Ce0.9Gd0.1O1.95 supported La0.6Sr0.4Co0.2Fe0.8O3−δ cathodes for solid oxide fuel cells

Lanthanum-based iron- and cobalt-containing perovskite has a high potential as a cathode material because of its high electro-catalytic activity at a relatively low operating temperature in solid oxide fuel cells (SOFCs) (600–800). To enhance the electro-catalytic reduction of oxidants on La_0.6Sr_0.4Co_0.2Fe_0.8O_3?δ (LSCF), Ga doped ceria (Ce_0.9Gd_0.1O_1.95, GDC) supported LSCF (15LSCF/GDC) is successfully fabricated using an impregnation method with a ratio of 15 wt% LSCF and 85 wt% GDC. The cathodic polarization resistances of 15LSCF/GDC are 0.015 Ω cm², 0.03 Ω cm², 0.11 Ω cm², and 0.37 Ω cm² at 800 °C, 750 °C, 700 °C, and 650 °C, respectively. The simply mixed composite cathode with LSCF and GDC of the same compositions shows 0.05 Ω cm², 0.2 Ω cm², 0.56 Ω cm², and 1.20 Ω cm² at 800 °C, 750 °C, 700 °C, and 650 °C, respectively. The fuel cell performance of the SOFC with 15LSCF/GDC shows maximum power densities of 1.45 W cm^?2, 1.2 W cm^?2, and 0.8 W cm^?2 at 780 °C, 730 °C, and 680 °C, respectively. GDC supported LSCF (15LSCF/GDC) shows a higher fuel cell performance with small compositions of LSCF due to the extension of triple phase boundaries and effective building of an electronic path.     

Electrophoretic deposition of La0.6Sr0.4Co0.8Fe0.2O3−δ cathodes on Ce0.9Gd0.1O1.95 substrates for intermediate temperature solid oxide fuel cell (IT-SOFC)

Porous thick films of La_0.6Sr_0.4Co_0.8Fe_0.2O_3?δ (LSCF) on Ce_0.9Gd_0.1O_1.95 (CGO) substrates were prepared by the electrophoretic deposition (EPD) method. Organic suspensions of different compositions containing LSCF ceramic particles were investigated with the aim to determine the optimal composition of the suspension and EPD conditions. Stainless steel substrates were used in order to determine the optimal parameters for the EPD process. The best results were achieved with solutions containing acetylacetone, iodine and starch. The EPD conditions leading to uniform LSCF films were: applied voltage 20 V and deposition time 120 s, with the electrodes separated 1.5 cm. EPD was also demonstrated to be a simple and useful method for making porous LSCF cathodes on CGO substrates. It was shown that the microstructure of the films can be controlled by changing the applied voltage, deposition time and concentration of additives in suspension.     

Electro-spinning Pr0.4Sr0.6Co0.2Fe0.7Nb0.1O3−δ nanofibers infiltrated with Gd0.2Ce0.8O1.9 nanoparticles as cathode for intermediate temperature solid oxide fuel cell

Pr_0.4Sr_0.6Co_0.2Fe_0.7Nb_0.1O_3−δ (PSCFN) nanofibers and their corresponding Pr_0.4Sr_0.6Co_0.2Fe_0.7Nb_0.1O_3−δ–Gd_0.2Ce_0.8O_1.9 (PSCFN–GDC) composites have been synthesized and applied as cathodes for intermediate temperature solid oxide fuel cells (IT-SOFCs). In this paper, PSCFN nanofibers were obtained through electro-spinning and the following pyrolysis process. The resultant PSCFN nanofibers were infiltrated with GDC precursor to prepare nanofiber-structured PSCFN–GDC composite cathodes. The optimal PSCFN: GDC mass ratio of 1: 0.10 was identified to possess the lowest interfacial polarization resistances of 0.264, 0.155, 0.039 and 0.018 Ω cm² at 650, 700, 750 and 800 °C, respectively, lower than those of the PSCFN–GDC nanoparticle-structured composite cathode. The PSCFN–GDC (1: 0.10) shows an excellent stability of electrochemical activity under a current density of 200 mA cm⁻² for 100 h at 800 °C. All results proved that the nanofiber-structured PSCFN–GDC composite could act as a highly efficient cathode candidate for the IT-SOFCs.     

