A promising strontium and cobalt-free air electrode Pr1-xCaxFeO3-δ for solid oxide electrolysis cell

A promising strontium and cobalt-free ferrite Pr_1-xCa_xFeO_3-δ (PCF, x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) has been synthesized successfully by glycine-nitrate combustion method and used as the air electrode of solid oxide electrolysis cell (SOEC) for steam electrolysis. The crystal structure and electricity conductivity of PCF are investigated in detail. According to the conductivity test, Pr_0.6Ca_0.4FeO_3-δ (PCF64) with higher conductivity is selected as the air electrode to preparing the single cell with structure of PCF64|GDC|SSZ|YSZ-NiO. Under SOFC mode, the maximum power density of the single cell is 462.93 mW cm⁻² at 800 °C with hydrogen as fuel. Under SOEC mode, the current density reaches 277.14 mA cm⁻² and the corresponding hydrogen production rates is 115.84 mL cm⁻² h⁻¹ at 800 °C at 1.3 V. In the 10 h short-term stability test, the cell shows good electrolysis stability.     

Leveraging in-situ formation of Ni–Fe nanoparticles to promote the catalytic performance of Ruddlesden-Popper based electrode for symmetrical solid oxide fuel cells

Ruddlesden?Popper layered oxide, La_0.25Sr_2.75FeNiO_7-δ (LSFN) is evaluated as a potential electrode material for symmetrical solid oxide fuel cells. The in-situ formation of Ni–Fe alloy nanoparticles on the LSFN surface in reducing atmosphere can be believed to enhance the activity towards hydrogen oxidation reaction. LSFN exhibit maximum conductivity of 221.2 S/cm and 0.206 S/cm in air and hydrogen environment. Furthermore, LSFN is mixed with GDC powder to form a composite electrode for symmetric solid oxide fuel cells (SSOFC). Results show that with the combination of GDC, the maximum power density of YSZ-based SSOFC enlarges from 232.3 mW cm^?2 to 348.5 mW cm^?2, and related polarization resistance reduces from 0.359 Ω cm² to 0.108 Ω cm². The improved performance is attributed to the enlarged triple-phase boundary with the mixing of GDC. In addition, YSZ-based SSOFC with the LSFN-GDC composite electrode shows a stable performance in intermediate-temperature SSOFCs within 200 h, which indicates that LSFN-GDC composite material is a prospective symmetrical electrode for SSOFC.     

Performance and structural stability of Gd0.2Ce0.8O1.9 infiltrated La0.8Sr0.2MnO3 nano-structured oxygen electrodes of solid oxide electrolysis cells

Effect of Gd_0.2Ce_0.8O_1.9 (GDC) infiltration on the performance and stability of La_0.8Sr_0.2MnO₃ (LSM) oxygen electrodes on Y₂O₃-stabilized ZrO₂ (YSZ) electrolyte has been studied in detail under solid oxide electrolysis cell (SOEC) operating conditions at 800 °C. The incorporation of GDC nanoparticles significantly enhances the electrocatalytic activity for oxygen oxidation reaction on LSM electrodes. Electrode polarization resistance of pristine LSM electrode is 8.2 Ω cm² at 800 °C and decreases to 0.39 and 0.09 Ω cm² after the infiltration of 0.5 and 1.5 mg cm⁻² GDC, respectively. The stability of LSM oxygen electrodes under the SOEC operating conditions is also significantly increased by the GDC infiltration. A 2.0 mg cm⁻² GDC infiltrated LSM electrode shows an excellent stability under the anodic current passage at 500 mA cm⁻² and 800 °C for 100 h. The infiltrated GDC nanoparticles effectively shift the reaction sites from the LSM electrode/YSZ electrolyte interface to the LSM grains/GDC nanoparticle interface in the bulk of the electrode, effectively mitigating the delamination at the LSM/YSZ interface. The results demonstrate that the GDC infiltration is an effective approach to enhance the structural integrity and thus to achieve the high activity and excellent stability of LSM-based oxygen electrode under the SOEC operating conditions.     

