specifically in the pure structure without defects or dopants limits its practical applications as an SOFC anode. In this study, we have employed density functional theory (DFT + U) calculations to explore the bulk and electronic properties of two types of doped structures, Fe0.9375A0.0625NbO4 and FeNb0.9375B0.0625O4 (A, B = Ti, V, Cr, Mn, Co, Ni) and the oxygen-deficient structures Fe0.9375A0.0625NbO3.9375 and FeNb0.9375B0.0625O3.9375, where the dopant is positioned in the first nearest neighbor site to the oxygen vacancy. Our DFT simulations have revealed that doping in the Fe sites is energetically favorable compared to doping in the Nb site, resulting in significant volume expansion. The doping process generally requires less energy when the O-vacancy is surrounded by one Fe and two Nb ions. The simulated projected density of states of the oxygen-deficient structures indicates that doping in the Fe site, particularly with Ti and V, considerably narrows the bandgap to ∼0.5eV, whereas doping with Co at the Nb sites generates acceptor levels close to 0eV. Both doping schemes, therefore, enhance electron conduction during SOFC operation.

Elucidation of the Transport Properties of Calcium-Doped High Entropy Rare Earth Aluminates for Solid Oxide Fuel Cell Applications.

Solid oxide fuel cells (SOFCs) are paving the way to clean energy conversion, relying on efficient oxygen-ion conductors with high ionic conductivity coupled with a negligible electronic contribution. Doped rare earth aluminates are promising candidates for SOFC electrolytes due to their high ionic conductivity. However, they often suffer from p-type electronic conductivity at operating temperatures above 500°C under oxidizing conditions caused by the incorporation of oxygen into the lattice. High entropy materials are a new class of materials conceptualized to be stable at higher temperatures due to their high configurational entropy. Introducing this concept to rare earth aluminates can be a promising approach to stabilize the lattice by shifting the stoichiometric point of the oxides to higher oxygen activities, and thereby, reducing the p-type electronic conductivity in the relevant oxygen partial pressure range. In this study, the high entropy oxide (Gd,La,Nd,Pr,Sm)AlO3 is synthesized and doped with Ca. The Ca-doped (Gd,La,Nd,Pr,Sm)AlO3 compounds exhibit a higher ionic conductivity than most of the corresponding Ca-doped rare earth aluminates accompanied by a reduction of the p-type electronic conductivity contribution typically observed under oxidizing conditions. In light of these findings, this study introduces high entropy aluminates as a promising candidate for SOFC electrolytes.

Structural and Electrochemical Performance of Sr0.9La0.1WO4 Electrolyte Materials for Solid Oxide Fuel Cells

A possible component of power generation technologies, solid oxide fuel cells (SOFCs) offer a high fuel-to-power conversion efficiency and no negative environmental impact. The solid-state sintering process was used to synthesize the scheelite-structured Sr0.9La0.1WO4 (SLW1) electrolyte material, and phase stability and ionic conductivity were evaluated for their technological applicability for SOFC applications. The resulting mixture, which was a single phase in a tetragonal crystal system, produced a scheelite structure of the space group I41/a. Its symmetry, space group, and structural characteristics are confirmed by X-ray diffraction (XRD) at room temperature and the Rietveld analysis that follows. A highly dense crystal structure was revealed by SEM examination. The ionic conductivity of the SLW1 sample is higher than SBW materials and lower than the conventional BCZY perovskite structure. At 900°C in both the wet Ar and dry Ar conditions, the SLW1 sample’s ionic conductivity was 2.41 × 10−5 S cm-1 and 1.76 × 10−5 Scm−1. This scheelite-like compound showed a thick microstructure and substantial conductivity, making it a potential mixed ion-conducting electrolyte for SOFC.

Theoretical Study of Electric, Dielectric, and Optical Properties in Ion Doped Multiferroic SrFe12O19 Nanoparticles.

