Cathode For Intermediate-temperature Solid Oxide Fuel Cells Research Articles

Effect of Mg-doping on electrochemical performance of PrBaFe2O5+δ cathode materials for solid oxide fuel cells

PrBaFe2O5+δ (PBF) is one of the promising cathode materials for intermediate-temperature solid oxide fuel cell (IT-SOFC) technology. However, as the operating temperature decreases, the electrochemical performance of this material deteriorates rapidly. To counter this, various doping strategies have been tested and reported in order to improve the electrochemical properties of this material at intermediate-temperatures. In this study, Mg-doping to partially substitute Fe of PBF was investigated. PrBaFe2–xMgxO5+δ (PBFMgx, x=0.1, 0.15, 0.2, 0.3) materials were successfully synthesized, and their electrochemical performance as IT-SOFC cathode was evaluated. It is shown that Mg-doping enhances the conductivity of PBF between 650–800 °C, impacts little on the area-specific resistance of oxygen reduction reaction at and above 700 °C, and, most significantly, improves the power density of the Ni-SDC/SDC/PBFMg0.15 single cell by 52% compared to the un-doped PBF. This enhanced electrochemical performance is attributed to the improvement in PBF conductivity by Mg-doping.

Improved electrochemical performance of high-entropy La0.8Sr0.2FeO3-based IT-SOFC cathode

It is widely accepted that solid oxide fuel cells (SOFCs) have the potential to be the most efficient and cost-effective system for the direct conversion of various fuels into electricity with low environmental pollution and high efficiency. Herein, we demonstrate a novel Fe-based high-entropy perovskite oxide as a cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The high-entropy perovskite La0.2Pr0.2Sm0.2Nd0.2Sr0.2FeO3-δ (HE-LSF), composed of La, Pr, Nd, Sm, and Sr is prepared by incorporating five components into the A-site of La0.8Sr0.2FeO3-δ (LSF). Doping of Pr, Nd, Sm, and Sr into the A-site significantly enhances the redox stability of LSF and restrains the surface Sr-segregation in both oxidizing and reducing conditions. The electrode polarization resistance of the anode-supported single cell with HE-LSF cathode is significantly low at intermediate temperature. Meanwhile, at 800 °C, the power density is 1029.2 mW/cm2, and the polarization resistance (Rp) is 0.101 Ω cm2, while at 700 °C, the power density is 581.52 mW/cm2 with an Rp of 0.21 Ω cm2 in humidified H2. Further, the HE-LSF cathode presents good and long-term stability at a constant voltage of 0.7 V for 100 h at 700 °C. The excellent electrochemical performance and stability results exhibit that Fe-based high-entropy perovskite oxide is a new promising candidate and cathode material for SOFCs at intermediate temperatures.

Turning bad into good: A medium-entropy double perovskite oxide with beneficial surface reconstruction for active and robust cathode of solid oxide fuel cells

The cathodes of solid oxide fuel cells (SOFCs) often suffer from detrimental cation segregations and associated impurities poisoning, leading to insufficient electroactivity and poor stability. Here we developed a medium-entropy double perovskite GdBa(Co1.2Mn0.2Fe0.2Ni0.2Cu0.2)O5-δ (ME-GBCO) for promising SOFC cathode. The increased configuration entropy can effectively tailor the surface composition with in situ formed active BaCoO3-δ (BCO) species, rather than inert and deleterious BaOx segregation on parent GdBaCo2O5-δ (GBCO) surface. Accordingly, the layered ME-GBCO cathode with beneficial surface reconstruction exhibited not only high oxygen reduction activity but excellent durability against CO2 impurity, enabling it a very attractive cathode for intermediate temperature SOFCs (IT-SOFCs). Our study provides a new idea for development of efficient and durable cathodes via configurational entropy induced rational surface reconstruction.

