Cathode Material For Solid Oxide Fuel Cells Research Articles

Atomic-scale mechanistic study of oxygen reduction mechanism for B-site doped Pr(Ba,Sr)Co2O5+δ by density functional theory calculations

Pr(Ba,Sr)Co2O5+δ is a promising cathode material for solid oxide fuel cell (SOFC) due to its high oxygen ion transport capability and oxygen reduction activity. Density functional theory (DFT) calculations were performed to elucidate the oxygen reduction mechanism of B-site doped Pr(Ba,Sr)(Co,M)2O5+δ (M = Fe, Ni, Cu, and Zn) materials. First, we investigated the formation of O vacancies. The results indicate that Cu and Zn doping facilitate O vacancy formation, resulting in lower O vacancy formation energies. Furthermore, the interaction between oxygen and the (0 0 1) surfaces of B-site doped Pr(Ba,Sr)(Co,M)2O5+δ has been comprehensively discussed, involving both perfect and defective surfaces. The results demonstrate that the presence of O vacancies enhances the catalytic activity for oxygen reduction, by reducing the energy required for O2 dissociation. Zn-doped Pr(Ba,Sr)(Co,M)2O5+δ exhibits a low O vacancy formation energy, resulting in a stable adsorption configuration upon oxygen dissociation, indicating its potential as a cathode material for SOFC.

Application of the electrospinning technique in the preparation of selected electrode materials for solid oxide fuel cells

Abstract The electrospinning technique was applied to prepare cathode materials for solid oxide fuel cells (SOFCs). The research aimed to determine the influence of the Poly(vinylpyrrolidone) (PVP) content in the solution of a Sm0.5Ba0.25Sr0.25Co0.5Cu0.5O3-d perovskite oxide on the properties of the spun material, and consequently, on the performance of the fuel cell. The chosen material, commonly used as a cathode material for SOFCs, has been altered by the replacement of toxic barium and cobalt with less harmful strontium in the A-site and copper in the B-site. A single-phase perovskite structure was obtained after annealing at 900°C for two hours. The research included a process of preparing the precursor solution and obtaining samples by the electrospinning technique, followed by a series of studies to determine the morphology and phase composition, electrode and cell fabrication, and characterization of their electrochemical properties. The results indicated that material derived from a precursor with the addition of 15 wt.% PVP had the lowest polarization resistance values (e.g. 0,865 Ω cm−2 at 800 °C) between 600°C - 900°C temperature range. This material was then screen-printed on a commercial anode-supported fuel cell as a cathode layer, which allowed to achieve a promising power density value close to 300 mW cm−2 at 800 °C.

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.

Advancing Solid Oxide Fuel Cell Performance: Enhanced Electrochemical Properties of Pr1-xCaxBaFe2O5+δ Nanofiber Cathodes via Ca Doping.

The double perovskite oxide PrBaFe2O5+δ has great potential as a cathode material for solid oxide fuel cells (SOFCs). However, the electrochemical characteristics of Fe-based double perovskites are relatively inferior. To improve its electrochemical performance, Ca is investigated to partially replace Pr, forming Pr1-xCaxBaFe2O5+δ (PCBFx, x = 0.0-0.3) by an electrospinning technique. The PCBFx nanofibers exhibited a crystalline structure characterized by orthorhombic symmetry and space group P4/mmm. Furthermore, these PCBFx nanofibers displayed exceptional chemical compatibility with the Sm0.2Ce0.8O1.95 (SDC) electrolyte when sintered at a temperature of 900 °C for 5 h. The X-ray photoelectron spectroscopy (XPS) analysis reveals a progressive increase in the Fe4+ concentration as the Ca doping level rises. The polarization resistances (Rp) of the PCBF00, PCBF01, PCBF02, and PCBF03 nanofiber cathodes were 0.103, 0.079, 0.056, and 0.048 Ω cm2 at 750 °C. In the meantime, doping Ca increases the peak power density of the single cell by 46%, from 762.80 (PCBF00) to 1114.85 (PCBF03) mW cm-2 at 750 °C. The results demonstrate that PCBF03 double perovskite nanofibers exhibit great potential as cathode materials for SOFCs.