LSCM-GDC as composite cathodes for high temperature steam electrolysis: Performance optimization by composition and microstructure tailoring

The double-doped perovskite La_0·75Sr_0·25Cr_0·5Mn_0·5O_3-δ (LSCM) is a promising cathode material for solid oxide electrolysis cells (SOECs), but the poor catalytic activity limits its application. In this work, LSCM-Gd_0.2Ce_0·8O_2-δ (GDC) bilayer cathodes are successfully prepared for high temperature steam electrolysis. The moderate addition of GDC to LSCM electrode improves the cell performance due to the formation of more oxygen vacancies and increased H₂O adsorption capability. Moreover, particle size graded cathodes are further prepared based on the optimal composition, and the optimized cell achieves a remarkable current density of 2.36 A cm^?2 at ?0.1 V and 800 °C under non-reducing conditions. The well-connected and porous network effectively extends the length of triple-phase boundaries (TPBs) and facilitates the gas diffusion inside the electrode. Therefore, doping with a certain amount of GDC and optimizing the microstructure of electrodes are effective ways to enhance the electrocatalytic activity of the conventional LSCM-GDC cathode.     

Bi-doped La1.5Sr0.5Ni0.5Mn0.5O4+δ as an efficient air electrode material for SOEC

Bi-doped La_1.5-xBi_xSr_0.5Ni_0.5Mn_0.5O_4+δ (LBSNM-x, x = 0, 0.05, 0.1, 0.15) was investigated as a potential air electrode for solid oxide electrolysis cell (SOEC). The effect of Bi doping on the structure, electrical conductivity, chemical compatibility with GDC electrolyte, electrochemical performance and thermal expansion coefficients (TECs) were investigated. XRD characterization results show that the solid solution content of Bi is less than or equal to 0.1. XPS characterization results indicate that Bi doping increases the oxygen vacancy content of LBSNM-x air electrode and thus greatly benefits its oxygen evolution reaction. Among the Bi-doped samples, LBSNM-0.1 electrode has the best electrochemical performance with its lowest Rp (polarization resistance) of 0.28 Ω cm² at 800 °C based on LBSNM-0.1/GDC half-cell. LBSNM-0.1 single cell with 70%CO₂ + 30%CO fuel gas feed on the fuel electrode has achieved current density of 811 mA cm⁻² at 800 °C and 1.4 V, a 62.2% increase relative to that of LSNM single cell. In addition, LBSNM-0.1 single cell exhibits excellent stability at 800 °C and 1.3 V with 70%CO₂ + 30%CO feed gas on the fuel electrode. These results prove that Bi-doped LBSNM-0.1 is an efficient air electrode for SOEC.     

Effects of sulfur poisoning on degradation phenomena in oxygen electrodes of solid oxide electrolysis cells and solid oxide fuel cells

The durabilities of a single solid oxide electrolysis cell (SOEC) and a solid oxide fuel cell (SOFC) operating at 0.3 A cm^?2 and 973 K under different air supply conditions were investigated. In the SOEC, S penetration was observed mainly at the gadolinium-doped ceria (CGO) electrolyte/lanthanum strontium cobalt oxide (LSC) oxygen electrode interface. In contrast, during SOFC operation, S was distributed widely within the LSC. The reaction governing S penetration into the LSC is an oxidizing one. Thus, it is likely that the high oxygen partial pressure at the CGO electrolyte/LSC oxygen electrode interface accelerated the penetration of S. When air was supplied using an activated carbon filter during SOEC operation, the degradation rate decreased to 0.6% kh^?1 within 3000 h. Finally, the results of accelerated tests performed using air containing 0.2 ppm SO₂ suggested that the effect of S poisoning was greater during SOEC operation than during SOFC operation.     

Methane internal steam reforming in solid oxide fuel cells at intermediate temperatures

The internal steam reforming of methane (CH₄) on conventional solid oxide fuel cell (SOFC) anode (nickel-yttria stabilized zirconia or Ni-YSZ) offers significant advantages compared to the external reforming process. However, the technology is currently facing some major issues such as coking and oxidation of anode during operation. Here we report a low-temperature sinterable catalyst, Ce_0·77Ni_0·2Mn_0·03O_2-δ (CNMnO), applied on top of Ni-YSZ to perform the steam reforming reaction. A single cell with CNMnO/Ni-YSZ/YSZ/GDC/LSC configuration produces a peak power density of 492 mW cm^?2 in wet hydrogen and 371 mW cm^?2 in wet methane, at 600 °C. The cell also shows exceptional durability against Ni oxidation when tested in wet methane under 0.2 A cm^?2 for 100 h. The improved performance and durability of the catalyst layer has been attributed to the nanosized precipitated Ni and Mn particles distributed on the surface of individual CNMnO particles.     