Nanofiber-structured Pr0.4Sr0.6Co0.2Fe0.7Nb0.1O3-δ-Gd0.2Ce0.8O1.9 symmetrical composite electrode for solid oxide fuel cells

In this research, nanofiber-structured Pr_0.4Sr_0.6Co_0.2Fe_0.7Nb_0.1O_3-δ (PSCFN) electrode scaffolds were impregnated with Gd_0.2Ce_0.8O_1.9 (GDC) nanoparticles to prepare PSCFN-GDC nanofiber-structured composite electrodes, which could function well as a novel electrode material for symmetrical solid oxide fuel cells (SSOFCs). The polarization resistances of PSCFN-GDC (1:0.56) composite electrodes as cathode and anode were 0.044 and 0.309 Ω cm² at 800 °C, respectively, indicating that the composite electrodes demonstrated excellent electrochemical performances for both oxygen reductions and fuel oxidation reactions. La_0.8Sr_0.2Ga_0.8Mg_0.2O_3-δ (LSGM) electrolyte-supported single cells with the PSCFN-GDC symmetrical composite electrodes showed excellent long-term stability in wet H₂ (97% H₂-3% H₂O) and wet CH₄ (97% CH₄-3% H₂O) for 100 h with constant current density at 800 °C. A conversion electrode method was applied by interchanging the atmosphere of cathode and anode to solve the problem of PSCFN-GDC symmetrical single cell's carbon deposition in wet CH₄. After working three cycles for 384 h, carbon deposition was not found in the symmetrical electrode scaffold. Taken together, the results described above demonstrated that the PSCFN-GDC composite material acted as a promising symmetrical electrode for SSOFCs, and the conversion electrode method would make for a good application to process carbon deposition generated by hydrocarbon fuels.     

Microstructure anisotropy of La0.6Sr0.4Co0.2Fe0.8O3-δ film on rigid Gd0.1Ce0.9O1.95 substrate during constrained sintering

La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) cathodes on rigid Gd_0.1Ce_0.9O_1.95 (GDC) substrate were sintered to different densities, and their three dimensional (3D) microstructures were characterized using focused ion beam-scanning electronic microscopy (FIB-SEM) tomography. The microstructure anisotropies of the green and constrainedly sintered cathodes were studied using 3D mean intercept length (MIL) method and the two dimensional (2D) best-fit ellipse method and 3D best-fit ellipsoid method. It shows that in the constrained sintering of LSCF films, the microstructures were transversely isotropic in the plane parallel to the substrate, while the microstructures in the thickness direction were anisotropic. Density and grain size gradients were observed and quantified along the cathode thickness direction during constrained sintering. The pores were preferentially oriented and elongated in the thickness direction. The anisotropy factor increased as increasing the sintering time or sintering temperature in the current density range. Cross-sectional 2D measurements underestimated the pore anisotropy, but showed qualitative agreement with 3D measurements.     

Mechanical behavior of ferroelastic porous La0.6Sr0.4Co0.2Fe0.8O3−δ prepared with different pore formers

The present work investigated the mechanical behavior of porous La_0.6Sr_0.4Co_0.2 Fe_0.8O_3−δ LSCF under uniaxial compression. The porous (LSCF) samples with the same grain size but different porous structures with 1.5–41% of porosity were prepared using three different pore formers. All the samples had ferroelastic domains and exhibited ferroelastic mechanical behaviors under uniaxial compression. Initial and loading moduli as well as critical stress monotonically decreased and remnant strain increased with increasing the porosity. The initial modulus can be determined by the actual porosity regardless of porous structure or grain size, whereas the other properties were more sensitive to experimental condition such as loading rate and maximum applied stress. Compressive fracture strength could be significantly influenced by porous structure.     

