Cathode Material For Intermediate Temperature Solid Oxide Fuel Cells Research Articles

Preparation and Properties of Fe-Based Double Perovskite Oxide as Cathode Material for Intermediate-Temperature Solid Oxide Fuel Cell.

Double perovskite oxides with mixed ionic and electronic conductors (MIECs) have been widely investigated as cathode materials for solid oxide fuel cells (SOFCs). Classical Fe-based double perovskites, due to their inherent low electronic and oxygen ionic conductivity, usually exhibit poor electrocatalytic activity. The existence of various valence states of B-site ions modifies the material's catalytic activity, indicating the possibility of the partial substitution of Fe by higher-valence ions. LaBaFe2-xMoxO5+δ (x = 0, 0.03, 0.05, 0.07, 0.1, LBFMx) is used as intermediate-temperature solid oxide fuel cell (IT-SOFC) cathode materials. At a doping concentration above 0.1, the Mo substitution enhanced the cell volume, and the lattice expansion caused the formation of the impurity phase, BaMoO4. Compared with the parent material, Mo doping can regulate the oxygen vacancy concentration and accelerate the oxygen reduction reaction process to improve the electrochemical performance, as well as having a suitable coefficient of thermal expansion and excellent electrode stability. LaBaFe1.9Mo0.1O5+δ is a promising cathode material for IT-SOFC, which shows an excellent electrochemical performance, with this being demonstrated by having the lowest polarization resistance value of 0.017 Ω·cm2 at 800 °C, and the peak power density (PPD) of anode-supported single-cell LBFM0.1|CGO|NiO+CGO reaching 599 mW·cm-2.

Characterization of A-site doped PrBaCo2O5+δ perovskites as cathode materials for IT-SOFCs

Creating highly efficient and durable cathodes persists as a formidable task in the realm of intermediate temperature solid oxide fuel cells (IT-SOFCs). Hence, we present a double perovskite oxide, Pr0.6Sr0.4BaCo2O5+δ (PS0.4BC), and its electrocatalytic activity is thoroughly investigated. The XRD test is carried out and a notable transformation in the phase structure is observed upon the introduction of Sr2+ ions into the PBC matrix. That is, the phase structure of the material changes from double perovskite structure to single perovskite structure. Through the TG and TEC test that the introduction of Sr2+ ions into the lattice can create additional sites for oxygen vacancy formation and reduce TEC values. Further verify that Sr doping can enhance the concentration of oxygen vacancies of the material. The PS0.4BC cathode material exhibits remarkably low polarization resistance, achieving an impressive value of 0.027 Ω cm2 at an operating temperature of 800 °C. Oxygen partial pressure test shows that as the oxygen partial pressure decreases, there is a notable increase in impedance, particularly evident in the low frequency region of the Nyquist plots. This indicates that the oxygen content has obvious effects on the low-frequency processes. When the oxygen partial pressure exceeds 0.05 atm, the oxygen adsorption-dissociation and diffusion process is the rate-limiting step in the ORR. However, when the oxygen partial pressure is less than 0.05 atm, the formation of lattice oxygen through the combination of oxygen ions and oxygen vacancies processes is the rate-limiting step. Compared PBC cathode material, the more pronounced changes in the high frequency arc of the PS0.4BC cathode at the same oxygen content. It shows that Sr doping significantly changes the high frequency process. After doping, the oxygen vacancy concentration increases, which facilitates the occurrence of the charge transfer process at high frequency.

Structural and Electrochemical Characterisation of NBZFO Cobalt-Free Cathode Material for Intermediate-Temperature Solid Oxide Fuel Cells: An Experimental Investigation

Compared to other energy-generating technologies and energy conversion devices, intermediate-temperature solid oxide fuel cells (IT-SOFCs) have gained significant attention from energy experts due to its high energy density, moderate operating temperature (600–800°C), low emissions and reliability. Enhancing the performance of IT-SOFCs requires suitable and excellent cathode materials. Thus, a perovskite-type Nd0.5Ba0.5Zr0.8Fe0.2O3+δ (NBZFO) material was synthesised via traditional solid-state reaction technique and analysed as a potential cathode material for IT-SOFCs. Analysis of X-ray diffraction data (XRD) revealed a single-phase perovskite material that crystallises in cubic space group (pm-3m). The thermal and electrochemical properties were analysed with the aid of thermogravimetric analysis (TGA) and electrochemical impedance spectroscopy (EIS). NBZFO has an electrical conductivity in air of 80 S cm−1 at 400°C and a polarisation resistance (Rp) of 0.106 Ω cm2 at 800°C. TGA reveals a slight loss in weight of about 0.58%, thereby suggesting a highly stable cathode material for IT-SOFC. Electrochemical investigation shows that NBZFO has good electronic and ionic conductivity and excellent oxygen stichometry. Further studies are required to understand the effects of varying B-site composition of the cathode material.

