Cathode For Intermediate Temperature Solid Oxide Research Articles

Layered perovskite-like Pr2-Er NiO4 as an improved cathode for intermediate-temperature solid oxide fuel cells

Layered perovskite-like Pr2-Er NiO4 as an improved cathode for intermediate-temperature solid oxide fuel cells

The effect of A-site deficiency on the performance of Fe-based perovskite La0.5Ba0.5-xFeO3-δ cathodes for intermediate-temperature solid oxide fuel cells

The effect of A-site deficiency on the performance of Fe-based perovskite La0.5Ba0.5-xFeO3-δ cathodes for intermediate-temperature solid oxide fuel cells

High entropy double perovskite cathodes with enhanced activity and operational stability for solid oxide fuel cells

Rare-earth site high entropy double perovskite oxides with different molar ratios have been evaluated as the cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFC). The effect of configuration entropy on crystal structure, electrical conductivity, electrochemical performance and stability are investigated. Our results reveal that the activity of all high entropy oxides show enhanced electrochemical activity. Among them, the equimolar one (HEO) exhibits the highest activity with a low polarization resistance of 0.05 Ω cm2 at 700 °C. Moreover, it exhibits excellent stability in the CO2-containing atmosphere. The enhanced activity and operational stability can be attributed to reduced surface Ba segregation and the formation of active and robust BaCoO3-δ nanoparticles on HEO surface, rather than BaCO3 and Co3O4 phases. This work indicates that configurational entropy engineering is very effective for rational surface composition regulation.

Ce-doped promotes the phase stability and electrochemical performance of SrCoO3-δ cathode for intermediate-temperature solid oxide fuel cells

The development of cathode with high oxygen reduction reaction (ORR) activity is crucial for intermediate-temperature solid oxide fuel cells (IT-SOFCs). SrCoO3-δ oxides, a mixed ion-electron conductivity (MIEC), are promising cathode materials. However, pure SrCoO3-δ exhibits a hexagonal or rhombohedral structure with poor electrical properties, limiting its application in IT-SOFCs. In this work, high-valence Ce4+ is doped at the A-site of SrCoO3-δ perovskite to improve the phase structural stability and electrochemical activity of SrCoO3-δ. The findings reveal that Ce4+ doping in small amounts significantly advances the conductivity and ORR activity due to enhanced structural stability. Among the series of samples, Sr0.95Ce0.05Co3-δ (SCC005) presents the best electrochemical performance. Moreover, the addition of Ce0.8Gd0.2O2-δ (GDC) further reduces polarization resistance by about ∼7 times. The peak power density of 1.3 W cm−2 is obtained at 750 °C for the SCC05-30%GDC cathode. The results indicate that A-site Ce doping is a promising strategy to enhance the ORR activity of SrCoO3-δ oxides.

Experimental study and first-principles calculation of enhanced electrochemical properties of Bi0.7Sr0.3FeO3-δ (BSFO) – La0.8Sr0.2MnO3-δ (LSM) composite cathodes for intermediate-temperature solid oxide fuel cells

In order to enhance the electrochemical performance of cobalt-free Bi0.7Sr0.3FeO3-δ (BSFO) cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs), a composite cathode consisting of BSFO and La0.8Sr0.2MnO3-δ (LSM) is developed. The optimized polarization resistance of the composite cathode (0.11 Ω cm2 at 800 °C) is found to be only 61 % that of pure BSFO (0.18 Ω cm2 at 800 °C), indicating a significant improvement in performance. The first-principles calculation indicates that the enhanced electrochemical performance is mainly due to the domain of low oxygen vacancy formation energies of BSFO-LSM-L interfaces (Evac, −3.63 eV) and LSM (Evac, −3.11 eV). The anode-supported single cell of NiO-SDC/SDC/BSFO－LSM shows a peak power density of 825.83 mW cm−2 at 800 °C using wet H2 (∼3 vol% H2O) as fuels and ambient air as oxidants. In addition, the single cell exhibits a good stability at the electric current density 400 mA cm−2 for 50 h measured at 650 °C.