CO2/Cr-tolerance and oxygen reduction reaction of novel high-entropy perovskite cathode for intermediate temperature solid oxide fuel cell

The development and exploration of cathode oxides with outstanding electrocatalytic activity are critical processes aimed at achieving a decrease in the operation temperature of solid oxide fuel cells (SOFC). Herein, a novel high-entropy oxide, La0.2Pr0.2Nd0.2Sm0.2Gd0.2BaCoFeO5+δ (HEP), which incorporates five lanthanide species (La, Pr, Nd, Sm, and Gd) in the A-site of perovskite, has been specifically developed and assessed as selected cathode for intermediate-temperature SOFC. Investigations of phase structure, chemical compatibility, oxygen transport characteristics, oxygen reaction kinetic, thermal expansion, surface chemical state, conductivity, as well as CO2/Cr-durability are thoroughly performed to assess the basic physicochemical properties of the HEP cathodes. The HEP cathode possesses good operational stability, moderate thermal expansion behavior, fast oxygen transport dynamics, and superior chemical compatibility with the electrolyte. At 700 °C, the polarization resistance low to 0.072 Ω cm2 and output power density high to 332.2 mW cm−2 were obtained for the symmetrical and electrolyte-supported single cells. Furthermore, a stable current density is obtained for the single cell operating at 600 °C and 0.5 V for 100 h. Analysis of electrochemical impedance spectra (EIS) and distribution of relaxation time (DRT) data at different oxygen partial pressures reveal that the charge-transfer and oxygen ions ionization processes at intermediate frequencies present a significant limiting step in the rate of the oxygen reduction reaction. However, under realistic utilization conditions, cathodes of cells often endure irreversible performance degradation owing to the Cr deposition from interconnects or CO2 poisoning in air. Hence, the behavior of Cr and CO2 poisoning is also systematically investigated in symmetrical cell measurements; the results confirm that the HEP cathode displays good resistance to Cr and CO2 poisoning. Overall, our findings indicate that the HEP material is regarded as a favored ceramic cathode for SOFC.

Study of structural, electrical, and electrochemical properties of Sr3-xPrxFe1.8Co0.2O7-δ cathode for IT-SOFCs

Developing new cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs) is still challenging. In this study, co-doped Sr3Fe2O7-δ Ruddlesden-Popper (R-P) (Sr3-xPrxFe1.8Co0.2O7-δ x = (0–0.3)) cathode is synthesized by the polymer complex technique as a cathode for IT-SOFCs. The synthesized powders show a desired tetragonal structure of Sr3-xPrxFe1.8Co0.2O7-δ with an I4/mmm space group. The effect of Pr and Co on the physical, thermal, electrical, and electrochemical properties of the cathodes is investigated. The results reveal that Pr/Co co-doping improves electrochemical properties while increasing the electrical resistivity and average thermal expansion coefficients (TECs). To evaluate the long-term thermal stability of the cathode, they are heated at 800 °C for 100 h in the air, and no contaminant is found. In the optimal amount of Pr and Co (Sr2.7Pr0.3Fe1.8Co0.2O7-δ), area-specific resistance (ASR) of 0.058 Ω.cm2 and maximum output power density of 745 mW/cm2 are obtained at 800 °C. Strong oxygen-reducing reaction (ORR) activity and long-term thermal stability make Sr2.7Pr0.3Fe1.8Co0.2O7-δ an appropriate alternative cathode material for IT-SOFC.

Study on the composite structure of cobalt-free oxides as cathodes for intermediate temperature solid oxide fuel cells (IT-SOFCs)