Preparation and characterization of Pr1-xNdxBaFe2O5+δ nanofiber cathodes for solid oxide fuel cells

Double perovskite oxide Pr1-xNdxBaFe2O5+δ (PNBFx, x = 0.0–0.3) nanofiber were prepared using electrospinning and were evaluated as cathodes for solid oxide fuel cells (SOFCs). The crystalline structure, microstructure, and electrochemical performance of PNBFx were thoroughly investigated and discussed. The PNBFx nanofiber cathodes obtained after sintering at 800 °C crystallized in a tetragonal structure with the space group P4/mmm and had good chemical compatibility with SDC electrolytes at 900 °C for 4 h. Nd doping was found to increase the lattice parameter, while the average valence of praseodymium and iron content increased steadily in PNBFx. The Pr0.8Nd0.2BaFe2O5+δ (PNBF02) nanofiber cathode exhibited the best performance with a polarization resistance (Rp) of 0.072 Ω cm2 at 750 °C. When PNBF02 nanofiber was used as a single-cell cathode, the peak power density reached 1.52 W cm2 at 750 °C. All results indicate that double perovskite PNBF02 is a promising cathode material for SOFCs.

First principles calculation and experimental study of Ln0.125Sr0.875Co0.875Ta0.125O3-δ(Ln = La, Sm, and Nd) as potential cathode materials for intermediate-temperature solid oxide fuel cells

Solid oxide fuel cells (SOFCs), as important energy equipment, have excellent characteristics, including low pollution and high catalytic activity. The cathode, which is the key component of an SOFC, plays a vital role in practical applications. Herein, we study the properties of Ln0.125Sr0.875Co0.875Ta0.125O3-δ (Ln = La, Sm, and Nd, abbreviated as LSCT, SSCT, and NSCT, respectively) cathode materials both theoretically and experimentally. The conductivity of LnSCT gradually decreased with decreasing Ln3+ ionic radius. Density of states (DOS) analysis indicated that LSCT has the highest conductivity owing to the band center of Co 3d being closer to O 1s. Density functional theory (DFT) calculations showed that the SSCT sample has the lowest oxygen vacancy formation energy, which facilitated the formation of oxygen vacancies. The binding energy results show that SSCT and NSCT have relatively good structural stability compared to LSCT. The polarization impedance values of LSCT, SSCT, and NSCT at 700 °C are 0.105, 0.069, and 0.304 Ω cm2, respectively. The CO2 sensitivity of LSCT, SSCT, and NSCT was evaluated by calculating the CO2 adsorption energy and performing impedance tests under different CO2 concentrations. These results indicate that LSCT and SSCT have better CO2 tolerance than NSCT. At 700 °C, for Ln = La, Sm, and Nd, the maximum power of NiCu-SDC/SDC/LSGM/LnSCT electrolyte-supported fuel cell reached 430, 462, and 382 mW cm−2, respectively. These findings provide a reference for the future design and development of SOFCs cathode material.

A medium-entropy engineered double perovskite oxide for efficient and CO2-tolerant cathode of solid oxide fuel cells

Developing highly active and robust cathodes remains challenging for solid oxide fuel cells (SOFCs). Therefore, we report an A-site medium-entropy double perovskite oxide PrBa0.5Sr0.25Ca0.2Ce0.05Co2O5+δ (PBSCCC) and its electrocatalytic activity and CO2 tolerance property are systematically probed. The PBSCCC cathode exhibits excellent oxygen reduction reaction (ORR) activity with a low polarization resistance of 0.027 Ω cm2 at 700 °C. More importantly, compared to PrBaCo2O5+δ (PBC) and PrBa0.8Ca0.2Co2O5+δ (PBCC) oxides, its CO2 resistance is prominently enhanced with significantly less BaCO3 and Co3O4 impurities formed. The superior ORR performance and structure stability are mainly attributed to its high electrical conductivity and significantly reduced surface cation segregations. Our results show that the potential of PBSCCC as a cathode material for SOFCs is enormous and also prove the rationality and feasibility of entropy engineering for cathode development.