Synthesis and characterization of Nanocrystalline Ba0·6Sr0·4Co0·8Fe0·2O3 for application as an efficient anode in solid oxide electrolyser cell

Nanocrystalline Ba_0·6Sr_0·4Co_0·8Fe_0·2O₃ (BSCF-6482) powder is synthesized by combustion synthesis technique. Powder calcined at 1000 °C reveals phase pure cubic perovskite. Transmission electron microscopic (TEM) analysis exhibits soft agglomerates of average size ∼50 nm wherein interplanar spacing for (110) and (221) resembles to the cubic lattice. While DC electrical conductivity of 23 S cm⁻¹@800 °C is observed, interfacial polarization measured by electrochemical impedance spectroscopy is found to be the least @850 °C (0.18 Ω cm²). Cell performance has been compared among BSCF-6482, BSCF-5582 and LSCF-6482 mixed ionic and electronic conducting (MIEC) and conventional electrode (LSM). Higher performance (1.37 A/cm²@1.3 V,800 °C) with high hydrogen generation rate (0.57 Nl/cm²/h) is found during steam electrolysis with cell fabricated using BSCF-6482 having minimal area specific resistance 0.33 Ω cm². Under similar operating condition, BSCF-5582, LSCF-6482 and LSM exhibit hydrogen generation rate of 0.35, 0.28 and 0.23 Nl/cm²/h respectively. Cell microstructure is clinically correlated with the higher reactivity of BSCF-6482 air electrode in steam electrolysis.     

Gadolinium doped ceria-impregnated nickel-yttria stabilised zirconia cathode for solid oxide electrolysis cell

Steam electrolysis (H₂O → H₂ + 0.5O₂) was investigated in solid oxide electrolysis cells (SOECs). The electrochemical performance of GDC-impregnated Ni-YSZ and 0.5% wt Rh-GDC-impregnated Ni-YSZ was compared to a composite Ni-YSZ and Ni-GDC electrode using a three-electrode set-up. The electrocatalytic activity in electrolysis mode of the Ni-YSZ electrode was enhanced by GDC impregnation. The Rh-GDC-impregnated Ni-YSZ exhibited significantly improved performance, and the electrode exhibited comparable performance between the SOEC and SOFC modes, close to the performance of the composite Ni-GDC electrode. The performance and durability of a single cell GDC-impregnated Ni-YSZ/YSZ/LSM-YSZ with an H₂ electrode support were investigated. The cell performance increased with increasing temperature (700 °C-800 °C) and exhibited comparable performance with variation of the steam-to-hydrogen ratio (50/50 to 90/10). The durability in the electrolysis mode of the Ni-YSZ/YSZ/LSM-YSZ cell was also significantly improved by the GDC impregnation (200 h, 0.1 A/cm², 800 °C, H₂O/H₂ = 70/30).     

A promising Bi-doped La0.8Sr0.2Ni0.2Fe0.8O3-δ oxygen electrode for reversible solid oxide cells

Reversible solid oxide cells (RSOCs) are clean and effective electrochemical conversion devices that require highly active electrodes and stable electrochemical performance for the practical application. Herein, we investigate a series of La_0.8-xBi_xSr_0.2Ni_0.2Fe_0.8O_3-δ (LBSNF-x, x = 0.0, 0.05, 0.1, 0.15) oxides as the potential oxygen electrode material for RSOCs. The properties of electrical conductivity, thermal expansion coefficient, and chemical compatibility with the Ce_0.9Gd_0.1O_1.95 (GDC) barrier layer of LBSNF-x oxides are evaluated. When LBSNF-0.1 and GDC forms a composite oxygen electrode with the ratio of 7:3, it shows the lowest polarization resistance with fastest oxygen reduction reaction activity in the symmetrical cell test. Then the cell with the configuration of Ni-YSZ/YSZ/GDC/LBSNF-0.1-GDC was prepared and evaluated both in fuel cell (FC) and electrolysis cell (EC) mode. The maximum power density of 824 mW cm⁻² is obtained at 800 °C in FC mode, and current density of 1.20 A cm⁻² is achieved under 50% steam content at 1.3 V in EC mode. Additionally, the cell exhibits good stability both in FC and EC mode after 80 h test at 700 °C. The results of this work provide a strong support for application of the LBSNF-0.1-GDC oxygen electrode for reversible solid oxide cells.     