Electric, dielectric, and optical (band gap) properties of pure multiferroic as well as La- and Ni-doped SrFe12O19 (SFO) (at different sites) are investigated using a microscopic model and Green's function technique. The concentration dependence of the polarization P is considered for substitution of rare earths ions on the Sr sites. For a small La ion doping concentration, x = 0.1, La-doped SFO is ferroelectric, whereas for a larger doping concentration, for example x = 0.5, it is antiferroelectric. The real part of the dielectric constant ϵ increases with an increasing magnetic field h. ϵ decreases with an increasing frequency and La dopants. Therefore, La-doped SFO is suitable for microwave application with a low dielectric constant. The magnetic properties of pure SFO NPs are also studied. Ni doping at the Fe site of SFO leads to enhanced ferroelectric polarization and dielectric constant. The band gap decreases or increases by substitution of Ni or In ions on the Fe site, respectively. The results reveal that the tuned band gap of Ni-doped SFO makes it a crucial candidate for optoelectronic and solid oxide fuel cell applications.

PrBaFe2O6-δ-based composites as promising electrode materials for protonic ceramic electrochemical cells

PrBaFe2O6–δ (PBF) is considered as a promising material for mixed ionic-electronic conductors used in high-temperature applications. In the present work, PBF was used as a basis for two chemical modification approaches, including doping with cobalt, nickel and copper, as well as composite design with the addition of a BaCe0.8Sm0.2O3–δ phase. The single-phase and composite materials were successfully prepared and characterized in terms of their functional properties. The two approaches were found to synergistically affect the functional properties of PBF, allowing a trade-off between thermomechanical and transport properties to be achieved. As a result, the prepared 70 wt% PrBaFe1.9M0.1O6–δ (M = Co, Ni, Cu) + 30 wt% BaCe0.8Sm0.2O3–δ composites exhibit acceptable electrochemical activity in the intermediate-temperature range. The best electrochemical activity was found for the sample with M = Cu, whose polarization resistance at 700 °C reaches 1.7 Ω cm2. Therefore, the designed PBF-based composites can be considered as promising electrode materials for solid oxide fuel cell applications.

Novel SOFC system concept with anode off-gas dual recirculation: A pathway to zero carbon emission and high energy efficiency

In recent years, the potential of Solid oxide fuel cell (SOFC) technologies as energy conversion devices with high efficiency and zero‑carbon emissions has been underestimated, where high fuel utilization plays a crucial role. Although the SOFC system with anode off-gas single recirculation has received much attention as a means to increase fuel utilization, this problem is not thoroughly addressed. To overcome this limitation, this paper proposes a novel SOFC system concept featuring anode off-gas “dual” recirculation, designed to maximize fuel utilization up to the theoretical limit of 100%. This innovative approach inherently eliminates carbon dioxide emissions through an integrated carbon capture process, thereby maintaining systematic carbon balance. A comparative analysis among the novel dual recirculation system, traditional single-pass, and other anode off-gas recirculation systems, reveals that the proposed system outperforms existing configurations. It achieves electrical and overall combined heat and power efficiencies of 49.6% and 85.7%, respectively, even after accounting for the energy required for carbon capture. This represents a 21.5% increase in electric efficiency over the single recirculation system, with a six-fold increase in tail-gas CO2 concentration, reaching 26.3%. The study categorizes the four analyzed systems into “open” or “closed” based on whether the anode off-gas is directly discharged into the environment. Systematic investigations into carbon deposition potential, fuel utilization, flow rate, operating voltage, carbon capture ratio, and condensation temperature disclose distinct patterns between open and closed systems. The closed configurations exhibit superior performance, suggesting they are more suitable for SOFC applications.

Defect-induced improved structural and electrical properties of Gd-Sr co-doped ceria for solid oxide fuel cell applications

Compositions of Ce1-x-yGdxSryO2-δ (x = 0.1, 0.2, and y = 0.025, 0.05, 0.075) are prepared using the sol-gel auto combustion method. The as-prepared powders are calcined at 500 °C for 2 h, followed by pelletization and sintering at 1450 °C for 4 h. Phase identification, defect distribution, microstructural analysis, and conductivity are examined using X-ray diffraction, Raman spectroscopy, scanning electron microscopy and impedance spectroscopy, respectively. A single crystalline phase is formed, and the lattice parameter variation with dopant concentration exhibits anomalous behavior. All the samples show relative densities higher than 92 %. The partial liquid phase sintering is also observed. In co-doped samples, the doping of 10 % Gd with 2.5 % Sr exhibits the highest conductivity, i.e., 1.20 × 10−2 S cm−1 at 600 °C. The developed materials are used in anode-supported cell testing. It shows a maximum power density of 112.7 mW cm−2 and a current density of 288.7 mA cm−2 at 600 °C with wet hydrogen and air on the anode and cathode side, respectively.