CO2-tolerant and cobalt-free La4Ni3-xCuxO10±δ (x = 0, 0.3, 0.5 and 0.7) cathodes for intermediate-temperature solid oxide fuel cells

Cu is doped to La4Ni3O10±δ to improve its electrochemical performance as a potential intermediate-temperature solid oxide fuel cell (IT-SOFC) cathode material. A new higher-order Ruddlesden-Popper (R-P) phase composition La4Ni3-xCuxO10±δ, (L4N3-xCx, 0.0 ≤ x ≤ 0.7) is synthesized using an EDTA-citrate process. The L4N3-xCx cathode has a good chemical compatibility with the La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) electrolyte. A thermodynamic stability test shows that L4N3-xCx is stable after 72 h exposure to 600, 700, and 800 °C in air. The L4N3-xCx cathode shows chemical stability against CO2, and a stable structure over 12 h in CO2 has been demonstrated. The thermal expansion coefficients (TECs) have been determined to be in the range of 14.1–14.6 × 10−6 K−1, close to that of the LSGM electrolyte. The Cu content (x) significantly affects the electrical conductivity and sinter density of L4N3-xCx. La4Ni2.7Cu0.3O10 (L4N2.7C0.3) displays the highest electrical conductivity value of which reaches about 383 to 319 S cm−1 at 600–800 °C. In addition, Cu doping improves the electrochemical performance of L4N3-xCx. The area specific resistance (ASR) of the La4Ni2.5Cu0.5O10 (L4N2.5C0.5) cathode was found to be 0.045 Ω cm2 at 800 °C, which is significantly better than that of L4N3. The peak power density of a single cell using the L4N2.5C0.5 cathode is 526 mW cm−2 at 800 °C, and a 200 h long-term test demonstrates good stability. These results indicate that La4Ni3-xCuxO10±δ cathode is a promising cathode material for IT-SOFCs.

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

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

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

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

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

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

Performance evaluation of Ca2.9−xBi0.1PrxCo4O9−δ cathode for anode-supported intermediate temperature solid oxide fuel cells

The Ca2.9−xBi0.1PrxCo4O9−δ (CBPxC, x = 0–0.6) oxides were prepared by sol–gel method, as the potential cathode of anode-supported intermediate temperature solid oxide fuel cells (IT-SOFCs). The electrochemical performance test showed that the CBPxC oxide sintered at 700 °C for 10 h could form a single-phase crystal structure, and when the doping ratio of Pr ion was x = 0.4, the CBPxC cathode on the SDC electrolyte sintered at 950 °C for 5 h obtained the minimum interface polarization resistance (about 0.406 Ω·cm2 at 800 °C). Meanwhile, on the basis of the above conditions, we had fabricated Ni0.95Cu0.05Ox-SDC/SDC/CBP0.4C single cell with the optimized CBPxC (x = 0.4) cathode, in which the SDC electrolyte thickness was 55.6 μm. The maximum power densities of the single cell reached 0.705 W/cm2 and 0.570 W/cm2 at 800 °C and 750 °C, the corresponding polarization resistances were 0.051 Ω·cm2 and 0.153 Ω·cm2, respectively. This suggested that CBP0.4C was a very promising cathode material for IT-SOFCs.

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

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

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.

Co-doped cerium oxide Fe0.25-xMnxCe0.75O2-δ as a composite cathode material for IT-SOFC