Fabrication and performance investigation of high entropy perovskite (Sr0.2Ba0.2Bi0.2La0.2Pr0.2)FeO3 IT-SOFC cathode material

The high-entropy oxide (HEO) concept expands the design space of solid oxide fuel cell (SOFC) cathode materials. There is great potential for the development of HEO cathode materials that has not been fully explored, and the relationship between their chemical composition, grain size, and electrochemical performance is not yet fully understood. This experimental design involved the preparation of single-phase perovskite (Sr0.2Ba0.2Bi0.2La0.2Pr0.2)FeO3 HEO SOFC cathode materials, and we systematically studied the effects of synthesis temperature and microstructure on their electrochemical performance. The results show that as the synthesis temperature increases, structural transformations from multiphase to single-phase perovskite HEO can be observed. It exhibits excellent conductivity and electrochemical performance (the minimum polarization resistance reaches 0.033 Ω∙cm2, and the maximum power density is 664 mW∙cm−2). The single-phase perovskite HEO sample exhibits higher electrochemical performances compared to those of multiphase perovskite. Furthermore, it exhibits outstanding ability to suppress Sr segregation, chemical compatibility with Ce0.8Sm0.2O1.9(SDC), and CO2 tolerance performance. The Distribution of relaxation time(DRT) analysis shows that as the synthesis temperature (1000–1150 ℃) increase, HEO single-phase formed and the oxygen atom reduction ability of the SBBLP samples was improved; and the adsorption of gas oxygen on the electrode surface is limited with porosity decreases. The work shows it is interesting and valuable to optimize the performance of SOFC cathode materials using a high entropy design.

Ce-doping enhanced ORR kinetics and CO2 tolerance of Nd1-xCexBaCoFeO5+δ (x = 0–0.2) cathodes for solid oxide fuel cells

Addressing challenges in oxygen reduction efficiency and CO2 endurance is essential for advancing the electrochemical energy conversion performance of solid oxide fuel cells (SOFCs). This investigation introduces an innovative strategy by employing Ce doping to enhance the oxygen reduction kinetics and CO2 resistance of NdBaCoFeO5+δ (NBCF) cathodes. Ce doping effectively regulates the oxygen vacancy content, the ratio of Co3+/Co4+ and Fe3+/Fe4+ in NBCF, leading to substantial improvements in oxygen exchange, lattice diffusion, and charge transfer processes. Consequently, a significant enhancement in the oxygen reduction reaction catalytic activity and CO2 endurance is achieved. At 800 °C, the introduction of 10 mol% Ce doping results in a 65.3% reduction in Rp, reaching 0.024 Ω cm2. Simultaneously, the power density experiences a 50.8% enhancement, reaching 1.0 W cm−2. The current investigation presents a novel avenue towards the advancement of next-generation high-efficiency and stable cathode materials for SOFCs.

Ta/Nb doping motivating cubic phase stability and CO2 tolerance of Sr2Co1.6Fe0.4O6-δ double perovskite for high-performing SOFC cathode