Comparative performance assessment of nano-composite cathode of LMSO-BSCMF for low temperature solid oxide fuel cell applications

Comparative performance assessment of nano-composite cathode of LMSO-BSCMF for low temperature solid oxide fuel cell applications

Development and performance evaluation of (Sm1-xNdx)0.2O2-δ electrolyte for low-temperature solid oxide fuel cell application

Major hurdle for SOFC operation at lower temperature is it’s ion migration through electrolyte crystal lattice reduces as more energy required and lowered number of ion vacancies. In order, researchers from all over the world trying to develop SOFC which operates at lower temperature which let to erupt the electrolyte performance. Currently available electrolyte YSZ (Yttria Stabilized Zirconia) shows high efficiency above 1100 °C. Fluorite structure doped/codoped ceria electrolyte shows better ionic conductivity below the 1000 °C. In current study ceria co doped with the Sm+3 and Nd+3 having ionic radius close to host ceria through oxalate co precipitation route. Crystallite size and structure is observed through X-ray diffraction for purity of doping with nano crystallite size transpose from 13.21 to 22.21 nm. Furthermore, Energy dispersive X-ray spectroscopy (EDXS) validates maximum 0.2 Codoping achieved through oxalate rought. Moreover grain size and grain boundary compaction enhances with sintering electrolyte pellet at 1300˚C for 2 h observed under FE-SEM. AC and DC conductive properties are studied with diverse codoping percentage and it is analyzed through Electrochemical Impedance Spectroscopy (EIS). Ce with 0.1 codoping Sm+3 and Nd+3 respectively enhances ion migration with minimum activation energy and relaxation time in lattice site.

Reactive Condensation of Cr Vapor on Aluminosilicates Containing Alkaline Oxides

The research presented herein is part of a larger project delving into the mechanisms and pathways for reactive condensation of Chromium (Cr) vapors in high-temperature (>500o C) environments. The overall goal of this research project is to improve fundamental understanding of reactive condensation pathways for chromium (Cr) vapors generated in high-temperature systems such as exhaust manifolds, steam turbines, boilers, or solid oxide fuel cells (SOFCs). Reactive evaporation of Cr from stainless steels commonly used in these systems is well-documented; however, the interactions between volatilized Cr species and surrounding interfaces during complex and dynamic system exposures is poorly understood. Understanding the interactions between volatilized Cr species and downstream components during operation is critical for improving system performance, environmental health, and safety as some condensed Cr forms toxic hexavalent Cr(VI) species. The focus of this study is on the effects of alkaline oxides present within the substrate material on reactive condensation mechanisms of Cr vapors. Studying the reaction mechanisms between Cr vapors and ceramic surfaces has direct application to SOFCs as these materials are widely used in the field. For example, alumina-silica glass-ceramics are used as sealants in SOFCs. These materials belong to the SiO2–Al2O3 system and contain different compositions of oxides including CaO, Na2O, MgO, K2O, B2O3, Y2O3, and BaO. Another sealing material used in SOFCs is mica, a class of silicate minerals that forms into distinct layers. Two types of mica commonly used in SOFC applications are muscovite (potassium aluminum silicate hydroxide fluoride, KAl2(AlSi3O10)(F,OH)2), and phlogopite (potassium magnesium aluminum silicate hydroxide, KMg3(AlSi3O10)(OH)2). The specific research objective is to explore the effects of alkaline oxide additives in aluminosilicates on Cr collection and speciation. To accomplish this objective, an experimental platform was designed to assess interactions between samples of high-temperature steel alloys or Cr oxide (Cr2O3) powder with ceramic insulating materials. The chemical composition of the insulating materials used in this study range from pure silica (SiO2) and alumina (Al2O3) to combinations thereof with and without inclusions of alkaline earth metals (e.g., Ca, Mg). Preliminary results show three- to four-fold increases in Cr(VI) formation on silica fibers with weight percentages of ~30 and ~40 percent alkaline oxides (CaO and MgO), respectively, after exposure to volatile Cr species, relative to low-alkaline silica. Figure 1 presents an overview of the experimental concept, Cr(VI) test kit, and preliminary results for dependency on alkaline oxide content. Figure 1