Comparison of ceria and zirconia based electrolytes for solid oxide electrolysis cells

Steam electrolysis for hydrogen production is investigated in solid oxide electrolysis cell (SOEC). Sc³⁺, Ce⁴⁺, and Gd³⁺ are doped in zirconia (SCGZ) and compared with yttria stabilized zirconia (YSZ) and gadolinium doped ceria (GDC) electrolyte. Electrolyte-supported cells are fabricated. The SCGZ and YSZ electrolytes are dense with >95% relative density while GDC is less densified. The activation energy of conduction of the SCGZ electrolyte is the lowest at 65.58 kJ mol^?1 although phase transformation is detected after electrolyte fabrication process. Cathode-supported cell having SCGZ electrolyte (Ni-SCGZ/SCGZ/BSCF) shows the highest electrochemical performance. Durability test of the cells in electrolysis mode is carried out over 60 h (0.3 A cm^?2, 1073 K, H₂O to H₂ ratio of 70:30). Significant performance degradation of Ni-GDC/YSZ/GDC/BSCF cell is observed (0.0057 V h^?1) whereas the performance of Ni-YSZ/YSZ/BSCF and Ni-SCGZ/SCGZ/BSCF are rather stable under the same operating conditions. The BSCF remains attaching to the SCGZ electrolyte and additional phase transformation is not observed after prolong operation.     

The effect of gas compositions on the performance and durability of solid oxide electrolysis cells

High-temperature electrolysis with various gas compositions has been performed to investigate the effects of the hydrogen partial pressure and the humidity generated by the steam electrode on the performance and durability of solid oxide electrolysis cells. The power density of the button cell used in this research is 0.48 W cm⁻² at 750 °C, and the flow rates of the air and humidified hydrogen are 100 cc min⁻¹. By changing the flow ratio of H₂:Ar:H₂O(g) from 10:0:4 to 1:9:4, the cell's OCV decreases from 0.973 V to 0.877 V, and the charge transfer resistance increases from 1.126 Ω cm² to 1.645 Ω cm². The close relationship between the conversion efficiency of high-temperature electrolysis and steam composition is evident in the increase in the cell's charge transfer resistance from 0.381 Ω cm² to 1.056 Ω cm² as the steam content changed from 40 vol% to 3 vol%. Although the electrochemical splitting of water is stimulated in the short term by excessive steam flow, the Ni-YSZ electrodes have been damaged by the steam electrode's low H₂ partial pressure. Consequently, the steam electrode's gas composition must be optimized in the long-term because of the trade-off between performance and durability, which depends on the water concentration of the steam electrodes.     

La0.75Sr0.25Cr0.5Mn0.5O3 as hydrogen electrode for solid oxide electrolysis cells

La_0.75Sr_0.25Cr_0.5Mn_0.5O₃ (LSCM) has been applied as hydrogen electrode (cathode) material in solid oxide electrolysis cells operating with different steam concentrations (20, 40, 60 and 80 vol.% absolute humidity (AH)) using 40 sccm H₂ carrier gas at 800, 850 and 900 °C, respectively. Impedance spectra and voltage-current curves were measured as a function of cell electrolysis current density and steam concentration to characterize the cell performance. The cell resistance decreased with the increase in electrolysis current density while increased with the increase in steam concentration under the same electrolysis current density. At 1.6 V applied electrolysis voltage, the maximum consumed current density increased from 431 mA cm⁻² for 20 vol.% AH to 593 mA cm⁻² for 80 vol.% AH at 850 °C. Polarization and impedance spectra experiments revealed that LSCM-YSZ hydrogen electrode played a major role in the electrolysis reaction.     

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, Pr₂NiO_4+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 La_0.6Sr_0.4CoO_3-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 O^2? in the cathode and thus improves the ORR activity of the material. When the impregnation concentration of LSC reached C_LSC = 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.     

