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 Pr_0.2Sr_1.8CoTiO_6?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.     

Highly CO2RR activity and electrochemical performance of A-site deficient symmetrical electrode materials (La0.6Sr0.4)1−xFe0.8Ni0.2O3-δ for CO2 electrolysis

A-site deficient (La_0.6Sr_0.4)_1−xFe_0.8Ni_0.2O_3-δ (x = 0, 0.05, 0.1) perovskite oxide materials (LSFN100, LSFN95, and LSFN90) are evaluated as symmetrical electrode materials for CO₂ electrolysis. All three perovskite oxides display pure cubic perovskite structure. The introduction of A-site deficiency results in greater tendency of in-situ exsolution and stronger CO₂ adsorption capacity, which are verified by temperature-programmed reduction of H₂ and temperature-programmed desorption of CO₂. Furthermore, the current densities with LSNF90 symmetrical cell are 1.72, 1.18 and 0.72 A·cm⁻² under the applied voltage of 1.8 V at 850, 800 and 750 °C to electrolysis CO₂, respectively. Low polarization resistance of 0.186, 0.267 and 0.454 Ω·cm² is also observed under open circuit conditions at 850, 800 and 750 °C, respectively. A-site deficiency of perovskite materials reduces the activation energy of oxygen evolution reaction (OER) and carbon dioxide reduction reaction (CO₂RR). Symmetrical cell with LSFN90 electrode shows good electrochemical performance and long-term stability for CO₂ electrolysis.     

Comparative study on the electrochemical performance of Sr(Ti0.3Fe0.7)O3-δ fuel electrode in different fuel gases for solid oxide electrochemical cells

Sr(Ti_1-xFe_x)O_3?δ (STF) perovskite has been developed as one of the alternatives to Nickel-base fuel electrodes for solid oxide electrochemical cells (SOCs) that can provide good tolerance to redox cycling and fuel impurities. Recent results on STF fuel electrodes present excellent electrochemical performance and outstand stability both under H₂ fuel cell mode and H₂O electrolysis mode, however, the electrochemical characteristics in other fuel gases, such as CO, CO–H₂ mixture, CH₄, and CO–CO₂ mixture have not been investigated. Herein, we report the electrochemical performance of Sr(Ti_0.3Fe_0.7)O_3?δ fuel electrode on La_0.8Sr_0.2MnO_3?δ-Zr_0.92Y_0.16O_2?δ (LSM-YSZ) oxygen electrode supported SOCs with thin YSZ electrolyte using different fuel gases. At 800 °C, the peak power density slightly decreased from 0.9 W/cm² in wet H₂ to 0.68 W/cm² in wet CO under fuel cell mode. However, the cell only showed a peak power density of 0.27 W/cm² at 800 °C in wet CH₄, reaching 0.75 W/cm² at 850 °C, when the open-circuit voltage increased from 0.9 V to 1.02 V. STF fuel electrode exhibited much worse CO₂ electrolysis performance than steam electrolysis, especially in high CO₂ concentration due to the increased ohmic resistance and electrode polarization resistance.     

A medium-entropy perovskite oxide La0.7Sr0.3Co0.25Fe0.25Ni0.25Mn0.25O3-δ as intermediate temperature solid oxide fuel cells cathode material

In this study, we report a novel medium-entropy perovskite oxide of La_0.7Sr_0.3Co_0.25Fe_0.25Ni_0.25Mn_0.25O_3-δ (LSCFNM73) with high constitutive entropy (S_config) as the cathode material of intermediate temperature solid oxide fuel cells (IT-SOFCs). The intrinsic properties of phase structure, electrical conductivity, thermal expansion and oxygen adsorption capacity of La_1-xSr_xCo_0.25Fe_0.25Ni_0.25Mn_0.25O_3-δ (LSCFNM, x = 0, 0.1, 0.2, 0.3) oxides are evaluated in detail. The LSCFNM73 oxide exhibits the maximum electrical conductivity of 464 S cm⁻¹ at 800 °C and a relatively lower thermal expansion coefficient (TEC) of 15.34 × 10⁻⁶ K⁻¹, which is selected as the propriate cathode composition. The B-site of LSCFNM73 contains four elements which can increase the configuration entropy. Additionally, NiO-Yttria stabilized zirconia (YSZ) supported fuel cell is fabricated by tape casting, hot pressing-lamination, co-sintering and screen printing technologies. The fuel cell demonstrates a maximum power density of 1088 mW cm² at 800 °C, and excellent stability at 750 °C under 0.75V in 120 h and 10 times thermal cycling between 750 °C and 400 °C. Therefore, the medium-entropy LSCFNM73 oxide can be applied in IT-SOFCs as a competitive cathode material.     