Facile and Low Temperature Synthesis of Nd1.8Sr0.2NiO4-δ Cathode Nanofibers for Intermediate Temperature Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) are usually operated at high temperatures (800-1000 °C). As the overall efficiency of SOFC is governed by thermodynamics and kinetics during operation, reducing the operating temperature to 500-650 °C causes significant increase in the electrode polarization losses especially at cathode due to high activation energy towards oxygen reduction reaction (ORR) at cathode, which eventually reduces the overall cell performance. Addressing increased polarization losses at relatively low temperatures (500-650 °C) has been the key issue and a focus of many groups over past couple of decades. Conventional cathode materials lose their ORR activity and so discarded for intermediate temperature (IT)-SOFC application. In this regard, mixed ionic-electronic conductors (MIECs) offer high thermal and chemical stability along with high oxygen diffusion and good electronic conductivity at IT [1,2]. In addition, Ruddlesden-Popper (RP) type MIECs with A2BO4 structure have been demonstrated as promising cathode for IT- SOFCs due to their unique structure, rapid oxygen surface exchange kinetics, and excellent stability in atmosphere. Particularly Nd2NiO4+δ oxides offer an excellent oxygen diffusion coupled with high surface exchange coefficients and comparable thermal expansion coefficients with those of oxygen-ion conductors (YSZ and CGO) [2]. Enhanced electronic conductivity and electrochemical performance have been demonstrated for partial replacement of Nd with Sr in our previous reports [3].Albeit, the intrinsic material properties such as electrochemical catalytic activity and electrical conductivity are of primary importance, an actual electrode performance strongly depends on its microstructure. Therefore, in addition to using high catalytic and conductive materials, achieving an extremely high-power density, thus, requires a finely controlled electrode microstructure, to expand the electrochemically active triple-phase boundary (TPB). Recently, electrospinning has been considered as an efficient, cost effective and promising method for synthesis of ceramic nanofibers. Pertinent literature suggests that SOFC with cathode nanofiber has superior/better performance (nearly doubled power density and significant reduced polarization resistance) compared to powder type electrodes. Selection of suitable cathode materials with modified microstructure (nanofibers) would facilitate more electrochemically active sites for the oxygen reduction at relatively low temperatures <650 °C.In this paper we synthesized Nd1.8Sr0.2NiO4-δ (NSNO) cathode nanofibers using electrospinning technique and compared its electrochemical performance with NSNO nanopowder. Practically, 10 wt.% Polyvinylpyrrolidone (PVP) solution was prepared by dissolving it in ethanol, to which stoichiometric amounts of Nd-nitrate, Sr-nitrate, Ni-nitrate (total weight percentage of metal salts- 3 wt%) were added, together with some deionized water. The mixture was then stirred for 10 h at room temperature on a magnetic stirrer to obtain a homogeneous sol. The sol was loaded into the electrospinning syringe. Distance between the spinneret and the collector was fixed at 25 cm and the high-voltage supply was maintained at 30 kV. The spinning rate was controlled at 5 ml h- 1 by a syringe pump. The obtained nanofibers were dried at 80 °C for 12 h, then sintered at 900 °C for 2 h in air to obtain single-phase NSNO.The obtained nanofibers were characterized using room temperature XRD, XPS, SEM and dc electrical conductivity (400-650 °C). In addition, electrochemical impedance spectroscopy studies on symmetric cells were carried out as a function of temperature (400-650 °C). Improved electrochemical performance is attributed to enhanced electrochemical active sites for ORR due to nanofibers and optimum porosity.

Development of BSCMF system of cathode materials and fabrication of symmetrical cell (BSCMF/GDC/BSCMF) for low temperature solid oxide fuel cell applications