Summary: Solid Oxide Fuel Cells (SOFCs) represent a promising technology for efficient and clean energy conversion. This study focuses on the design and development of a novel cathode material for SOFCs, specifically exploring the use of a free-cobalt cathode within a composite structure. Investigating the structure of cobalt-free composites of Ba0.5Sr0.5FeO3-δ (BSF) and Ba0.5Sr0.5Fe0.8B0.2O3-δ (B=Cu, Zn) (BSFB) have been prepared and evaluated as cathodes for IT-SOFCs. The solid-state reaction was employed for generating and modifying the composite structure of the model system. The decomposition reaction and the formation of perovskite structure have been observed using thermal gravimetric analysis and X-ray diffraction. The study encompasses experimental procedures, data processing using GSAS software, and the application of the Rietveld method to achieve precise analysis results. Rietveld analysis outcomes offer intricate details about the crystal structure, encompassing crystal unit parameters, and scale factors. The solid-state reaction led to the reduction in the weight of the composite during the heating process. The decomposition reaction of oxides was generated between 650 to 950 oC. The average of total weight loss during the period treatment was achieved up to 18 % and the perovskite phase formed in the composite structure. A single-phase perovskite from a cubic structure with space group Pm-3m was demonstrated by all composite’s models. The lattice parameter and a unit cell volume were obtained from the model system of BSF, BSFC and BSFZ, respectively. This study explores the potential development of SOFCs technology with the hope of making a positive contribution to advancing clean and sustainable energy solutions in the future

Characterization of B‐Site Sc‐doped La2Ni1-xScxO4+δ (x=0, 0.05, 0.10, and 0.15) perovskites as cathode materials for IT-SOFCs

Cathode materials play a crucial role in enabling the widespread adoption of intermediate-temperature solid oxide fuel cells (IT-SOFC) for commercial applications. This study utilized the sol-gel method to prepare a range of perovskite oxides, specifically Sc-doped La2Ni1-xScxO4+δ (x = 0, 0.05, 0.10, and 0.15), without the use of cobalt. The investigation focused on making a study of how the introduction of Sc doping affected the thermal stability, electrochemical properties, and structure of cathode materials. XRD, FE-SEM, and electrochemical workstations were subjected to structural characterization and performance testing of materials. The findings indicate that all the prepared materials have a typical Ruddlesden-Popper structure, and an abundance of additional oxygen can be generated in close proximity to the interstitial by incorporating Sc into the cathode of La2Ni1-xScxO4+δ to increase the oxygen vacancy and improve the catalytic activity of ORR. La2Ni0.9Sc0.1O4+δ has the highest oxygen surface exchange kinetics, the dissociative adsorption of oxygen is the rate-limiting step at the cathode. At a temperature of 700 °C, the lowest polarization resistance of La2Ni0.9Sc0.1O4+δ is 0.1298 Ω cm2, while the single cell with La2Ni0.9Sc0.1O4+δ as the cathode achieves an impressive peak power density of 0.462 W cm−2, thus demonstrating exceptional long-term stability. La2Ni0.9Sc0.1O4+δ is expected to be a potential high-performance IT-SOFC cathode material.

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.

A defective iron-based perovskite cathode for high-performance IT-SOFCs: Tailoring the oxygen vacancies using Nb/Ta co-doping

The sluggish kinetics of the electrochemical oxygen reduction reaction (ORR) in intermediate-temperature solid oxide fuel cells (IT-SOFCs) greatly limits the overall cell performance. In this study, an efficient and durable cathode material for IT-SOFCs is designed based on density functional theory (DFT) calculations by co-doping with Nb and Ta the B-site of the SrFeO3−δ perovskite oxide. The DFT calculations suggest that Nb/Ta co-doping can regulate the energy band of the parent SrFeO3−δ and help electron transfer. In symmetrical cells, such cathode with a SrFe0.8Nb0.1Ta0.1O3−δ (SFNT) detailed formula achieves a low cathode polarization resistance of 0.147 Ω cm2 at 650 °C. Electron spin resonance (ESR) and X-ray photoelectron spectroscopy (XPS) analysis confirm that the co-doping of Nb/Ta in SrFeO3−δ B-site increases the balanced concentration of oxygen vacancies, enhancing the electrochemical performance when compared to 20 mol% Nb single-doped perovskite oxide. The cathode button cell with Ni-SDC|SDC|SFNT configuration achieves an outstanding peak power density of 1.3 W cm−2 at 650 °C. Moreover, the button cell shows durability for 110 h under 0.65 V at 600 °C using wet H2 as fuel.