Semiconductor ionic based Sm0.2Ce0.8O2−δ-La0.6Sr0.4Fe0.8Cu0.2O3-δ heterostructure for low temperature ceramic fuel cells

Structural design/doping strategy is an efficient method to prepare electrolytes with high oxygen ionic conductivity, but there is still hindrance for solid oxide fuel cell (SOFC) commercialization. Recent advances in semiconductor ionic materials have developed a novel strategy in designing low-temperature electrolyte materials. Here, a heterostructure composite of LSFC (La_0.6Sr_0.4Fe_0.8Cu_0.2O_3-δ) and SDC (Sm_0.2Ce_0.8O_2?δ) is developed. The LSFC-SDC composite exhibits a high ionic conductivity, >0.1S/cm at 550 °C. With symmetrical NCAL (Ni_0.8Co_0.15Al_0.05LiO_2-δ)-coated electrode, cells with SDC-LSFC electrolyte exhibit high open-circuit voltage (OCV), and achieve a significant power improvement (>1000 mW/cm²) compared with pure SDC electrolyte at 550 °C. The short-term stability result has proven the operating ability of SDC-LSFC electrolyte under fuel cell environment (H₂/air). This work demonstrates a new developing route of low-temperature solid oxide fuel cell (LTSOFC), which is different from the conventional SOFC.     

Mechanical properties of LSCF (La0.6Sr0.4Co0.2Fe0.8O3−δ)–GDC (Ce0.9Gd0.1O2−δ) for oxygen transport membranes

In this study, for application in oxygen transport membranes, an LSCF (La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ)–GDC (Ce_0.9Gd_0.1O_2−δ) composite was manufactured, and its mechanical properties were studied. Generally, it is known that LSCF has a nonlinear modulus due to changes in its microstructure when a critical stress is loaded. To improve the mechanical properties of this material, which has a perovskite structure, a study was conducted to evaluate whether its properties change according to the rule of mixtures when it is formed into a composite with GDC. The results showed that the nonlinearity of the modulus of the composite for each specimen composition was largely reduced and stable under fatigue loading. The fracture toughness was superior to that of the LSCF (1.05 MPa m^1/2) or GDC (1.28 MPa m^1/2) monolithic materials when the composites (1.63 MPa m^1/2) was manufactured. The mechanisms for these were explained by finite element analysis and the observation of crack propagation. It was also confirmed that when these composite materials are used for oxygen transport membranes, they show stable properties.     

Characterization of La0.58Sr0.4Co0.2Fe0.8O3−δ–Ce0.8Gd0.2O2 composite cathode for intermediate temperature solid oxide fuel cells

La_0.58Sr_0.4Co_0.2Fe_0.8O_3?δ–Ce_0.8Gd_0.2O₂ (LSCF–GDC) composite cathodes with various weight ratios 90%, 70% and 50% of LSCF were prepared. Mechanical properties, thermal expansion properties and electrical properties were measured for potential applications in solid oxide fuel cells (SOFCs) with graded cathodes. LSCF and GDC as pure cathode and electrolyte materials were characterized as reference. The absence of new phases as confirmed by X-ray diffraction (XRD) analysis demonstrated the excellent compatibility between the cathode and electrolyte materials. Mechanical properties such as hardness and fracture toughness were measured by the micro-indentation technique, while hardness and elastic modulus were measured by the nano-indentation technique. Thermal expansion behavior was recorded by a dilatometer. Electrical conductivity was measured by the four probe DC method. The 50% LSCF–GDC composite has the lowest relative density among all the samples. Thermal expansion coefficients (TECs) and electrical conductivity increased with addition of LSCF contents in the composite, while mechanical properties depended more on the density than the LSCF content.     

High-performance LaNi0.6Fe0.4O3-δ-La0.45Ce0.55O2-δ nanoparticles co-loaded oxygen electrode for solid oxide steam electrolysis

Hydrogen production through solid oxide electrolysis cells (SOECs) driven by renewable energy has attracted a lot of attention. Nevertheless, the poor performance of the oxygen electrode is a bottleneck in the implementation of SOECs. This work reports a high-performance LaNi_0.6Fe_0.4O_3-δ-La_0.45Ce_0.55O_2-δ (LNF-LDC) nanoparticles co-loaded (La_0.8Sr_0.2)_0.9MnO_3-δ-Y_0.15Zr_0.85O_2-δ (LSM-YSZ) oxygen electrode. Firstly, the co-synthesized LNF-LDC nano-composite is characterized by XRD, SEM, H₂-TPR and O₂-TPD techniques. Compared with individually synthesized LaNi_0.6Fe_0.4O_3-δ (LNF), the co-synthesized LNF-LDC nanoparticles have a larger amount of oxygen vacancy and higher oxygen mobility due to a strong synergistic effect. Secondly, the LNF-LDC nanoparticles co-loaded oxygen electrode exhibits a higher electrochemical performance than the single LNF loaded LSM-YSZ electrode. Under 800 °C and 50% A.H., the cell with LSM-YSZ@LNF-LDC-4 μL delivers ?1.18 A cm^?2 at 1.3 V, which is 2.03 times higher than the cell with LSM-YSZ@LNF-4 μL. Therefore, co-loading LNF-LDC is a promising method to develop a highly efficient oxygen electrode for solid oxide steam electrolysis.     