ABSTRACT In the present work, cathode materials of Ba0.5Sr0.5(Co1-xMgx)0.2Fe0.8O3 system (x = 0, 0.2, 0.4, 0.6, 0.8, 1) have been produced and the effect of magnesium (Mg) doping level on cathode performance with Gadolinium doped Cerium (GDC) electrolyte was investigated. The polarisation resistance (RP) for cathode symmetric cells was measured from 600°C to 700°C under open circuit state. At 700 °C, the polarisation resistance of BSCF is 13.96 ohm-cm2 and with the addition of Mg it has decreased to 5.17 ohm-cm2. Further increase in the Mg concentration decreased the polarisation resistance up to 0.34 ohm-cm2, which is the minimum value obtained in the composition BSCMF8. It is observed that charge transfer (CT) is more in the case of Mg-rich compositions. With the increase of magnesium concentration in the cathode, RP value was observed as decreased. This is due to the high oxygen permeation flux behaviour of magnesium, which is in the B-site of the cathode. The coefficient of thermal expansion (CTE) of BSCF is measured to be 22.1 × 10−6/K and decreased to 17.45 × 10−6/K with Mg addition in the composition to BSCMF8, due to the constant oxidation state of Mg by which it suppressed the chemical expansion caused by Co.

Role of Divalent Co-Dopant as Structure Stabilizer in Scandia-Stabilized Zirconia Electrolyte for SOFC

The present investigation reports the role of divalent binary co-dopant (Ca2+) in 11 mol% scandia stabilized zirconia (11SSZ) electrolytes to resolve its severe long-term aging issue for application in solid oxide fuel cells (SOFC). Dense electrolytes were formulated via the solid-state reaction method and their crystal structure was identified by X-ray diffractometer (XRD). To examine total electrical conductivity and its stability in oxidizing and reducing atmosphere DC four-point probe measurement was used. Among all the compositions, 0.2Ca11SSZ demonstrates the highest conductivity of 0.075 S cm−1 at 800 °C, with excellent stability of 6.7%/100 h in a reducing (97 vol% H2/3 vol% H2O) atmosphere. However, the presence of 0.5 mol% calcium in 11SSZ results in more than threefold suppression of aging rate compared to undoped11SSZ i.e. 2.19%/200 h in air atmosphere at 800 °C. Additionally, the doping of divalent Ca2+ widens the electrolytic domain up to pO2 ∼ 10−26 atm at 1000 °C compared to state-of-art 8YSZ (pO2 ∼ 10−22 atm), with 0.024% linear expansion on phase transition and 172 MPa flexural strength. Convincingly, the excellent structure stability and ionic conductivity of calcium co-doped 11SSZ compared to state-of-the-art electrolytes make them potential candidates to be used as an electrolyte for SOFC application.

Investigation of alumina- and scandia-doped zirconia electrolyte for solid oxide fuel cell applications: Insights from broadband impedance spectroscopy and distribution of relaxation times analysis

Zirconia based oxygen conductors are state of the art solid electrolytes used for solid oxide fuel cell applications. In this study, we investigated zirconia double-doped with aluminium and scandium oxide. The Al0.04Sc0.06Zr0.9O1.95 electrolyte was prepared using Pechini method. In the 300–800 K temperature range, this material's structure is cubic with a fraction of monoclinic modification, while above 800 K it becomes completely cubic. The ceramic form of Al0.04Sc0.06Zr0.9O1.95 electrolyte was investigated using broadband impedance spectroscopy, utilizing equivalent circuit analysis and distribution of relaxation times (DRT) technique. The high-frequency relaxation process's complexity observed in the spectra's DRT representation at temperatures up to 500 K was associated with the two zirconia phases. The Al0.04Sc0.06Zr0.9O1.95 electrolyte was tested in a hydrogen-oxygen laboratory solid fuel cell in the temperature range 973–1123K. Understanding the fundamentals of the relaxation processes is necessary to increase the durability of the ceramic electrolyte in the fuel cell.

Glass-diopside composite sealing material for planar solid oxide fuel cells

Sealants based on glass have been widely used in solid oxide fuel cell (SOFC), and have shown considerable potentials due to their low leakage rate. We report a tape of sealant made by adding different contents of diopside into silicate glass, which has a coefficient of thermal expansion (CTE) matching that of adjacent components. Glass-diopside composite sealing material can block the diffusion of chromium from interconnect has been studied. The structure of the 20 wt% diopside doped silicate glass is stable at high temperatures with leakage rates less than 0.004 sccm∙cm−1, and no crystal except for diopside is found in XRD analysis after heating at 750 °C for 100 h. Excellent interface compatibility between the sealant and SUS430 interconnect was proved by SEM at 750 °C for 100 h. The above results prove the possibility of using glass-diopside composite sealing material for SOFC applications.