Enhancing the oxygen reduction reaction activity of SOFC cathode via construct a cubic fluorite/perovskite heterostructure

Pr2NiO4+δ-based (Ruddlesden-Popper) perovskite-structured oxide materials are promising candidates for low and intermediate temperature solid oxide fuel cells (SOFCs) systems. In this study, we prepared a high-performance cubic-fluorite/perovskite heterostructure Pr6O11-Pr1.2Sr0.8NiO4+δ (PO-PSNO) cathode for intermediate temperature SOFCs by solution impregnation method. By changing the impregnation amount of Pr6O11, the micro-morphology of the heterostructure was regulated, so that the heterostructure interface had the best reactive site. The oxygen reduction reaction (ORR) performance of Pr1.2Sr0.8NiO4+δ is improved, and the content of surface Sr in the heterostructure electrode material is reduced. Our results indicate that the synergistic effect of PO particles and PSNO skeleton makes the heterostructure exhibit a high oxygen surface exchange properties and catalytic performance. When the impregnation amount of PO particles reaches about 10% of the PSNO skeleton, the heterostructure has the best ORR activity. The oxygen surface exchange coefficient (Kchem) of 2-PO-PSNO is 5.8 × 10-4 cm·s−1, being 1.45 times as that of PSNO at 750 °C. Meanwhile, the polarization impedance (Rp) of 2-PO-PSNO is reduced by 66% to only 0.114 Ω cm2. Our study provides a new approach for developing high-performance RP structured perovskite cathodes and demonstrates practical applications in the field of SOFCs.

Perovskite SrCo0.5Fe0.25Cu0.2Nb0.05O3-δ cathode for intermediate-temperature solid oxide fuel cells: Improved working stability and CO2 tolerance

Commercial solid oxide fuel cells (SOFCs) primarily operate in the intermediate temperature range (600 °C–800 °C); hence, developing cathode materials with good stability and excellent catalytic activity in this temperature range is necessary. Herein, we are reporting the performance of SrCo0.5Fe0.5O3−δ (SCF) and SrCo0.5Fe0.25Cu0.2Nb0.05O3−δ (SCFCN) perovskite oxide as cathode materials for solid oxide fuel cells (SOFCs). The SCFCN sample maintains a cubic structure under a CO2 atmosphere. The polarization resistance of the SCFCN cathode on La0.9Sr0.1Ga0.83Mg0.17O3−δ (LSGM) reaches 0.067 Ωcm2 at 700 °C. The charge transfer and oxygen reduction reactions of the SCFCN cathode on the LSGM electrolyte are the main rate-limiting steps at 600 °C–700 °C. The SCFCN cathode maintains good electrochemical stability during a 200-h test with a configuration of SCFCN/LSGM/SCFCN symmetrical cell. Compared with SCF, the doping of Cu and Nb effectively reduces the Rp attenuation of SCFCN from 0.00012 to 0.00005 Ωcm2/h. The output power density of the fuel cell with SCFCN as the cathode on LSGM reaches 1124 mWcm−2 at 800 °C. This indicates that SCFCN can be a potential material for fabricating cathode for intermediate-temperature SOFCs (IT-SOFCs).

In situ XRD and TGA/DTA study of multiphase La- and Nd-substituted Pr2NiO4 under IT-SOFC cathode operating conditions

Promising cathode materials Pr2−x(La/Nd)xNiO4+δ (x = 0, 0.5, 1) for intermediate temperature solid oxide fuel cells (IT-SOFC) were synthesised via a Pechini route. The samples were studied by in situ XRD in the conditions close to operating for IT-SOFC cathode. For all the samples a phase inhomogeneity was determined, manifesting itself in the apparent presence of two phases with the same 1st order Ruddlesden-Popper structure. The two phases had different unit cell parameters and slightly different phase transition (sp.gr. Fmmm ↔ I4/mmm) temperatures. For the as-synthesised PrNdNiO4+δ sample a loss of crystallinity, accompanied by a release of H2, H2O, CO2 and CO gases upon heating in an inert atmosphere, was observed. The crystallinity of the sample was recovered upon subsequent heating in an air atmosphere. La- and Nd- doping increased thermal stability of samples compared to the undoped one in air at 700 °C. In situ XRD experiments were supplemented by TGA/DTA measurements performed in the same conditions.