Developing cathodes that are both phase-stable and tolerant to carbon dioxide (CO2) is a crucial and challenging task for solid-oxide fuel cells (SOFCs) operating at reduced temperatures. The activity of oxygen reduction reaction (ORR) in SOFC cathodes is typically influenced by factors such as geometric features and oxygen vacancies. In this study, new and robust cathodes for SOFCs, Sr2Co1.5Fe0.4Ta0.1O5+δ (SCFT) and Sr2Co1.5Fe0.4Nb0.1O5+δ (SCFN) are developed by doping a small amount of niobium (Nb) and tantalum (Ta) into Sr2Co1.6Fe0.4O5+δ (SCF) using a simple solid-state reaction technique. The effects of Nb/Ta doping on the crystal structure, oxygen vacancies, electrical conductivity, and electrochemical properties of SCFT and SCFN are investigated. The results reveal that these materials possess a fully cubic structure in the Fm-3m space group, with improved oxygen vacancy and electrical conductivity. They also exhibit good chemical compatibility with electrolytes at 1100 °C for 8 h and remain thermally stable when exposed to air and CO2 at 700 °C, without any additional phase formation. The area-specific resistance (ASR) of the SCFT cathode is found to be only 0.06 Ω cm2, whereas the SCFN cathode has an ASR of 0.10 Ω cm2. The superior performance of SCFT can be attributed to the higher oxygen vacancy, which enhances oxygen surface exchange kinetics and diffusivity compared to SCFN. When tested in a single cell using humidified H2 as the fuel and ambient air as the oxidant, the SCFT cathode achieves a power density of 656 mW cm−2 at 700 °C, while the SCFN cathode reaches 559 mW cm−2, indicating the potential of SCFT as a promising cathode material for SOFCs. The excellent performance of these materials can be attributed to their mixed electronic-ionic conduction properties, unique structural features, and high observed oxygen vacancy, which contribute to their remarkable electronic conductivity and significant ionic mobility.

Boosting the electrochemical performance of oxygen electrodes via the formation of LSCF-BaCe0.9–xMoxY0.1O3–δ triple conducting composite for solid oxide fuel cells: Part II

This research is the continuation of our previous work, in which we introduced novel proton-conducting electrolytes BaCe0.9–xMoxY0.1O3–δ (BCMxY; x = 0.025, 0.05). In this study, we explore the potential of the proton-conducting BCM0.025Y electrolyte by creating a composite with La0.6Sr0.4Co0.2Fe0.8O3–δ (LSCF) to form triple conducting electrodes for solid oxide fuel cells (SOFC). The formation of the LSCF-BCM0.025Y composite enhances both the three-phase reaction interface length and the concentration of oxygen vacancies, contributing to improved dissociation rates and enhanced oxygen adsorption. The desired characteristics, including density, structure, composition, electrochemical performance, and thermal stability, have been confirmed through a comprehensive set of analyses including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), electrochemical impedance spectroscopy (EIS), and thermogravimetric analysis (TGA) coupled with differential scanning calorimetry (DSC), respectively. The cell configuration of Ni-YSZ | BCZY | LSCF-BCM0.025Y exhibited a remarkable maximum power density (MPD) of 418.7 mW cm−2, which is approximately 29 % higher than that achieved with a typical LSCF cathode (325.6 mW cm−2) at an operating temperature of 600 °C. The outstanding performance and enduring stability of the LSCF-BCM0.025Y composite over a 500 h period demonstrate its potential as a promising cathode material for intermediate-temperature SOFCs.

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

High activity and stability of cobalt-free SmBa0.5Sr0.5Fe2O5+δ perovskite oxide as cathode material for solid oxide fuel cells

It is very important to develop cathode material with high stability and strong catalytic activity to realize the commercial application of solid oxide fuel cells (SOFCs). Here, we prepared a cobalt-free cathode material which partial substitution of Sr for Ba in SmBa0.5Sr0.5Fe2O5+δ (SBSF) sample and systematically investigated its electrochemical performance. Density functional theory (DFT) results showed that the oxygen vacancy formation energy of SBSF was lower than that of SmBaFe2O5+δ (SBF). The local density of state (LDOS) results showed that bandwidth center energy of SBSF between O-2p and Fe-3d obviously overlapped compared with parent SBF. The XRD spectra show that the SBSF formed a perovskite structure and had good chemical compatibility with La0.9Sr0.1Ga0.83Mg0.17O3-δ (LSGM) and CeO2-based electrolyte, respectively. At 800 °C, the polarization resistance and maximum power density of SBSF cathode on LSGM electrolyte were 0.023 Ω cm2 and 874 mWcm−2, respectively. In addition, the polarization resistance of SBSF electrode was stable during the 100 h test. The preliminary results show that SBSF oxide is a promising cathode material for SOFCs.

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, (La0.6Sr0.4)0.9Fe0.8Ni0.2O3-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.