Evaluation of (Ba0.5Sr0.5)0.85Gd0.15Co0.8Fe0.2O3−δ cathode for intermediate temperature solid oxide fuel cell

A perovskite-type (Ba_0.5Sr_0.5)_0.85Gd_0.15Co_0.8Fe_0.2O_3?δ (BSGCF) oxide has been investigated as the cathode of intermediate temperature solid oxide fuel cells (IT-SOFCs). Coulometric titration, thermogravimetry analysis, thermal expansion and four-probe DC resistance measurements indicate that the introduction of Gd³⁺ ions into the A-site of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3?δ (BSCF) leads to the increase in both oxygen nonstoichiometry at room temperature and electrical conductivity. For example, the conductivity of BSGCF is 148 S cm^?1 at 507 °C, over 4 times as large as that of BSCF. Furthermore, the electrochemical activity toward the oxygen reduction reaction is also enhanced by the Gd doping. Impedance spectra conducted on symmetrical half cells show that the interfacial polarization resistance of the BSGCF cathode is 0.171 Ω cm² at 600 °C, smaller than 0.297 Ω cm² of the BSCF cathode. A Ni/Sm_0.2Ce_0.8O_1.9 anode-supported single cell based on the BSGCF cathode exhibits a peak power density of 551 mW cm^?2 at 600 °C.     

Enhanced oxygen reduction reaction activity and electrochemical performance of A-site deficient (La0.6Sr0.4)1-xFe0.8Ni0.2O3−δ cathode for solid oxide fuel cells

In this work, (La_0.6Sr_0.4)_0.9Fe_0.8Ni_0.2O_3-δ (LSFN90), a stable, highly ORR-active and cost-efficient perovskite oxide, is developed as cathode materials for solid oxide fuel cell (SOFC). The introduction of A-site deficiency results in the crystal expansion of the cubic perovskite phase and an increase in oxygen vacancy concentration at operating temperature. The LSFN90 cathode displays good oxygen reduction reaction activity and low polarization resistance values. The A-site deficiency facilitates the diffusion of oxygen ions in the electrode and accelerates the surface oxygen exchange reaction. LSFN90 is used as cathode materials for SOFC to prepare anode-supported single cells, achieving maximum power densities of 1.51, 1.27, 0.95 and 0.63 W cm⁻² under wet hydrogen (3%H₂O–97%H₂) atmosphere at 850, 800, 750 and 700 °C, respectively. The introduction of A-site deficiency can greatly enhance the oxygen reduction reaction activity and electrochemical performance of the cathode, demonstrating that LSFN90 has significant potential as a cathode material for practical applications in solid oxide fuel cells.     

Oxygen permeation through dense La0.1Sr0.9Co0.8Fe0.2O3−δ perovskite membranes: Catalytic effect of porous La0.1Sr0.9Co0.8Fe0.2O3−δ layers

The oxygen permeation performance of a number of La_0.1Sr_0.9Co_0.8Fe_0.2O_3−δ (LSCF1982)-based membranes, consisting of dense LSCF1982 layer with/without porous LSCF1982 layer, was analyzed on the basis of the thickness of the dense layer and catalytic effect of the porous layer. A 0.27 mm thick dense membrane gives oxygen permeation flux ($J_{O_2}$) of 2.33 sccm min⁻¹ cm⁻² at 900 °C, which is increased to 3.55 sccm min⁻¹ cm⁻² on applying a porous layer of LSCF1982 onto the dense membrane. The membrane gives a stable flux for 300 h. The flux was further improved by reducing the thickness of the dense LSCF1982 layer and at 950 °C a flux of 4.47 sccm min⁻¹ cm⁻² is obtained with 0.012 mm thick membrane.     