Highly active and stable A-site Pr-doped LaSrCrMnO-based fuel electrode for direct CO2 solid oxide electrolyzer cells

Direct CO₂ electrolysis has been explored as a means to store renewable energy and produce renewable fuels. La chromate-based perovskite oxides have attracted great attention as fuel electrode materials for solid oxide electrolyzer cells. However, the electrochemical catalytic activity of such oxides is relatively low, and their stability has not been confirmed. In this study, Pr is doped into La_0.75Sr_0.25Cr_0.5Mn_0.5O_3-δ (LSCM) and the applicability of the resulting fuel electrode to direct CO₂ electrolysis is investigated. The polarization resistance of the resulting electrode at 800 °C is decreased by 25%. Distribution function of relaxation times analysis indicates that the observed improvements may be attributed to increased oxygen ion conductivity. A full cell of Pr-doped LSCM-gadolinium-doped ceria (GDC)|scandia-stabilized zirconia|La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ-GDC achieves an electrolysis current of 0.5 A cm⁻² at 1.36 V and a Faradaic efficiency close to 100%. Short-term (210 h) stability testing of the cell under an electrolysis current of 0.5 A cm⁻² at 800 °C with pure CO₂ as the feedstock reveals a decrease in applied voltage at a rate of 7 mV kh⁻¹, thereby indicating excellent stability. Thus, given its satisfactory performance and stability, the Pr-doped LSCM electrode may be considered a promising candidate material for direct CO₂ electrolysis.     

Robust Ni-doped Ruddlesden-popper (La,Sr)Fe1-xNixO4+δ oxide as solid oxide cells fuel electrode for CO2 electrolysis

Ruddlesden-popper (La, Sr)FeO_4+δ perovskite oxide with excellent redox stability shows insufficient electrochemical catalytic activity for CO₂ reduction because of low conductivity and oxygen vacancy concentration. In this work, Ni modified (La, Sr)Fe_1-xNi_xO_4+δ cathode was developed to improve the conductivity and catalytic activity for CO₂ electrolysis. The introduction of the Ni element significantly increases the conductivity of (La, Sr)FeO_4+δ perovskite oxide in both air and 50%CO₂/CO due to the increasing charge carrier's concentration. Furthermore, the symmetric cell with (La, Sr)Fe_0·9Ni_0·1O_4+δ (RPLSFNi0.1) electrode exhibits the lowest polarization resistance in 50%CO₂/CO, suggesting that the RPLSFNi0.1 electrode has the best catalytic activity for CO₂ electrolysis. Moreover, the addition of Sm_0.2Ce_0·8O_2-δ (SDC) in RPLSFNi0.1 electrode further enhances the electrochemical performance, and the current density of ?1170 mA cm^?2 is obtained at 850 °C and 1.5 V. In addition, the electrolysis cell exhibits excellent reversible cycling operating stability between 0.6 V at fuel cell mode and 1.2 V at electrolysis mode, indicating that RPLSFNi0.1 is a robust cathode material for solid oxide cells (SOCs) fuel electrode.     

Ba0.9Co0.5Fe0.4Nb0.1O3−δ as novel oxygen electrode for solid oxide electrolysis cells

A novel perovskite oxide Ba_0.9Co_0.5Fe_0.4Nb_0.1O_3−δ (BCFN) was prepared and characterized as oxygen electrode for solid oxide electrolysis cells (SOECs) using La_0.8Sr_0.2Ga_0.83Mg_0.17O_3−δ (LSGM) as electrolyte. Symmetrical half-cell study shows that the polarization resistance of BCFN is only 0.08 Ω cm² at 750 °C in air. Electrochemical impedance spectra and voltage-current curves of the electrolysis cell with the configuration of BCFN|LSGM|La_0.4Ce_0.6O_2−x|Ni-Ce_0.9Gd_0.1O_1.95 were measured as a function of operating temperature and steam concentrations to characterize the electrolysis cell performances. Under an applied electrolysis voltage of 1.5 V, the maximum consumed current density increased from 0.835 A cm⁻² at 700 °C to 3.237 A cm⁻² at 850 °C with 40 vol.% absolute humidity (AH), and the hydrogen generation rate of the cell can be up to 1352 mL cm⁻² h⁻¹ with 40 vol.% AH at 850 °C. Further, the electrolysis cell has showed very stable performance during a 200 h short-term electrolysis testing, indicating that BCFN can be a very promising candidate for the oxygen electrode of SOECs using LSGM electrolyte.     