Highly active and stable BaCo0.8Zr0.1Y0.1O3-δ cathode for intermediate temperature solid oxide fuel cells

Developing cathode material with high performance and excellent stability is the ultimate goal for solid oxide fuel cells (SOFCs). Based on this consideration, we design a new simple perovskite oxide BaCo_0.8Zr_0.1Y_0.1O_3-δ (BCZY) as the cathode material of SOFC without any further modification, which has good oxygen reduction reaction (ORR) activity and excellent stability in air and CO₂ at an intermediate temperature range of 600 ℃? 800 ℃. The area specific resistance (ASR) of symmetrical cell with BCZY cathode is 0.041 Ω cm² at 700 ℃, moreover, BCZY cathode keeps good structural and catalytic stability during 100 h test in air. The electrolyte-supported single cell fabricated with BCZY as cathode delivers a maximum power density of 460 mW cm^?2 and a superior steady operation over 200 h at 700 ℃. The good thermal physical structure stability of BCZY is further demonstrated by in-situ X-ray diffraction (XRD), good ORR activity and excellent CO₂ tolerance are further confirmed by density functional theory (DFT) calculations. These results indicates that BCZY maybe a potential cathode material for intermediate temperature SOFCs (IT-SOFCs).     

In-situ segregation of A-site defect (La0.6Sr0.4)0.90Co0.2Fe0.8O3-δ to form a high-performance solid oxide fuel cell cathode material with heterostructure

As a potential cathode material for solid oxide fuel cells, the commercial application of La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) has to face the challenges in insufficient oxygen reduction reaction (ORR) activity, segregation of Sr element, and CO₂ poisoning. Therefore, the effect of A-site non-stoichiometry on the electrochemical performance of (LS)_1-xCFs (x = ?0.05, 0, 0.05, 0.10, 0.15) from the aspect of microstructure/elemental surface chemical environment evolution is investigated in this paper. The results show that (LS)_0.90CF has the best ORR activity and the highest electrochemical performance. The excellent electrochemical performance is attributed to the (LS)_0.90CF/Co₂FeO₄/CoFe₂O₄-type heterostructure, formed by in-situ segregation induced by A-site defects, which improves the surface oxygen diffusion coefficient and chemical bulk diffusion coefficient of the cathode. At the same time, the A-site defect can effectively inhibit the segregation of Sr element in (LS)_0.90CF, thereby improving the tolerance of CO₂. At 800 °C, the area-specific resistance (ASR) of (LS)_0.90CF (0.023 Ω cm²) is 66.7% lower than that of LSCF (0.069 Ω cm²), and the peak power density (1.57 Wcm^?2) is 1.8 times higher than that of LSCF (0.87 Wcm^?2). Therefore, perovskite A-site defect-induced B-site segregation to form heterostructures provides an effective strategy for the preparation of high-performance cathode materials.     

Sr2Fe1.5Mo0.5O6–δ – Zr0.84Y0.16O2–δ Materials as Oxygen Electrodes for Solid Oxide Electrolysis Cells

The high‐temperature solid oxide electrolysis cell (SOEC) is one of the most promising devices for hydrogen mass production. To make SOEC suitable from an economical point of view, each component of the SOEC has to be optimized. At this level, the optimization of the oxygen electrode is of particular interest since it contributes to a large extent to the cell polarization resistance. The present paper is focused on an alternative oxygen electrode of Zr_0.84Y_0.16O_2–δ‐Sr₂Fe_1.5Mo_0.5O_6–δ (YSZ‐SFM). YSZ‐SFM composite oxygen electrodes were fabricated by impregnating the YSZ matrix with SFM, and the ion‐impregnated YSZ‐SFM composite oxygen electrodes showed excellent performance. For a voltage of 1.2 V, the electrolysis current was 223 mA cm⁻², 327 mA cm⁻² and 310 mA cm⁻² at 750 °C for the YSZ‐SFM10, YSZ‐SFM20, and YSZ‐SFM30 oxygen electrode, respectively. A hydrogen production rate as high as 11.46 NL h⁻¹ has been achieved for the SOEC with the YSZ‐SFM20 electrode at 750 °C. The results demonstrate that YSZ‐SFM fabricated by impregnating the YSZ matrix with SFM is a promising composite electrode for the SOEC.     