Computational Screening of La2NiO4+δ Cathodes with Ni Site Doping for Solid Oxide Fuel Cells.

Doping on the crystal structure is a common strategy to modify electronic conductivity, ion conductivity, and thermal stability. In this work, a series of transition metal elements (Fe, Co, Cu, Ru, Rh, Pd, Os, Ir, and Pt) doped at the Ni site of La2NiO4+δ compounds as cathode materials of solid oxide fuel cells (SOFCs) are explored based on first-principles calculations, through which the determinant factors for interstitial oxygen formations and migrations are discussed at an atomistic level. The interstitial oxygen formation and migration energies for doped La2NiO4 are largely reduced in contrast to the pristine La2NiO4+δ, which is explained by charge density distributions, charge density gradients, and Bader charge differences. In addition, based on a negative correlation between formation energy and migration barrier, the promising cathode materials for SOFCs were screened out between the doped systems. The Fe-doped structures of x = 0.25, Ru-doped structures of x = 0.25 and x = 0.375, Rh-doped structures of x = 0.50, and Pd-doped structures of x = 0.375 and x = 0.50 are screened out with interstitial oxygen formation energy less than -3 eV and migration barrier less than 1.1 eV. In addition, DOS analysis indicates that doping to La2NiO4+δ also facilitates the electron conductions. Our work provides a theoretical guideline for the optimization and design of La2NiO4+δ-based cathode materials by doping.

Preparation of Pr2NiO4+δ-La0.6Sr0.4CoO3-δ as a high-performance cathode material for SOFC by an impregnation method

As a Ruddlesden-Popper (RP) phase solid oxide fuel cell (SOFC) cathode material, Pr2NiO4+δ (PNO) is a critical challenge for SOFC commercialization due to the lack of oxygen vacancies and insufficient redox reaction (ORR) activity. In this paper, various concentrations of La0.6Sr0.4CoO3-δ (LSC) nanoparticles are coated on the surface of PNO by an impregnation method, and the ORR kinetics of PNO is found to be improved by constructing a composite cathode with heterointerfaces. The formation of the heterointerface effectively enhances the transfer of interstitial oxygen in the PNO and the oxygen vacancies in LSC, which can promote the conduction of O2− in the cathode and thus improves the ORR activity of the material. When the impregnation concentration of LSC reached CLSC = 0.2 mol L−1, the ORR activity can reach the highest level. At 700 °C, the area-specific resistance of PNO-LSC reaches 0.024 Ω cm2, which is 83.4% lower than that of PNO (0.145 Ω cm2). And the peak power density of PNO-LSC reaches 0.618 W cm−2, which is 1.89 times larger than that of PNO (0.327 W cm−2). Therefore, the construction of composite cathodes with heterointerfaces via impregnation provides an alternative strategy for enhancing the ORR activity of the cathode materials in SOFC.

Nanomaterials with oxygen mobility for catalysts of biofuels transformation into syngas, SOFC and oxygen/hydrogen separation membranes: Design and performance

Modern hydrogen energy technologies include generation of syngas and pure hydrogen from biofuels to be used for green energy production in solid oxide fuel cells (SOFC). To be economically feasible, these processes require design of stable, efficient and inexpensive catalysts, permselective membranes for hydrogen and oxygen separation as well as SOFC cathode and anode materials. In all cases, such materials should possess a high oxygen mobility. This review presents results of our research devoted to design of materials based on complex oxides with fluorite, perovskite, and spinel structures used in these applications. The key aspect is characterization of their oxygen mobility by unique method of temperature –programmed oxygen heteroexchange in flow reactors and finding its dependence on their composition, real structure/microstructure and surface properties affected by methods of synthesis and elucidated with the help of modern structural, spectroscopic and kinetic methods. Optimized materials were shown to provide stable and efficient performance in catalytic reactors, membranes and solid oxide fuels cells.