Bi0.5Sr0.5FeO3-δ perovskite B-site doped Ln (Nd, Sm) as cathode for high performance Co-free intermediate temperature solid oxide fuel cell

The commercialization of the Co-free solid oxide fuel cell (SOFC) cathode was hindered due to its insufficient oxygen reduction reaction (ORR) activity. In this paper, the ORR activity of the cathode material is effectively increased by doping a small amount of low-valence Ln3+ (Nd3+, Sm3+) ions at the B-site of Fe-based perovskite Bi0.5Sr0.5FeO3-δ (BSF). Nd3+ increases the free volume (Vfree) per unit cell of perovskite due to its larger ionic radius, thus increasing the oxygen vacancy concentration of Bi0.5Sr0.5Fe0.95Nd0.05O3-δ (BSFN). Compared with BSF, BSFN has greatly improved the surface oxygen exchange and volume diffusion rate through the electronic conductivity relaxation (ECR) method. At 700 °C, the area-specific resistance (ASR) of BSFN reached 0.062 Ω cm2, which was 65% lower than that of BSF (0.177 Ω cm2), and the peak power density (PDD) of BSFN-based single cell reached 1.10 W cm−2, which was 1.7 times higher than that of BSF-based single cell (0.64 W cm−2). Through DRT analysis, it is concluded that BSFN can accelerate the adsorption/dissociation process of oxygen due to its higher oxygen vacancy concentration compared with BSF, so that ORR is not limited to the three-phase interface but extends to the entire cathode surface. In addition, in the 80 h long-term stability test at 600 °C, the BSFN-based single cell has better long-term stability because the thermal expansion coefficient of BSFN (14.1 × 10−6 K−1) is lower than that of BSF (14.4 × 10−6 K−1). In general, BSFN is expected to become a Co-free base high-performance intermediate temperature SOFC cathode.

A Ruddlesden–Popper oxide as a carbon dioxide tolerant cathode for solid oxide fuel cells that operate at intermediate temperatures

Solid oxide fuel cells (SOFCs) that operate at intermediate temperatures of 600 to 800 °C have recently received increased attention due to their improved durability, more rapid startup and shutdown, better sealing and lower cost than their counterparts operate at high temperatures. Nevertheless, intermediate-temperature SOFCs (IT-SOFCs) with popular perovskite cathodes contain alkaline-earth elements, which are prone to reaction with carbon dioxide (CO2), even when the CO2 content is comparatively low. In this work, an alkaline-earth metal-free Ruddlesden–Popper oxide, Nd1.8La0.2Ni0.74Cu0.21Ga0.05O4+δ (NLNCG), is developed for IT-SOFC cathodes. The cell is based on an electrolyte with 8 mol% Y2O3-stabilized ZrO2 (8YSZ). The NLNCG cathode exhibits an excellent CO2 tolerance, as proven by thermogravimetry analysis (TGA), in situ X-ray diffraction (XRD), I-V-P test, and electrochemical impedance spectroscopy (EIS), and stability measurements. The anode-supported single-cell NiO-YSZ|YSZ|NLNCG outputs a peak power density (PPD) of 0.522 W·cm-2 at 800 °C. These findings suggest that NLNCG could be a highly suitable cathode material with CO2 tolerance for IT-SOFCs.