Thin film Si solar cell and solid oxide fuel cell technologies for a low cost, environmentally friendly and sustainable source of energy

Thin-film solar cell technology based on hydrogenated amorphous silicon has matured over the last two decades and is capable to deliver commercial modules with almost 10 % stabilized efficiency. Moreover attention on hydrogen fuel cells is increasing as the range of potential commercial applications expands, with more than 3800 fuel cell systems being installed and operated worldwide. These systems attain high theoretical efficiencies in the range of 43.7-70.4 %, with an additional 20% as heat recovery, and operating at carbon-free conditions between 50 °C and 900 °C. In this paper the status of thin-film silicon solar cell technology is reviewed by comparing it to other major solar cell technologies. A discussion is also made upon the benefits obtained from the few potential applications, as long-term potential actions for sustainable development, and the future of Solid Oxide Fuel Cells (SOFCs). Applications of thin-film silicon modules and SOFCs are presented. EPIA (European Photovoltaic Industry Association) estimates that half of the growth in the next two years will come from thin-film technology.

Investigating the physico-chemical and electrochemical properties of various aliovalent cations doped ceria powders for electrolytic applications in solid oxide fuel cells

Solid oxide fuel cells (SOFCs) are one of the most efficient energy conversion devices, yet their high operating temperatures have caused a bottleneck towards their commercialization. Due to sufficient conductivity and stability below 600 °C, doped ceria is under investigation for electrolytic applications in SOFCs. During this study, starting with Ce0.8Sm0.2O2-δ, 5% of Sm3+ was replaced by dopants of varying valencies and sizes giving Ce0.8Sm0.15X0.05O2-δ (where X = Bi3+, Mg2+, Li+), thereby aiming to keep the total dopant concentration constant. The structure-property relationship was studied using a number of techniques including XRD, Raman spectroscopy, FTIR spectroscopy and temperature dependent EIS. XRD indicated the presence of a minor phase belonging to MgO for the Mg2+ co-doped sample. Raman spectroscopy showed the presence of δ-Bi2O3 for Bi3+ doped SDC. Based on the quantitative analysis of Raman data we concluded that the materials were multi-phasic and co-dopants addition did not have a noticeable influence especially on defect concentration. In EIS data, measured from of 550–750 °C, change in conductance behavior was shown by Arrhenius plots for SCB and SCM when the test temperature was raised over 650 °C, possibly reflecting the combined conduction due to the additional phases along with SDC for these samples. Poor solubility of the non-rare earth metal ions into the ceria lattice was observed. This study suggests the need of a comprehensive analysis of doping mechanism preferably by synchrotron-based techniques to effectively incorporate low-cost non-rare earth metals into ceria lattice.

Development of conducting Bi0.5Sr0.5FeO3–δ-Gd0.1Ce0.9O2–δ composite cathodes for IT-SOFCs

Decreasing the working temperature of solid oxide fuel cells (SOFCs) to 400 °C–600 °C is a primary concern for current fuel cell research. Unfortunately decrease in operating temperatures leads to increase in cathode polarization, which deteriorates electrochemical activity of the cathode for oxygen reduction reaction (ORR). Consequently, the search of new cathode materialsis one of the critical bottle-neck towards the development of intermediate-temperature SOFCs (IT-SOFCs). In this study, we have successfully synthesized Bi0.5Sr0.5FeO3-δ and Bi0.5Sr0.5FeO3-δ-Gd0.1Ce0.9O2-δ((1-x) BSFO-xGDC) composite cathodes with varying compositions (x = 50, 40, 30, and 20wt%). The crystal structure, microstructure, electrochemical properties and performance stability of these composite cathodes have been comprehensively evaluated using techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Our results demonstrate that the introduction of Gd0.1Ce0.9O2-δ( GDC) has a significant impact on the electrochemical performance of the composite cathodes. Among the different compositions studied, the cathode with a composition of x = 70 wt% exhibits particularly promising electrochemical properties. The electrode resistance polarization of 70BiSFO-30GDC is 0.39 Ωcm2 and 0.8 Ωcm2 for symmetrical and half-cell at 600 °C. The preliminary results of this study reveal that the 70BiSFO-30GDC composite cathode demonstrates remarkable ORR activity. Further investigations and comprehensive analyses are warranted to validate and explore the full potential of the 70BiSFO-30GDC composite cathode in the context of SOFC applications.