The investigation of co-assembled high-performance (Ba, Sm/Sr)(Co, Zr)O3-δ composite perovskite cathodes for intermediate-temperature solid oxide fuel cell

The cobalt-based perovskites are the most common solid oxide fuel cell (SOFC) cathode materials, which generally have the issues of thermal compatibility and performance at the reducing temperature. In this study, two Ba0.5(Sm/Sr)0.5Co0.8Zr0.2O3-δ (BSmCZ/BSrCZ) perovskite composites were synthesized using a smart co-assembled method, which were primarily composed of cubic doped-BaZrO3 and hexagonal doped-BaCoO3 perovskites. Both BSmCZ and BSrCZ composites exhibited more suited thermal expansion coefficient (12.8 × 10-6 and 13.9 × 10-6 K−1) to the electrolyte, nanostructure with extensive heterointerfaces and excellent cathode|electrolyte interfaces. Compared to BSrCZ composite, the BSmCZ composite possessed a relatively higher content (65 %) of activated oxygen species and higher electrical conductivity (70.7 S cm−1). The cells with two composite cathodes could achieve the remarkable maximum power density, especially for BSmCZ composite cathode of 2.00–1.11 W∙cm−2 at 800–650 °C. The electrochemical analysis revealed that the BSmCZ composite cathode demonstrated the enhanced surficial oxygen catalysis processes, which could benefit from the active oxygen species and heterointerface.

Cobalt-free perovskite La0.6Ba0.4Ni0.2Fe0.8-xTixO3-δ(x=0–0.3) as cathode for intermediate-temperature solid oxide fuel cells

Developing effective cathode materials with superior electrocatalytic properties is crucial for advancing the practical application of solid oxide fuel cells. In this study, we successfully synthesized a series of cathode materials by introducing Ti into La0.6Ba0.4Ni0.2Fe0.8-xTixO3-δ(x = 0, 0.1, 0.2, 0.3) and conducted a comprehensive investigation of their physical and electrochemical characteristics. Our research revealed that the introduction of Ti into these materials led to a significant improvement in electrocatalytic activity and overall electrochemical performance. Importantly, these enhancements were achieved while maintaining an optimal thermal expansion coefficient and exceptional electrode stability. Among the various samples examined, the La0.6Ba0.4Ni0.2Fe0.7Ti0.1O3-δ cathode material stood out with the lowest polarization resistance recorded at 0.153 Ω cm2 and the highest power density achieved at 800 °C, reaching an impressive 1068 mW/cm2. Furthermore, our long-term stability tests demonstrated that these cells exhibited remarkable electrode stability, with no significant deterioration in electrochemical performance observed over a testing period of 50 h. Based on these findings, we propose that La0.6Ba0.4Ni0.2Fe0.7Ti0.1O3-δ holds great promise as a potential cathode material for solid oxide fuel cells.

Surface modulated B-site doping of PrBa0.5Sr0.5Co2-xFexO5+δ as highly efficient cathode for intermediate-temperature solid oxide fuel cells

Layered perovskite oxides (PrBaCo2O5+δ) have gained widespread interest as promising electrodes in intermediate-temperature solid oxide fuel cells (IT-SOFCs) because of their excellent oxygen diffusion and transport performance. However, it remains a great challenge to simultaneously realize thermal match and sufficient operational stability in existing IT-SOFCs. Herein, the layered perovskite PrBa0.5Sr0.5Co2-xFexO5+δ (PBSCFx) with strong oxygen reduction reaction (ORR) activity in half-cell and high power density in single cell was designed by partial substitution of Co with Fe. A systematic and comprehensive elaboration on the composition-structure-property relationships of PBSCFx was proposed. Furthermore, the complex electrochemical behavior of the single cell was investigated using equivalent circuit method (ECM) and distribution of relaxation time (DRT). Impressively, the polarization impedance of PBSCF05 (x = 0.5) is only 0.037 Ω·cm2 (T = 750 °C). The single cell with PBSCF05-GDC as the cathode can reach the maximum power density of 0.996 W/cm2 (T = 800 °C), and exhibits good stability in 216 h of long-term operation (T = 750 °C). The superior electrochemical performance of PBSCF05 is mainly attributed to the reduction of high frequency and intermediate frequency polarization resistance, which corresponds to the enhanced transfer process of oxygen ions, oxygen surface exchange and charge transfer process. This work highlights a simple B-site doping strategy to achieve the thermal match in IT-SOFCs, and furthermore, it expands the opportunities for effective utilization of ECM and DRT technology in the high-performance of IT-SOFCs.

Novel and high-performance (La,Sr)MnO3 based composite cathodes for intermediate-temperature solid oxide fuel cells

Novel and high-performance (La,Sr)MnO3 based composite cathodes for intermediate-temperature solid oxide fuel cells

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).