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 La_0.8Sr_0.2Fe_1-xCu_xO_3-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 La_0.8Sr_0.2Fe_0.8Cu_0.2O_3-δ (LSFCu2) fiber cathode displays the optimal electrochemical performance, and the polarization resistance (R_p) 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 (P_m) of the Ni-SDC/SDC/LSFCu2 single cell reaches 362 mW cm^-2 at 650 °C.     

Evaluation of Cu-substituted La1.5Sr0.5NiO4+δ as air electrode for CO2 electrolysis in solid oxide electrolysis cells

Ruddlesden-Popper oxide, Cu-substituted La_1.5Sr_0.5NiO_4+δ series materials (La_1.5Sr_0.5Ni_1-xCu_xO_4+δ; denoted as LSNCu_x; x = 0, 0.1, 0.25, 0.5) are investigated as air electrodes in solid oxide electrolysis cells (SOECs) for electrolysis of CO₂. Room temperature crystal structure, electrical conductivity and oxygen exchange capacity, as well as electrochemical performance of LSNCu_x are comprehensively investigated. Among the series of samples, LSNCu_0.25 half-cell exhibits the lowest polarization resistance value of 0.179 Ω cm² at 800 °C, which decreases by approximately 86.07% compared with that of LSN. In addition, the fuel electrode-supported single cell with LSNCu_0.25 air electrode presents a high current density of 1.2 A cm^?2 at 1.5 V under 30% CO–70% CO₂ condition at 800 °C, which is 207% of LSN (0.58 A cm^?2) under the same condition. Results show that the impressive catalytic activity for oxygen evolution reaction (OER) is ascribed to the improved electronic conductivity and oxygen exchange capacity. With Cu substitution for Ni-site, the contraction of Ni–O bond in NiO₆ octahedron and increased concentration of charge carries owing to the oxidation of Ni²⁺ to Ni³⁺ are beneficial to the electron conduction. The formation of more interstitial oxygen as ionic compensation also favors the oxygen ion diffusion/exchange and greatly accelerates the charge transfer process. Furthermore, no degradation is observed for the single cell durability test at 750 °C for 50 h, which demonstrates the highly stable performance of LSNCu_0.25 air electrode for electrolysis of CO₂.     

Microstructural analysis of highly active cathode material La0.7Sr0.3Ti0.15Fe0.65Ni0.2O3-δ (LSTFN) by optimizing different processing parameters

The modified Pechini method was applied to prepare a highly active and novel cathode material La_0.7Sr_0.3Ti_0.15Fe_0.65Ni_0.2O_3-δ (LSTFN). This material was coated on the LGSM electrolyte through a screen-printing technique with variable thicknesses of 28 ± 8, 41 ± 8, and 62 ± 8 μm, respectively. Different fabrication parameters, including sintering temperature, time, coating thickness, and variations in ball-milling, which affect the electrochemical performance of the cathode material, were investigated. X-ray diffraction analysis of the cathode material suggested that it exhibits a cubic crystal structure with a LSTFN single phase. The morphological studies were conducted using scanning electron microscopy (SEM), which confirmed that the electrode material had a highly porous structure. Meanwhile, the electrochemical properties of the material were studied by electrochemical impedance spectroscopy (EIS), which revealed that by varying different parameters, the electrochemical performance of the electrode material was enhanced. The coated cathode materials with variable thicknesses were analyzed at different sintering temperatures and times. Experimental results suggest that the optimum sintering temperature and time were 950 °C and 3 h, respectively, at which LSTFN exhibits the minimum polarization resistance (R_P) of 0.046 Ωcm² when sintered at 800 °C for 3 h.     