In this study, Fe-Mn co-doped ceria Fe0.25Mn0.00Ce0.75O2-δ (FMDC1), Fe0.23Mn0.02Ce0.75O2-δ (FMDC2), Fe0.21Mn0.04Ce0.75O2-δ (FMDC3), and Fe0.19Mn0.06Ce0.75O2-δ (FMDC4) powders are synthesized by sol gel method and evaluated as cathode materials for intermediate temperature solid oxide fuel cell (IT-SOFC). The combination of Fe and Mn significantly enhanced the ceria catalytic activity and oxygen kinetics for redox-based reactions. The effects of the co-doping mechanism on the phase composition, optical behavior, and electrochemical performance are mainly investigated. The prepared samples are characterized by XRD, SEM, FTIR, UV–vis, and conductivity tests. X-ray diffraction analysis revealed well-developed crystallinity with a single phase cubic structure of synthesized cathode material. SEM depicted the highly porous facet for Fe0.19Mn0.06Ce0.75O2-δ (FMDC4) resulted in the large triple-phase boundaries for the reduction of ambient air. The inclusion of Mn3+and Fe3+ ions into CeO2 network created additional oxygen vacancies (Ov) and simultaneously reduced the optical band gap energy from 2.81 eV for FMDC1 (x = 0.00) to 2.54 eV for FMDC4 (x = 0.06). Among the four samples, FMDC4 possessed the highest electrical conductivity (∼0.89 Scm−1) at 650 °C and corresponding low activation energy of ∼0.301 eV, which lead to good catalytic activity with an enhanced electrochemical performance of the SOFC system. The open-circuit voltage (OCV) attained the value of ∼0.98 V, maximum power density of ∼335 mW cm−2 is obtained at 550 °C, which is comparable to previously reported electrodes. The results suggested that the combination of Fe and Mn into ceria can be used as an effective catalytic promoter for oxygen reduction reactions (ORR), and the composition of FMDC4 resulted in the peak conductivity, short term stability and highest power density as compared to other synthesized samples.

Electrode properties of CuBi2O4 spinel oxide as a new and potential cathode material for solid oxide fuel cells

Herein, the spinel oxide CuBi 2 O 4 is prepared by solid-state reaction method and characterized for the first time as a cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). CuBi 2 O 4 (CBO) crystallizes in tetragonal structure and is chemically compatible with Ce 0.9 Gd 0.1 O 1.9 (GDC) electrolyte at 800 °C. Electrical conductivity relaxation is conducted to assess the oxygen surface exchange coefficient k chem and oxygen bulk diffusion coefficient D chem of CBO material. It is found that CBO exhibits better oxygen transport properties than the traditional La 0.8 Sr 0.2 MnO 3 (LSM) and La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) cathodes. The electrochemical activity of CBO-based cathode is investigated by impedance spectroscopy on the symmetric cell with GDC electrolyte. The CBO cathode forms good contact with the GDC electrolyte and displays low polarization resistance ( R P ) values, e.g., 0.58 Ωcm 2 at 700 °C in air. The introducing GDC to form a composite cathode with CBO further reduces the R P to 0.39 Ωcm 2 . An anode-supported single cell with the CBO-GDC cathode exhibits a peak power density of 507 mWcm −2 at 750 °C, suggesting the viability of CBO oxide as a cathode material for IT-SOFC. • CuBi2O4 exhibits fast surface oxygen exchange and bulk diffusion properties. • CuBi2O4 forms good contact with GDC electrolyte at low sintering temperatures. • CuBi2O4 cathode shows improved electrochemical performance below 700 °C.

CO2-tolerant Sr2CoTaO6-δ double perovskite oxide as a novel cathode for intermediate-temperature solid oxide fuel cell

Sr2CoTaO6-δ (SCT) double perovskite oxide was synthesized as potential cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). We systematically characterize its phase structure, thermal stability, thermal expansion, electrical conductivity, and electrochemical performance. The SCT exhibits superior phase stability and high CO2-tolerant properties at high temperatures. The electrical conductivity of SCT is semiconductor-like and achieves its maximum value of 7 S cm-1 at 800 °C. The average thermal expansion coefficient of SCT in air is 15.0 × 10–6 K-1 in a temperature range of 30–1000 °C. The area specific resistance of SCT cathode on Gd0.1Ce0.9O1.95 (GDC) electrolyte is 0.029 Ω cm2 at 800 °C. An electrolyte-supported single cell with a thick-film GDC electrolyte (300 µm) reaches a maximum peak power density of 448 mW/cm2 at 800 °C. With high phase stability and superior electrocatalytic activity indicate that SCT is a potential novel cathode material for IT-SOFCs.

Effect of calcium doping on Sm1–xCaxBaCo2O5+δ cathode materials for intermediate-temperature solid oxide fuel cells

Here, Sm1–xCaxBaCo2O5+δ (x = 0–0.4; SCBC) oxygen-deficient perovskites were synthesized by a sol–gel method and studied as potential novel cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs). As an effective doping strategy, partial substitution of Ca for Sm in SmBaCo2O5+δ could reduce the thermal expansion coefficient (TEC) and improve the conductivity and catalytic activity of the oxygen reduction reaction (ORR). The x = 0–0.2 samples obtained after sintering at 1100 °C crystallized in an orthorhombic structure with the space group Pmmm and had good chemical compatibility with CeO2-based electrolytes at 1000 °C for 10 h. The TECs of the SCBC samples decreased from 20.2 × 10−6 K−1 (x = 0) to 17.7 × 10−6 K−1 (x = 0.2). The area-specific resistances (ASRs) of the x = 0–0.4 cathodes were 0.163, 0.114, 0.075, and 0.090 Ω cm2 at 700 °C. Additionally, the x = 0.2 cathode showed good electrochemical stability in a CO2-containing atmosphere. All results clearly indicated that double perovskite SCBC (x = 0–0.3) are promising cathode materials for IT-SOFCs.