Effects of Bi-doping on structure and properties of YBaCo2O5+δ layered perovskite cathode for intermediate-temperature solid oxide fuel cells

Layered perovskite oxides, Y1–xBixBaCo2O5+δ (YBBCx, x = 0.0–0.2) were investigated as cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs). XRD results indicate the YBBCx could be indexed to a tetragonal phase with trace of 3 × 3 × 1 superstructure configuration. No significant change in thermal expansion coefficients (TECs) was detected with the Bi-doping, and the TECs were 15.7–16.8 × 10−6 K−1 at 100–935 °C in air. Although the Bi-doping results in a decrease in conductivity of the YBBCx, the x = 0.2 sample still shows higher conductivity than that of a standard SOFC cathode (∼100 S cm−1). Additionally, the Bi-doping leads to an enhancement in the electrochemical performance mainly due to improved ion and electron charge transfers. Among the YBBCx compositions, the YBBC0.2 cathode shows the lowest polarization resistance (Rp) of 0.034 Ω cm2 at 700 °C. For a single cell with 300 µm thick La0.9Sr0.1Ga0.8Mg0.2O3–δ (LSGM) and YBBC0.2 cathode, a peak power density (Pmax) of 537 mW cm−2 at 700 °C was achieved with no significant deterioration in performance after a 100–h testing.

Study on microstructure and physical properties of Ba0.5Sr0.5Fe1−xCuxO3−δ–Ce0.8Sm0.15Ca0.05O1.875 cathode materials used in solid oxide fuel cell

Ba0.5Sr0.5Fe1−xCuxO3−δ (BSFCu) and BSFCu–Ce0.8Sm0.15Ca0.05O1.875 (SCDC) were prepared by solid-state reaction and sol-gel method, respectively. The possibility of BSFCu−SCDC composites as cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs) was investigated. The results show that BSFCu has a cubic BaFeO3 structure and no secondary phase. BSFCu−SCDC has cubic BaFeO3 and Ce0.8Sm0.2O1.9 structures, and BaCeO3 secondary phase. The polarization surface specific resistance (ASRRP) of BSFCu increases with increasing Cu doping. For BSFCu–SCDC, 7BSFCu10–3SCDC has the smallest ASRRP (0.106 Ω cm2, 800 °C) at 800 °C–750 °C; at 600 °C − 700 °C, 6BSFCu10–4SCDC has the smallest ASRRP (1.043 Ω cm2, 600 °C). The maximum exchange current densities of 7BSFCu10–3SCDC and 6BSFCu10–4SCDC are about 0.219 and 0.083 A cm−2 at 800 °C and 700 °C, respectively. Compared with BSFCu, 6BSFCu10–4SCDC has a lower overpotential, which shows better electrocatalytic activity, so it can increase the energy efficiency when applied to IT-SOFC.

Enabling extraordinary oxygen reduction reaction activity of dual alkaline earth-substituted perovskite cathodes for intermediate-temperature solid oxide fuel cells

Dual alkaline earth-substituted Pr0.94Ba1–2xSrxCaxCo2O5+δ perovskites are evaluated as potential cathodes for intermediate-temperature solid oxide fuel cells. When incorporating Sr2+ and Ca2+ into the lattice, the phase transformation from tetragonal layered perovskite to simple cubic perovskite can be identified. Benefitting from enhanced electrical conductivity, oxygen surface exchange and ionic diffusion rates, the as-prepared perovskite catalysts demonstrate highly electrocatalytic activity for oxygen reduction reaction. The Pr0.94Ba0.6Sr0.2Ca0.2Co2O5+δ cathode exhibits an area-specific resistance of 0.025 Ω cm2 at 700 °C, approximately decreased by = 60% relative to the pristine Pr0.94BaCo2O5+δ. It is discovered that Sr2+ and Ca2+ co-substituting lowers the charge transfer energy, as well as oxygen adsorption energy. Furthermore, the Pr0.94Ba0.6Sr0.2Ca0.2Co2O5+δ cathode-based fuel cell delivers a peak power density of 1194 mW cm−2 at 700 °C, along with outstanding short-term stability over a period of 160 h. Our results highlight a strategy of dual alkaline earth substitution for rationally designing the perovskite electrocatalysts.