Tailoring the electrochemical reduction kinetics of dual-phase BaCe0.5Fe0.5O3-δ cathode via incorporating Mo for IT-SOFCs

The BaCe_0.5Fe_0.5O_3-δ (BCF) cathode consists of the ion-electron mixed conducting phase BaCe_0.15Fe_0.85O_3-δ (BCF1585) and the proton-conducting phase BaCe_0.85Fe_0.15O_3-δ (BCF8515). In this paper, the electrochemical performance is improved by incorporating the high valence element Mo into the BCF and applied to intermediate-temperature solid oxide fuel cells (IT-SOFCs). High-temperature X-ray diffraction (HT-XRD) and O₂-temperature programmed desorption (O₂-TPD) results show that Mo doping enhances the structural stability of BCF. The X-ray photoelectron spectroscopy (XPS) results suggest that the introduction of Mo increases the amount of adsorbed oxygen and thus the oxygen reduction reaction (ORR) catalytic activity. Compared to BCF, the polarization impedance of BaCe_0.5Fe_0.45Mo_0.05O_3-δ (BCFM) at 800 °C is 0.154 Ω·cm², a reduction of 22 %. Meanwhile, the BCFM output power at 800 °C is 778.01 mW·cm⁻², an improvement of 32.17 %, and maintains a stable current density after 250 h at 0.7 V. The results demonstrate that Mo doping is an effective strategy to enhance the electrochemical performance of BCF.     

High temperature water electrolysis using metal supported solid oxide electrolyser cells (SOEC)

Metal supported cells as developed according to the DLR SOFC concept by applying plasma deposition technologies were investigated for use as solid oxide electrolyser cells (SOEC) for high temperature steam electrolysis. Cells consisting of a porous ferritic steel support, a diffusion barrier layer, a Ni/YSZ hydrogen electrode, a YSZ electrolyte and a LSCF oxygen electrode were electrochemically characterised by means of i-V characteristics and electrochemical impedance spectroscopy measurements including a long-term test over 2000 h. The cell voltage during electrolysis operation at a current density of −1.0 A cm⁻² was 1.28 V at an operating temperature of 850 °C and 1.4 V at 800 °C. A long-term test run over 2000 h with a steam content of 43% at 800 °C and a current density of −0.3 A cm⁻² showed a degradation rate of 3.2% per 1000 h. The impedance spectra revealed a significantly enhanced polarisation resistance during electrolysis operation compared to fuel cell operation which was mainly attributed to the hydrogen electrode.     

Synthesis and Electrochemical Properties of BaFe1−xCuxO3−δ Perovskite Oxide for IT‐SOFC Cathode

A series of iron‐based perovskite oxides BaFe_1−xCu_xO_3−δ (x = 0.10, 0.15, 0.20 and 0.25, abbreviated as BFC‐10, BFC‐15, BFC‐20 and BFC‐25, respectively) as cathode materials have been prepared via a combined EDTA‐citrate complexing sol‐gel method. The effects of Cu contents on the crystal structure, chemical stability, electrical conductivity, thermal expansion coefficient (TEC) and electrochemical properties of BFC‐x materials have been studied. All the BFC‐x samples exhibit the cubic phase with a space group Pm3m (221). The electrical conductivity decreases with increasing Cu content. The maximum electrical conductivity is 60.9 ± 0.9 S cm⁻¹ for BFC‐20 at 600 °C. Substitution of Fe by Cu increases the thermal expansion coefficient. The average TEC increases from 20.6 × 10⁻⁶ K⁻¹ for BFC‐10 to 23.7 × 10⁻⁶ K⁻¹ for BFC‐25 at the temperature range of 30–850 °C. Among the samples, BFC‐20 shows the best electrochemical performance. The area specific resistance (ASR) of BFC‐20 on SDC electrolyte is 0.014 Ω cm² at 800 °C. The single fuel cell with the configguration of BFC‐20/SDC/NiO‐SDC delivers the highest power density of 0.57 W cm⁻² at 800 °C. The favorable electrochemical activities can be attributed to the cubic lattice structure and the high oxygen vacancy concentration caused by Cu doping.     

Preparation and Electrochemical Properties of Sr‐doped K2NiF4‐type Cathode Material Pr1.7Sr0.3CuO4 for IT‐SOFCs