A medium entropy cathode with enhanced chromium resistance for solid oxide fuel cells

Perovskite type SrCo0.9Ta0.1O3-δ (SCT91) cathode exhibits high activity for oxygen reduction reactions, but the instability in Cr-containing atmosphere restricts its application in intermediate temperature solid oxide fuel cells (IT-SOFCs). In this study, a B-site medium-entropy SrCo0.5Fe0.2Ti0.1Ta0.1Nb0.1O3-δ (SCFTTN52111) cathode is proposed and investigated as a potential Cr-tolerance cathode. The electrochemical activity of pristine SCT91 cathode degrades rapidly in the presence of volatile chromium species. In contrast, SCFTTN52111 performs very stable. Chromium vapors prefer to react with segregated SrO species rather than Co3O4 precipitates. Significant secondary phases of SrCrO4 and Co3O4 are detected on SCT91 electrode, while only trace by-products are found on medium-entropy cathode. The better Cr tolerance is closely related to the enhanced structural stability by medium-entropy engineering and reduced surface Sr segregations. This work sheds light on the development of robust cathodes for IT-SOFCs through rational design of configuration entropy.

Physiochemical and Electrochemical Properties of Lanthanum Strontium Cobalt Ferum–Copper (II) Oxide Prepared via Solid State Reaction

Lanthanum strontium cobalt ferum (LSCF) with addition of copper oxide (CuO) can serve as an alternate cathode material in Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC) due to its strong catalytic activity for oxygen reduction process at intermediate temperatures and great chemical compatibility. This study was done to determine the viability of LSCF–CuO composite as a material for the IT-SOFC cathode. The cathode powder was synthesised using the conventional solid-state process at intermediate temperatures range (600ºC–900ºC). The thermogravimetric analysis demonstrated that when LSCF was calcined at temperatures over 600ºC, the weight loss curve flattened. In the meantime, x-ray diffraction revealed that the perovskite structure of LSCF-CuO was completely formed after calcined at 800ºC. Moreover, the Brunauer– Emmett–Teller (BET) and scanning electron microscope investigations demonstrated that as the calcination temperature rose, the LSCF–CuO particles tended to grow. The electrochemical impedance spectroscopy investigation revealed polarisation resistance of samples calcined at 800ºC (0.41 Ωcm2) was significantly lower than that of samples calcined at 600ºC (29.57 Ωcm2). Judging from chemical, physical and electrochemical properties, it is evidence that LSCF-CuO prepared via simple solid-state reaction has a potential to be used as cathode material for IT-SOFC.

A/B-site co-doping enabled fast oxygen reduction reaction and promoted CO2 tolerance of perovskite cathode for solid oxide fuel cells

The significant challenges facing the development of the cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs) are the poor oxygen reduction reaction (ORR) activity as well as the CO2 poisoning issues. Herein, an La/Nb co-doped perovskite Ba0.9La0.1Co0.7Fe0.2Nb0.1O3-δ (BLCFN) has been developed as a promising cathode for IT-SOFCs. The polarization resistance of BLCFN cathode is 0.073 Ω cm2 at 700 °C air. This remarkable improved ORR activity can be attributed to the increased oxygen vacancies caused by the introduction of La3+ and Nb5+ ions. Furthermore, the collaboration introduction of La3+ and Nb5+ ions greatly reduce the alkalinity of the BLCFN electrode, bringing excellent CO2-tolerance for BLCFN cathode. No carbonate is yielded on the surface of the BLCFN cathode. The improvement on CO2-tolerance for these cathodes is largely attributed to the introduction of Nb5+ ions, which have higher acidity and more powerful M − O bond, and the introduction of La3+ can improve the ORR activity of the material on this basis. The co-doping of La/Nb elements furtherly stabilizes the lattice structure. Overall, the high ORR activity and CO2-tolerance of the cathode manifest a bright application prospect for BLCFN cathode in SOFCs and other membrane reactors.

Facile Approach to Enhance Activity and CO2 Resistance of a Novel Cobalt-Free Perovskite Cathode for Solid Oxide Fuel Cells.