Interface engineering of an electrospun nanofiber-based composite cathode for intermediate-temperature solid oxide fuel cells

Sluggish oxygen reduction reaction (ORR) kinetics are a major obstacle to developing intermediate-temperature solid-oxide fuel cells (IT-SOFCs). In particular, engineering the anion defect concentration at an interface between the cathode and electrolyte is important for facilitating ORR kinetics and hence improving the electrochemical performance. We developed the yttria-stabilized zirconia (YSZ) nanofiber (NF)-based composite cathode, where the oxygen vacancy concentration is controlled by varying the dopant cation (Y2O3) ratio in the YSZ NFs. The composite cathode with the optimized oxygen vacancy concentration exhibits maximum power densities of 2.66 and 1.51 W cm−2 at 700 and 600 °C, respectively, with excellent thermal stability at 700 °C over 500 h under 1.0 A cm−2. Electrochemical impedance spectroscopy and distribution of relaxation time analysis revealed that the high oxygen vacancy concentration in the NF-based scaffold facilitates the charge transfer and incorporation reaction occurred at the interfaces between the cathode and electrolyte. Our results demonstrate the high feasibility and potential of interface engineering for achieving IT-SOFCs with higher performance and stability.

Development of La1.7Ca0.3Ni1-yCuyO4+δ Materials for Oxygen Permeation Membranes and Cathodes for Intermediate-Temperature Solid Oxide Fuel Cells.

The La1.7Ca0.3Ni1-yCuyO4+δ (y = 0.0-0.4) nickelates, synthesized via a solid-state reaction method, are investigated as prospective materials for oxygen permeation membranes and IT-SOFC cathodes. The obtained oxides are single-phase and possess a tetragonal structure (I4/mmm sp. gr.). The unit cell parameter c and the cell volume increase with Cu-substitution. The interstitial oxygen content and total conductivity decrease with Cu-substitution. The low concentration of mobile interstitial oxygen ions results in a limited oxygen permeability of Cu-substituted La1.7Ca0.3NiO4+δ ceramic membranes. However, increasing the Cu content over y = 0.2 induces two beneficial effects: enhancement of the electrochemical activity of the La1.7Ca0.3Ni1-yCuyO4+δ (y = 0.0; 0.2; 0.4) electrodes and decreasing the sintering temperature from 1200 °C to 900 °C. Enhanced electrode activity is due to better sintering properties of the developed materials ensuring excellent adhesion and facilitating the charge transfer at the electrode/electrolyte interface and, probably, faster oxygen exchange in Cu-rich materials. The polarization resistance of the La1.7Ca0.3Ni1.6Cu0.4O4+δ electrode on the Ce0.8Sm0.2O1.9 electrolyte is as low as 0.15 Ω cm2 and 1.95 Ω cm2 at 850 °C and 700 °C in air, respectively. The results of the present work demonstrate that the developed La1.7Ca0.3Ni0.6Cu0.4O4+δ-based electrode can be considered as a potential cathode for intermediate-temperature solid oxide fuel cells.

Ekspansi Termal, Oxygen Content, dan Sifat Elektrokimia Oksida SmBa0.5Sr0.5Co2O5+δ (70%) + SDC (30%) Sebagai Katoda SOFC

The thermal properties of the double perovskite SmBa0.5Sr0.5Co2O5+δ (70%) + SDC (30%) have been investigated as potential cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFC). This study also includes the oxygen content and electrochemical performance of long-term tests carried out to evaluate the electrochemical stability. Cathode powder is fabricated by a simple and relatively inexpensive solid-state reaction. Oxygen content decreased gradually from room temperature to 800oC by 18.3%. Doping 30% SDC into SBSC oxide can reduce the thermal expansion coefficients (TEC) value from 19.80 x 10-6 (K-1) to 18.17 x 10-6 (K-1) or a decrease of 8.23%. The activation energy (Ea) identified by the electrochemical impedance spectroscopy (EIS), low field (LF), and high field (HF) techniques were 125.3 kJ mol-1, 60.6 kJ mol-1, and 62.5 kJ mol-1, respectively. The SBSC73|SDC|SBSC73 symmetric cell test for 96 hours at 600oC showed an increase in the average polarization resistance value of 0.30% h-1. The cathode grains are evenly distributed with a size of 2-3 µm and tend to be porous. These results exhibit that SmBa0.5Sr0.5Co2O5+δ (70%) + SDC (30%) is a promising cathode material for IT-SOFCs.

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.