Enhanced sintering of Ce0.8Nd0.2O2−δ-La0.8Sr0.2Ga0.8Mg0.2O3−δ using CoO as a sintering aid

Ce_0.8Nd_0.2O_1.9 (NDC) and La_0.8Sr_0.2Ga_0.8Mg_0.2O_3-δ (LSGM) electrolytes were prepared using a sol-gel method. NDC-LSGM composite electrolytes were subsequently prepared by adding 5% (w, mass fraction) precalcined LSGM powders to NDC sols. The electrolyte materials of NDC-Co and NDC-LSGM-Co were obtained by adding 1 mol% CoO to NDC sols and NDC-LSGM composite electrolytes, respectively. The microstructure and phase composition of the pellets were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectroscopy (EDS). The electrical conductivities of the pellets were measured using alternative current (AC) impedance spectroscopy. The results indicate that a single perovskite phase is observed for the LSGM ceramic, while NDC-Co, NDC-LSGM and NDC-LSGM-Co have a cubic fluorite structure similar to that of NDC. As a sintering aid, CoO can further promote grain growth and increase relative density (＞95%) of the NDC-LSGM composite electrolyte. The enhancement of the total conductivity is primarily attributed to the large increase in the conductivity of the grain boundary. However, the slight decrease of the grain boundary conductivity of the NDC-LSGM-Co electrolyte is caused by the presence of trace amounts of impurity phases in the grain boundaries.     

Improved electrochemical activity of Bi0.5Sr0.5FeO3-δ–Ce0.9Gd0.1O1.95composite cathode electrocatalyst for solid oxide fuel cells

Developing MIEC materials with high electrocatalytic performance for the ORR and good thermal/chemical/structural stability is of paramount importance to the success of solid oxide fuel cells (SOFCs). In this work, high-activity Bi_0.5Sr_0.5FeO_3-δ-xCe_0.9Gd_0.1O_1.95 (BSFO-xGDC, x = 10, 20, 30 and 40 wt%) oxygen electrodes are synthesized, and confirmed by XRD, SEM and EIS, respectively. The crystal structure, microstructure, electrochemical property and performance stability of the promising BSFO-xGDC composite cathodes are systematically evaluated. It is found that introducing GDC nanoparticles can obviously improve the electrochemical property of the porous composite electrode. Among all these composite cathodes, BSFO-30GDC composite cathode shows the best ORR activity. The peak power density of anode supported single cells employing BSFO-30GDC composite cathode reaches 709 mW cm^?2 and the electrode polarization resistance (R_p) of the BSFO-30GDC is about 0.14 Ω cm² at 700 °C. The analysis of the oxygen reduction kinetic indicates that the major electrochemical process of the GDC-decorated composite cathode is oxygen adsorption-dissociation. These preliminary results demonstrated that BSFO-30GDC is a prospective composite cathode catalyst for SOFCs because of its outstanding ORR activity.     

Effects of mass fraction of La0.9Sr0.1Cr0.5Mn0.5O3-δ and Gd0.1Ce0.9O2-δ composite anodes for nickel free solid oxide fuel cells

The optimal anode mass fraction of La_0.9Sr_0.1Cr_0.5Mn_0.5O_3-δ (LSCM) and Gd_0.1Ce_0.9O_2-δ (GDC) is evaluated in this study. The anodes with GDC share of 30–100 wt.% are investigated. Initial polarization resistance decreased as the GDC share increased. However, anodes with GDC share over 80 wt.% significantly deteriorated in the degradation tests. Nano-scale cracks were observed in the GDC phase at the grain boundaries after the test. These nano-cracks were not observed in composite anodes, from which it is implied that LSCM has stabilization effect on GDC structure. The mass fraction of LSCM : GDC = 30 : 70 wt.% is found to be optimal in terms of initial electrochemical performance and stability. The optimal LSCM-GDC shows lower polarization resistance than conventional Ni-YSZ at low temperatures, which is comparable to Ni-GDC anode.     