Novel CO2-tolerant Co-based double perovskite cathode for intermediate temperature solid oxide fuel cells

For the commercial application of solid oxide fuel cells (SOFCs), CO2-tolerant cathode materials with high electrochemical activity are required. Here, we discuss the performance of double perovskite Pr0.2Sr1.8CoTiO6−δ (P02STC) as a potential cathode material for SOFCs. P02STC has a cubic structure and keeps lattice structure stable in the CO2 atmosphere. The average thermal expansion coefficient is 17.8 × 10–6 K–1 at 30–900 °C in air. The P02STC cathode exhibits good electrochemical performance with a low polarization resistance of 0.080 Ωcm2 at 700 °C. The P02STC cathode shows good structure stability, electrochemical performance stability, and excellent tolerance to CO2 poisoning for the symmetrical cells based on the 350 h stability test in air and the 150 h stability test in O2 containing 5%CO2 at 700 °C. The electrolyte-supported single cell with a P02STC cathode shows a maximum power density of 677 mW cm− 2 at 800 °C. The single cell operates stably for 250 h at a constant current of 0.3 A/cm2 without obvious degrading performance. According to all of the experimental results, the P02STC sample might be a promising candidate cathode for SOFCs.

Enhanced cathodic activity by tantalum inclusion at B-site of La0.6Sr0.4CO0.4Fe0.6O3 based on structural property tailored via camphor-assisted solid-state reaction

Lanthanum strontium cobalt ferrite (LSCF) is an appreciable cathode material for solid oxide fuel cells (SOFCs), and it has been widely investigated, owing to its excellent thermal and chemical stability. However, its poor oxygen reduction reaction (ORR) activity, particularly at a temperature of ⩽ 800 °C, causes setbacks in achieving a peak power density of > 1.0 W·cm−2, limiting its application in the commercialization of SOFCs. To improve the ORR of LSCF, doping strategies have been found useful. Herein, the porous tantalum-doped LSCF materials (La0.6Sr0.4Co0.4Fe0.57Ta0.03O3 (LSCFT-0), La0.6Sr0.4Co0.4Fe0.54Ta0.06O3, and La0.6Sr0.4Co0.4Fe0.5Ta0.1O3) are prepared via camphor-assisted solid-state reaction (CSSR). The LSCFT-0 material exhibits promising ORR with area-specific resistance (ASR) of 1.260, 0.580, 0.260, 0.100, and 0.06 Ω·cm2 at 600, 650, 700, 750, and 800 C, respectively. The performance is about 2 times higher than that of undoped La0.6Sr0.4Co0.4Fe0.6O3 with the ASR of 2.515, 1.191, 0.596, 0.320, and 0.181 Ω·cm2 from the lowest to the highest temperature. Through material characterization, it was found that the incorporated Ta occupied the B-site of the material, leading to the enhancement of the ORR activity. With the use of LSCFT-0 as the cathode material for anode-supported single-cell, the power density of > 1.0 W·cm−2 was obtained at a temperature < 800 °C. The results indicate that the CSSR-derived LSCFT is a promising cathode material for SOFCs.

A Review of X-ray Photoelectron Spectroscopy Technique to Analyze the Stability and Degradation Mechanism of Solid Oxide Fuel Cell Cathode Materials.

Nondestructive characterization of solid oxide fuel cell (SOFC) materials has drawn attention owing to the advances in instrumentation that enable in situ characterization during high-temperature cell operation. X-ray photoelectron spectroscopy (XPS) is widely used to investigate the surface of SOFC cathode materials because of its excellent chemical specificity and surface sensitivity. The XPS can be used to analyze the elemental composition and oxidation state of cathode layers from the surface to a depth of approximately 5–10 nm. Any change in the chemical state of the SOFC cathode at the surface affects the migration of oxygen ions to the cathode/electrolyte interface via the cathode layer and causes performance degradation. The objective of this article is to provide a comprehensive review of the adoption of XPS for the characterization of SOFC cathode materials to understand its degradation mechanism in absolute terms. The use of XPS to confirm the chemical stability at the interface and the enrichment of cations on the surface is reviewed. Finally, the strategies adopted to improve the structural stability and electrochemical performance of the LSCF cathode are also discussed.