Addressing the origin of highly catalytic activity of A-site Sr-doped perovskite cathodes for intermediate-temperature solid oxide fuel cells

Highly active cathode materials are crucial to accelerating the commercialization of intermediate-temperature solid oxide fuel cells (IT-SOFCs). Herein, Sr-doped Pr0.94Ba1-xSrxCo2O5+δ (PBSxCO) perovskite oxides are evaluated by experimental and theoretical studies. The phase transformation from tetragonal layered double perovskite to cubic simple perovskite can be identified with increasing the Sr fraction. Benefiting from enhanced electrical conductivity and oxygen surface rate, the PBSxCO catalysts deliver excellent electrochemical performance, as evidenced by symmetrical and completed cells test. Among all compositions, the Pr0.94Ba0.7Sr0.3Co2O5+δ (PBS0.3CO) cathode has the lowest polarization resistance (Rp) of 0.031 Ω cm2 at 700 °C. The PBS0.3CO cathode-based fuel cell produces a peak power density of 1077 mW cm−2, along with a steady operating for 130 h at 700 °C. From the density functional theoretical (DFT) calculations, it is discovered that stronger Co 3d-O 2p hybridization is recognized in the Sr substituting model compared with undoped one. Furthermore, the decreased free energy for oxygen adsorption may facilitate the oxygen reduction reaction (ORR) kinetics. These findings highlight the origin of optimal ORR activity induced by A-site alkaline earth doping in the perovskite catalysts, endowing the rational design of oxide catalysts.

Self-assembled, high-performing cobalt-free Ba0.5A0.5Fe0.8Zr0.2O3-δ (A=Sr2+/Sm3+) composite cathode for intermediate-temperature solid oxide fuel cells

In this study, cost-effective cathode materials with high catalysis activity for oxygen reduction reaction (ORR) are proposed for use in intermediate-temperature solid oxide fuel cells. Cobalt-free Ba0.5A0.5Fe0.8Zr0.2O3-δ (A=Sr2+/Sm3+, BSrFZ/BSmFZ) composites were synthesised using a smart self-assembled method that primarily utilised doped-BaZrO3 and doped-BaFeO3 cubic perovskites. The BSrFZ composite possesses a higher doped-BaFeO3 (75 wt%) content, which facilitates the formation of oxygen vacancies and ORR catalysis. The BSmFZ composite exhibits a relatively higher content of doped-BaZrO3 (31 wt%) than that of the BSrFZ composite, which is more suited to the electrolyte and improves the thermal expansion coefficient (16.0 × 10−6 K−1). Both composite cathodes exhibit nano- and micro-particles with extensive heterointerfaces and excellent cathode|electrolyte interfaces, which can assist the surface catalysis and oxygen species transport. The cell with a BSrFZ composite cathode achieved a higher maximum power density of 1.64 W cm−2 at 750 °C compared to that of the cell with a BSmFZ composite cathode that had a maximum power density of 0.99 W cm−2. The electrochemical analysis revealed that the BSrFZ composite cathode demonstrated enhanced oxygen adsorption dissociation and oxygen species reduction processes, which benefit from its enriched oxygen vacancies and high surface and heterointerface activities.

Synthesis and characterization of fibrous La0.8Sr0.2Fe1-xCuxO3-δ cathode for intermediate-temperature solid oxide fuel cells

Aiming to offer a high-performance Co-free cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs), a series of La0.8Sr0.2Fe1-xCuxO3-δ (LSFCux, x = 0.0–0.3) nanofiber cathodes were synthesized by the electrospinning method. The effects of various Cu doping amounts on the crystal structure, fiber morphology, and electrochemical performance of LSF nanofiber cathode materials were investigated. The results indicate that after being calcined at 800 °C for 2 h, the perovskite structure samples with a high degree of crystallinity are obtained. The morphology of electrospun nanofibers is continuous, and the average diameter of nanofibers is about 110 nm. In addition, the La0.8Sr0.2Fe0.8Cu0.2O3-δ (LSFCu2) fiber cathode displays the optimal electrochemical performance, and the polarization resistance (Rp) is 0.674 Ω cm2 at 650 °C. The doping of Cu transforms the main control step of the low-frequency band from dissociation of oxygen molecules to charge transfer on the electrode, and the maximum power density (Pm) of the Ni-SDC/SDC/LSFCu2 single cell reaches 362 mW cm-2 at 650 °C.