Developing high-performance and cost-effective cathodes is ever-increasingly vital for the advancement of intermediate-temperature solid oxide fuel cells (IT-SOFCs). To facilitate the popularization of nonprecious metallic and cobalt-free oxygen reduction electrodes, herein, we propose a novel perovskite-based BaFeO3-δ (BF) matrix, Ba0.75Sr0.25Fe0.875Y0.125O3-δ (BSFY), as a highly active cathode for IT-SOFCs. To our satisfaction, the BSFY electrode showcases a low area-specific resistance of 0.063 Ω cm2, as well as a high peak power density of 1288 mW cm-2 at 600 °C, yielding a more than threefold improvement compared to that of its BF counterpart (371 mW cm-2). The long-term durability test highlights its practicability under the IT operating condition. When tested in 10 vol % CO2-containing air, the BSFY electrode exhibits impressive resistance against contaminants within 50 h (<0.4 Ω cm2 with a deterioration rate of ∼0.00011 Ω cm2 min-1). Coupled with its reversible response between pure air and the contaminant, the BSFY cathode is expected to be a promising cobalt-free alternative with high CO2 resistance for IT-SOFCs.

Triple Perovskite Nd1.5Ba1.5CoFeMnO9-δ-Sm0.2Ce0.8O1.9 Composite as Cathodes for the Intermediate Temperature Solid Oxide Fuel Cells.

Triple perovskite has been recently developed for the intermediate temperature solid oxide fuel cell (IT-SOFC). The performance of Nd1.5Ba1.5CoFeMnO9−δ (NBCFM) cathodes for IT-SOFC is investigated in this work. The interfacial polarization resistance (RP) of NBCFM is 1.1273 Ω cm2~0.1587 Ω cm2 in the range of 700–800 °C, showing good electrochemical performance. The linear thermal expansion coefficient of NBCFM is 17.40 × 10−6 K−1 at 40–800 °C, which is significantly higher than that of the electrolyte. In order to further improve the electrochemical performance and reduce the thermal expansion coefficient (TEC) of NBCFM, Ce0.8Sm0.2O2−δ (SDC) is mixed with NBCFM to prepare an NBCFM-xSDC composite cathode (x = 0, 10, 20, 30, 40 wt.%). The thermal expansion coefficient decreases monotonically from 17.40 × 10−6 K−1 to 15.25 × 10−6 K−1. The surface oxygen exchange coefficient of NBCFM-xSDC at a given temperature increases from 10−4 to 10−3 cm s−1 over the range from 0.01 to 0.09 atm, exhibiting fast surface exchange kinetics. The area specific resistance (ASR) of NBCFM-30%SDC is 0.06575 Ω cm2 at 800 °C, which is only 41% of the ASR value of NBCFM (0.15872 Ω cm2). The outstanding performance indicates the feasibility of NBCFM-30% SDC as an IT-SOFC cathode material. This study provides a promising strategy for designing high-performance composite cathodes for SOFCs based on triple perovskite structures.

Impacts of A-site gadolinium doping on electrocatalytic performance of La0.33Ba0.62Gd0.05Co0.7Fe0.3O3-δ to realize promising cathode for intermediate-temperature solid oxide fuel cells

With respect to intermediate-temperature solid oxide fuel cells (IT-SOFCs), electrocatalytic activity of the cathodes dominates their output power. Herein A-site gadolinium-doped La0.33Ba0.62Gd0.05Co0.7Fe0.3O3-δ (LBG0.05CF) perovskite is synthesized and systematically evaluated as the cathode for IT-SOFCs. We demonstrate outstanding catalytic activity of LBG0.05CF toward oxygen reduction reaction (ORR). Benefiting from enhanced electrical conductivity, oxygen surface exchange and diffusion rates, the ORR activity of LBG0.05CF outperforms that of La0.33Ba0.67Co0.7Fe0.3O3-δ (LBCF), as evidenced by the lower polarization resistance (0.035 Ω cm2) at 700 °C. The Ce0.9Gd0.1O1.95 (CGO) electrolyte-supported fuel cell with the LBG0.05CF cathode delivers a peak power density (PPD) of 371 mW cm−2 at 700 °C, which surpasses the PPD (278 mW cm−2) for LBCF-based cell. Furthermore, LBG0.05CF exhibits an improved CO2 tolerance compared with pristine LBCF. These results highlight a promising strategy of A-site replacement of Ba by lanthanide for optimizing catalytic ORR activity of the perovskite materials.