Improved thermal expansion and electrochemical performance of La1−xSrxFe0.7Ni0.3O3−δ cathodes for intermediate-temperature SOFCs

Perovskite oxides of composition La1−xSrxFe0.7Ni0.3O3−δ (LSFN-x, 0 ≤ x ≤ 0.4) were evaluated as candidate cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Their crystal structures, electrical conductivity, thermal expansion coefficient (TEC), and electrochemical performance were investigated as a function of their Sr content. An orthorhombic structure was obtained when 0.3 equivalents of Ni were substituted at the Fe sites, resulting in LaFe0.7Ni0.3O3−δ, and the crystal structure was transformed from orthorhombic to hexagonal upon the substitution of Sr at La sites. Sr doping was found to increase the TEC of the LSFN material, resulting in a good thermal match with the commonly used Gd0.1Ce0.9O2−δ (GDC) electrolyte. The LSFN-0.2 also exhibited good chemical compatibility with the GDC electrolyte at temperatures <1000 °C. A gradual increase in electrical conductivity with increasing Sr content was observed because of the increase in the concentration of electronic defects. The cathode electrochemical performance was investigated by AC impedance spectroscopy. Among the LSFN series, LSFN-0.2 exhibited the lowest polarization resistance value of 0.065 Ω cm2 at 800 °C. The substitution of Sr can promote charge transfer and the adsorption/dissociation of oxygen molecules, thereby decreasing the polarization resistance of the LSFN material. X-ray photoelectron spectroscopy measurements were conducted to elucidate the cause of the performance improvement. The results indicated that the LSFN-0.2 material has potential applications as cathode material for IT-SOFCs.

Synergistic electron doping and ion conductive phase incorporating of SrCoO3-δ as desirable cathode materials for intermediate-temperature solid oxide fuel cells

Mixed conducting perovskite-structured oxides are desirable catalysts toward the oxygen reduction reaction (ORR) process. Pure cubic perovskite-structured SrCoO3–δ is a promising class of mixed conductors with high ORR activity. However, it suffers from structural instability and thermal incompatibility at elevated temperatures, thereby impeding its practical application in intermediate-temperature solid oxide fuel cells (IT-SOFCs). In this work, A-site electron doping in SrCoO3–δ was conducted to chemically compensate for the loss of lattice oxygen, thus improving the structural stability of SrCoO3–δ. Among the as-prepared Y-doped Sr1−xYxCoO3−δ (x = 0.05–0.20) samples, 10 mol% Y-doping of Sr0·9Y0·1CoO3–δ (SYC10) experimentally exhibits desirable electrical conductivity and lowest area specific resistance (ASR) while maintaining structural stability at elevated temperatures. The results are confirmed by first-principles calculations that involve density of states and oxygen vacancy formation energy. In addition, Gd0.1Ce0·9O1.95 incorporation further improves the thermal compatibility and cell performance, where the measured thermal expansion coefficients between 30 °C and 1000 °C decrease from 23.3 × 10−6 K−1 for SYC10 to 19.0 × 10−6 K−1 for SYC10–40GDC, and the corresponding ASRs with La0·9Sr0.1Ga0.8Mg0·2O3–δ electrolyte decrease from 0.080 Ω cm2 to 0.044 Ω cm2 at 700 °C. Results suggest that SYC10–40GDC is a desirable cathode material for IT-SOFCs.