A novel K₂NiF₄‐type oxide Pr_1.7Sr_0.3CuO₄ (PSCu) is studied to obtain its electrochemical properties as the cathode for intermediate‐temperature solid oxide fuel cells (IT‐SOFCs). The PSCu cathode powder and Ce_0.8Sm_0.2O_1.9 (SDC) electrolyte powder were synthesized by sol‐gel method and glycine‐nitrate method, respectively. The crystal structure of PSCu powder and PSCu‐SDC composite powder were identified with X‐ray diffraction (XRD). It is shown that PSCu belongs to tetragonal K₂NiF₄‐type and has good chemical compatibility with SDC. The thermal expansion coefficient (TEC) of PSCu is close to that of SDC. The conductivity of PSCu tested with four‐probe method exhibits a semiconductor‐pseudometal transformation at 400–450 °C, where the maximum conductivity of 103.6 S cm⁻¹ is obtained. The polarization test indicates the area specific resistance (ASR) of PSCu decreases with increasing temperature, reaching 0.11 Ω cm² at 800 °C. The activation energy of oxygen reduction reaction during 600–800 °C is 1.19 eV. The single fuel cell performance test reveals the open circuit voltage (OCV) and resistivity of PSCu reduce with increasing temperature, but the power density ascends with increasing temperature. The maximal power density is 243 mW cm⁻² at 800 °C, and the corresponding current density and OCV are 633 mA cm⁻² and 0.77 V, respectively.     

Performance and stability of Ruddlesden-Popper La2NiO4+δ oxygen electrodes under solid oxide electrolysis cell operation conditions

Ruddlesden-Popper La₂NiO_4+δ (LNO) oxygen electrodes were investigated under solid oxide electrolysis cell (SOEC) operation conditions. The electrochemical performance of LNO was measured in both solid oxide fuel cell (SOFC) and SOEC modes at 750 °C in air. The results suggest that LNO oxygen electrodes exhibit high electrochemical activity and the processes related to oxygen adsorption, dissociation and diffusion dominate the oxygen evolution reaction on the electrodes. Electrical conductivity relaxation (ECR) measurements imply that LNO shows better oxygen surface exchange performance than conventional LSM and LSCF electrodes, because of its special crystal structure with flexible non-stoichiometric oxygen. Significant performance degradation was observed during polarization at 500 mA cm⁻² and 750 °C in the SOEC mode for 48 h. XRD and XPS results confirmed that high-order Ruddlesden-Popper La₃Ni₂O₇ and La₄Ni₃O₁₀ phases have great contributions to the performance degradation of LNO oxygen electrodes related to anodic current polarization at 500 mA cm⁻² and 750 °C.     

Electrochemical characterization of BaCe0·7Zr0·1Y0·16Zn0·04O3-δ electrolyte synthesized by combustion spray pyrolysis

BaCe_0·7Zr_0·1Y_0·16Zn_0·04O_3-δ perovskite has been investigated due to its potential as an electrolyte in industrial steam electrolysis applications. The lowest area specific resistance (ASR) is achieved as 4.0 Ω cm² at 711 °C under 3% wet Ar atmosphere. The conductivity is calculated as 2.93 × 10^?2 S cm^?1 and kept stable for a ~70 h testing period. ASR increased at lower temperature (511 °C) under the same atmosphere and a new impedance arc (with 4.5 Ω cm² ASR and 2 × 10^?8 F equivalent capacitance) is formed, indicating second phase formation. No second phase formation is observed at the same temperature under dry 5% H₂ in Ar. The second phase formation/degradation of the electrolyte is attributed to Ba(OH)₂ and CeO₂ formations around 500 °C under wet atmospheres. At elevated temperatures, ~700 °C, BaCe_0·7Zr_0·1Y_0·16Zn_0·04O_3-δ exhibits both excellent protonic conductivity and stability which makes it a great candidate for both industrial fuel cells and steam electrolysers.     

Synthesis of LSM–YSZ–GDC dual composite SOFC cathodes for high-performance power-generation systems

This article investigates a method in further improvement of a (La_0.8,Sr_0.2)MnO₃ (LSM)-Yttria-stabilized zirconia (YSZ) dual composite cathode by adding material with high ionic conductivity such as gadolinia-doped ceria (GDC). A nano-porous composite cathode containing LSM, YSZ, and GDC was prepared by a two-step polymerizable complex (PC) method which minimizes the formation of YSZ–GDC solid solution. The structure of the resulting LSM/GDC–YSZ dual composite cathode was such that the LSM and GDC phases were present on the YSZ core particles without formation of the La₂Zr₂O₇, SrZrO₃, and GDC–YSZ solid solution. At 800 °C, the electrode polarization resistance of the LSM/GDC–YSZ dual composite cathode decreased to 0.266 Ω cm², compared with 0.385 Ω cm² for the LSM/YSZ–YSZ dual composite cathode. In addition, the Ni–YSZ anode-supported single cell using a LSM/GDC–YSZ dual composite cathode with H₂ as the fuel achieved a maximum power density of 0.65 W cm⁻² at 800 °C.     