Solid oxide cells with cermet of silver and gadolinium-doped-ceria symmetrical electrodes for high-performance power generation and water electrolysis

A cermet of silver and gadolinium-doped-ceria (Ag-GDC) is investigated as novel symmetrical electrode material for (ZrO₂)_0.92(Y₂O₃)_0.08 (YSZ) electrolyte-supported solid oxide cells (SOCs) operated in fuel cell (SOFC) and electrolysis (SOEC) modes. The electrochemical performances are evaluated by measuring the current density-voltage characteristics and impedance spectra of the SOCs. The activity of hydrogen and air electrodes is investigated by recording overpotential versus current density in symmetrical electrode cells, respectively in hydrogen and air, using a three-electrode method. Conventional hydrogen electrode, Ni-YSZ, and oxygen electrode, LSCF (La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ)-GDC, are tested as comparison. The results show that, as an oxygen electrode, Ag-GDC is more active than LSCF-GDC in catalyzing both oxygen reduction reaction (ORR) in an SOFC and oxygen evolution reaction (OER) in an SOEC. As a hydrogen electrode, Ag-GDC is more active than Ni-YSZ in catalyzing hydrogen oxidation reaction (HOR) in an SOFC and hydrogen evolution reaction (HER) in an SOEC, especially in high steam concentration. An SOC with symmetrical Ag-GDC electrodes operated in a fuel cell mode, with 3% H₂O humidified H₂ as the fuel, displays a peak power density of 395 mWcm^?2 at 800 °C. Its polarization resistance at open circuit voltage is 0.21 Ω cm². Ag-GDC electrode can be operated even at pure steam. An SOEC operated for electrolyzing 100% H₂O, the current density reaches 720 mA cm^?2 under 1.3 V at 800 °C.     

80,000 current on/off cycles in a one year long steam electrolysis test with a solid oxide cell

The current ON/OFF switching of a solid oxide electrolysis cell is treated as elementary step for power variation in a steam electrolyser system. If the cell voltage in the ON mode is adjusted to the thermal neutral voltage, heat generation remains zero in both modes, which largely facilitates the thermal management. To verify whether the cells withstand the switching, an electrolysis durability test with an electrolyte supported solid oxide cell was performed during one year at about 850 °C. The cell consisted of a 3YSZ electrolyte, CGO diffusion-barrier/adhesion layers, a lanthanum strontium cobaltite ferrite (LSCF) oxygen electrode, and a nickel/gadolinia-doped ceria (Ni/GDC) steam/hydrogen electrode. The test included two operation blocks with each 40,000 cycles of 2 min duration and a current density of −0.7 Acm⁻² in the ON mode (−0.07 Acm⁻² in OFF mode), as well as steady-state ON periods with 5800 h duration. Voltage degradation was 5 mV/1000 h (0.4%/1000 h) and the increase in the area specific resistance 7 mΩcm²/1000 h, without notable dependence on current cycling. Impedance spectroscopic results were in agreement with the only small switching transients seen in the cell voltage; moreover, they confirmed a dominating ohmic degradation together with minor contributions from gas conversion and reaction, respectively. No electrode delamination was detectable after scheduled test completion.     

Characterization of cation-ordered perovskite oxide LaBaCo2O5+δ as cathode of intermediate-temperature solid oxide fuel cells

A-site cation-ordered perovskite oxide LaBaCo₂O_5+δ (LBCO) was synthesized and evaluated as a cathode material of intermediate-temperature solid oxide fuel cells (IT-SOFCs). LBCO was structurally stable when calcined at 850 °C in air but transformed into cation-disordered structure at 1050 °C. LBCO showed chemical compatibility with Gd_0.1Ce_0.9O_1.95 (GDC) electrolyte at 850 °C and 1000 °C in air. Conductivity of LBCO firstly increased slightly with higher temperature to a maximum of 470 S cm⁻¹ at ∼250 °C and then decreased gradually with further increase in temperature. Electrochemical impedance spectra of the LBCO/GDC/LBCO symmetric cell were measured, and electrode reaction mechanism for the LBCO cathode was analyzed. The electrode polarization resistance of LBCO was mainly contributed by oxygen ionic transfer across the cathode/electrolyte interface and oxygen atom diffusion-electronic charge transfer process. Low area-specific resistances with values ranging from 0.15 Ω cm² at 650 °C to 0.0086 Ω cm² at 800 °C were obtained. These results have demonstrated that the A-site cation-ordered perovskite oxide LBCO is a promising cathode material for IT-SOFCs.