Optimization electrochemical performance and thermal compatibility via SmBa0.5Sr0.5CoCuO5+δ and Ce0.9Gd0.1O1.95 composite cathodes for intermediate-temperature solid oxide fuel cells

The SmBa0.5Sr0.5CoCuO5+δ- $$x$$ Ce0.9Gd0.1O1.95 ( $${\text{SBSCCo}}-x{\text{GDC}}$$ , $$x$$ = 20–50 wt%) composite cathodes are prepared by physical mixture. Its properties are investigated as cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The X-ray diffraction (XRD) spectra show that there are no chemical reaction between SBSCCo cathode and GDC electrolyte after co-sintered at 950 °C for 10 h and 800 °C for 100 h, respectively. With the increase of GDC weight ratio, the thermal expansion coefficient (TEC) of $${\text{SBSCCo}}-x{\text{GDC}}$$ composite cathodes is obviously reduced. The TEC of SBSCCo-50GDC is reduced to $$13.14 \times 10^{ - 6} {\text{ k}}^{{ - 1}}$$ from 30 to 850 °C. The conductivity of $${\text{SBSCCo}}-x{\text{GDC}}$$ composite cathodes shows the characteristic of transition from semiconductor to metal with increased temperature. The addition of GDC into SBSCCo cathode significantly improves the catalytic activity of $${\text{SBSCCo}}-x{\text{GDC}}$$ composite cathodes. The polarization resistance of SBSCCo-30GDC composite cathode on GDC electrolyte reaches 0.022 $$\Omega {\text{cm}}^{2}$$ at 800 °C in air. During the stability test, the polarization resistance of SBSCCo-30GDC composite cathode increased by 9.8% in 80 h. The maximum power density of fuel cell with SBSCCo-30GDC composite cathode on 0.3-mm-thick GDC electrolyte reaches 662 mW cm−2 at 800 °C. These primarily results suggest that $${\text{SBSCCo}}-30{\text{GDC}}$$ composite cathode is a promising cathode material for IT-SOFCs.

Electrochemical properties of La1.5Pr0.5Ni0.95−xCuxAl0.05O4+δ Ruddlesden-Popper phase as cathodes for intermediate-temperature solid oxide fuel cells

The Ruddlesden-Popper materials La1.5Pr0.5Ni0.95−xCuxAl0.05O4+δ (x = 0, 0.1, 0.25, 0.5, 0.75, 0.95), La1.5Pr0.5NiO4+δ, and La1.5Pr0.5CuO4+δ have been synthesized by the sol-gel method as cathode materials on the SDC (Sm0.2Ce0.8O1.9) electrolyte for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The cathode materials sintered at 700 and 800 °C for 72 h, also showing good phase stability. The maximum conductivity of this series reached approximately 50 S cm−1 at 350 °C with x = 0.25. The lowest area-specific resistance (ASR) of the cathode measured on the SDC was 0.04 Ω cm2 at 800 °C with x = 0.1. The maximum power density of the SDC-supported single-cell reached 530 mW cm−2 at 800 °C with x = 0.1. Among all of the samples, La1.5Pr0.5Ni0.85Cu0.1Al0.05O4+δ exhibited excellent electrochemical performance, making it a promising candidate cathode material for IT-SOFCs.

Cathode Performance Study of La0.6Sr0.4Co0.8Fe0.2O3-δ with Various Electrolyte-Doped Ceria Ce0.8Sm0.17Ln0.03O1.9 for IT-Solid Oxide Fuel Cell

La0.6Sr0.4Co0.8Fe0.2O3-δ (LSCF) cathode perovskite prepared by a Pechini method deposited on ceria co-doping Ce0.8Sm0.17Ln0.03O1.9 (LnSDC), with (Ln = La, Y, and Nd) electrolytes was successfully prepared by the solid-state reaction method. In this preparation process, thick and thin films of LSCF were deposited upon dense Ln-doped ceria LnSDC electrolytes after 5 and 3 spin-coating and dip-coating cycles, respectively. Two layers of LSCF were deposited by screen-printing in order to obtain thick cathode films. After deposition, some structural and morphologic characterizations, such as X-ray diffraction analysis and scanning electron microscopy, have been conducted to understand the properties of the elaborated samples and to study the impact of doping on these properties. Electrochemical impedance spectroscopy measurements on symmetric cells were also performed to investigate the employability of L0.6Sr0.4Co0.8Fe0.2O3-δ as a cathode material deposited upon LnSDC electrolytes for intermediate-temperature solid oxide fuel cells (IT-SOFC). According to what was available and inferred after studying the images from a scanning electron microscope, no cracks or significant segregation were detected in the LSCF/LnSDC interface. This behavior is consistent with the good thermal expansion compatibility between the two materials. Electrochemical impedance spectroscopy investigations at 700°C, indicate relatively low area-specific resistance between 0.048 and 0.1 Ω cm2 for all symmetrical cell LSCF/doped electrolyte/LSCF. All the cells were previously sintered above 1400°C, in air. All these results showed that L0.6Sr0.4Co0.8Fe0.2O3- δ can stand as a potential candidate for new cathode material in IT-SOFCs.