Effect of Fe doping on the performance of suspension plasma-sprayed PrBa0.5Sr0.5Co2−xFexO5+δ cathodes for intermediate-temperature solid oxide fuel cells

PrBa_0.5Sr_0.5Co_2–xFe_xO_5+δ (PBSCF) (X = 0, 0.3, 0.4, and 0.5) is investigated as cathode material for intermediate-temperature solid oxide fuel cells. Suspension plasma spraying is used as a low cost and large-scale manufacturing process to prepare PBSCF cathodes. Fe substitution effects on the crystal structure and electrochemical performance are characterized. All plasma-sprayed PBSCF cathodes exhibit a pure and stable cubic structure. The suspension plasma-sprayed PBSCF deposits show a porous and fine structure, and the microstructures are insensitive to Fe substitution. Subsequent to Fe doping, the polarization resistance of PBSCF cathodes rapidly decreases for increasing Fe substitution concentration from 0 to 0.4. Further increase of the Fe doping concentration increases the cathode polarization instead. At 600 and 700 °C, a 20% Fe-doped (x = 0.4) PBSCF cathode exhibits remarkably low area-specific polarization resistances (R_p) of 0.074 Ω cm² and 0.012 Ω cm², respectively. Moreover, the R_p of all cathodes remains almost identical after isothermal annealing at 600 °C for 300 h. Furthermore, the thermally-sprayed porous metal-supported cell assembled with the optimal PBSCF cathode shows excellent performance with peak power densities of 0.37, 0.8, and 1.35 W cm⁻² at 500, 600, and 700 °C, respectively.     

A novel BaCe0.5Fe0.3Bi0.2O3–δ perovskite-type cathode for proton-conducting solid oxide fuel cells

A perovskite-type BaCe_0.5Fe_0.3Bi_0.2O_3-δ (BCFB) was employed as a novel cathode material for proton-conducting solid oxide fuel cells (SOFCs). The single cells with the structure of NiO-BaZr_0.1Ce_0.7Y_0.2O_3-δ (BZCY7) anode substrate|NiO-BZCY7 anode functional layer|BZCY7 electrolyte membrane|BCFB cathode layer were fabricated by a dry-pressing method and investigated from 550 to 700 °C with humidified hydrogen (~3% H₂O) as the fuel and the static air as the oxidant. The low interfacial polarization resistance of 0.098 Ω cm² and the maximum power density of 736 mW cm⁻² are achieved at 700 °C. The excellent electrochemical performance indicates that BCFB may be a promising cathode material for proton-conducting SOFCs.     

Electrochemical performance of intermediate temperature micro-tubular solid oxide fuel cells using porous ceria barrier layers

We describe the manufacture and electrochemical characterization of micro-tubular anode supported solid oxide fuel cells (mT-SOFC) operating at intermediate temperatures (IT) using porous gadolinium-doped ceria (GDC: Ce_0.9Gd_0.1O_2−δ) barrier layers. Rheological studies were performed to determine the deposition conditions by dip coating of the GDC and cathode layers. Two cell configurations (anode/electrolyte/barrier layer/cathode): single-layer cathode (Ni–YSZ/YSZ/GDC/LSCF) and double-layer cathode (Ni–YSZ/YSZ/GDC/LSCF–GDC/LSCF) were fabricated (YSZ: Zr_0.92Y_0.16O_2.08; LSCF: La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ). Effect of sintering conditions and microstructure features for the GDC layer and cathode layer in cell performance was studied. Current density–voltage (j–V) curves and impedance spectroscopy measurements were performed between 650–800 °C, using wet H₂ as fuel and air as oxidant. The double-cathode cells using a GDC layer sintered at 1400 °C with porosity about 50% and pores and grain sizes about 1 μm, showed the best electrochemical response, achieving maximum power densities of up to 160 mW cm⁻² at 650 °C and about 700 mW cm⁻² at 800 °C. In this case GDC electrical bridges between cathode and electrolyte are preserved free of insulating phases. A preliminary test under operation at 800 °C shows no degradation at least during the first 100 h. These results demonstrated that these cells could compete with standard IT-SOFC, and the presented fabrication method is applicable for industrial-scale.