Synthesis,CO2-tolerance and rate-determining step of Nb-doped Ce0.8Gd0.2O2−δ–Pr0.6Sr0.4Co0.5Fe0.5O3−δ ceramic membranes

In this work, CO₂-tolerant Ce_0.8Gd_0.2O_2δ–Pr_0.6Sr_0.4Co_0.5Fe_0.5−xNb_xO_3−δ (CG–PSCF_0.5−xN_x; x=0–0.125) dual-phase dense oxygen permeation membranes were successfully developed. The crystal structure, microstructure, oxygen permeability, rate-determining step and CO₂ tolerance were systematically investigated. The experimental results showed that the increase in CG content improved oxygen permeability and CO₂ tolerance. Thermogravimetry–differential-scanning-calorimetry analysis, X-ray photoelectron spectra and oxygen permeation tests indicated that the increase in Nb content caused a slight decrease in oxygen permeability, while the long-term CO₂ resistance can be improved significantly. According to the adopted permeation model, the weight ratio and thickness affect the oxygen permeability and permeation resistance distribution. By examining the distribution of three permeation resistances, we identified the rate-determining step and then optimized the weight ratio of the two phases, as well exploring the effects of thickness on oxygen permeability. All these experiments confirm that CG–PSCF_0.5−xN_x dual-phase membranes have great CO₂ tolerance and potential application in oxy-fuel combustion.     

Effect of microstructure on oxygen permeation of Ba0.5Sr0.5Co0.8Fe0.2O3−δ and SrCo0.8Fe0.2O3−δ membranes

The effect of grain size on oxygen permeation properties of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3?δ (BSCF) and SrCo_0.8Fe_0.2O_3?δ (SCF) membranes was investigated by variation of the dwell time. The membrane microstructure was examined by field-emission scanning microscopy (FE-SEM) and then evaluated using a statistical approach. With longer dwell times the grain growth was stimulated and leaded to grains with a narrower size distribution. The grains of SCF (average size from 11.3 to 19.9 μm) were found to be smaller than those of BSCF (average size from 13.9 to 41.3 μm). The oxygen permeation flux of BSCF membranes was found to be independent of grain size in the range from 24 to 42 μm. However, membranes with smaller grains (13.9 μm) show a decreased oxygen permeation flux. For the SCF membranes a decrease in permeation flux with larger grains was observed for average grain sizes between 11.3 and 19.9 μm. By transmission electron microscopy (TEM) formation of an oxygen ordered SrCo_0.8Fe_0.2O_2.5 brownmillerite by-phase could be observed at the oxygen-depleted sweep side of the membrane.     

Creep behavior of porous La0.6Sr0.4Co0.2Fe0.8O3-δ substrate material for oxygen separation application

Advanced oxygen transport membrane designs consist of a thin functional layer supported by a porous substrate material that carries mechanical loads. Creep deformation behavior is to be assessed to warrant a long-term reliable operation at elevated temperatures. Aiming towards an asymmetric composite, the current study reports and compares the creep behavior of La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) perovskite porous substrate material with different porosity and pore structures in air for a temperature range of 800–1000?°C. A porosity and pore structure independent average stress exponent and activation energy are derived from the deformation data, both being representative for the LSCF material. To investigate the structural stability of the dense layer in an asymmetric membrane, sandwich samples of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF) and La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) with porous substrate and dense layers on both side were tested by three-point bending with respect to creep rupture behavior of the dense layer. Creep rupture cracks were observed in the tensile surface of BSCF, but not in the case of LSCF.     

Electrochemical performance of Ni1−xFex–Ce0.8Gd0.2O1.9 cermet anodes for solid oxide fuel cells using hydrocarbon fuel

Ni_1?xFe_x bimetallic-based cermet anodes were investigated for hydrocarbon-fueled solid oxide fuel cells. Ni_1?xFe_x–Ce_0.8Gd_0.2O_1.9 cermet anodes were synthesized using a glycine nitrate process, and their electrical conductivity and the amount of carbon deposits were found to decrease with increasing Fe content. The anode polarization resistance for the CH₄ fuel was significantly reduced by Fe alloying, which was strongly related to the carbon deposition behavior. The maximum power density of the single cell with Ni_0.85Fe_0.15–Ce_0.8Gd_0.2O_1.9 in CH₄ at 800 °C was 0.27 W/cm². Fe alloying significantly improved the electrochemical performance of solid oxide fuel cells in CH₄ fuel by suppressing carbon deposition.