Fabrication and characterization of anode-supported single chamber solid oxide fuel cell based on La0.6Sr0.4Co0.2Fe0.8O3−δ–Ce0.9Gd0.1O1.95 composite cathode

Anode-supported solid oxide fuel cells consisting of nickel–gadolinium doped ceria (NiO–CGO, 60:40 wt%) anode, gadolinium doped ceria (CGO) electrolyte and lanthanum strontium cobaltite ferrite–gadolinium doped ceria (LSCF–CGO) cathode are developed and operated under single-chamber conditions, utilizing methane/air mixture. The cell performance is optimized regarding the electrolyte microstructure, cathode composition and testing conditions. The performance of the cell improves with the decrease of the thickness of the electrolyte and the increase of the ratio of methane to oxygen. The test cell with LSCF–CGO cathode (70:30 wt%) that was sintered at 1100 °C for 2 h and 150 μm dense electrolyte exhibits the maximum power output of ∼260 mW cm⁻² at 600 °C in CH₄/O₂ = 2 atmosphere.     

Study of oxygen reduction mechanism on Ag modified Sm1.8Ce0.2CuO4 cathode for solid oxide fuel cell

Different amount of metal silver particles are infiltrated into porous Sm_1.8Ce_0.2CuO₄ (SCC) scaffold to form SCC–Ag composite cathodes. The chemical stability, microstructure evolution and electrochemical performance of the composite cathode are investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and AC impedance spectroscopy respectively. The composite cathode exhibits enhanced chemical stability. The metal Ag remains un-reacted with SCC and Ce_0.9Gd_0.1O_1.95 (CGO) at 800 °C for 72 h. The polarization resistance of the composite cathode decreases with the addition of metal Ag. The optimum cathode SCC-Ag05 exhibits the lowest area specific resistance (ASR, 0.43 Ω cm²) at 700 °C in air. Investigation shows that metal Ag accelerates the charge transfer process in the composite cathode, and the rate limiting step for electrochemical oxygen reduction reaction (ORR) changes to oxygen dissociation and diffusion process.     

Superior electrochemical performance and oxygen reduction kinetics of layered perovskite PrBaxCo2O5+δ (x = 0.90–1.0) oxides as cathode materials for intermediate-temperature solid oxide fuel cells

The layered perovskite PrBa_xCo₂O_5+δ (PB_xCO, x = 0.90–1.0) oxides have been synthesized by a solid-state reaction technique, and evaluated as the potential cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Room temperature X-ray diffraction patterns show the orthorhombic structures which double the lattice parameters from the perovskite cell parameter as a ≈ a_p, b ≈ a_p and c ≈ 2a_p (a_p is the cell parameter of the primitive perovskite) in the Pmmm space group. There is a good chemical compatibility between the PB_xCO cathode and the Ce_0.9Gd_0.1O_1.95 (CGO) electrolyte at 1000 °C. The electrical conductivity and thermal expansion coefficient of PB_xCO are improved due to the increased amount of electronic holes originated from the Ba-deficiency. The results demonstrate the high electrochemical performance of PB_xCO cathodes, as evidenced by the super low polarization resistances (R_p) over the intermediate temperature range. The lowest R_p value, 0.042 Ω cm², and the cathodic overpotential, −15 mV at a current density of −25 mA cm⁻², are obtained in the PrBa_0.94Co₂O_5+δ cathode at 600 °C in air, which thus allow to be used as a highly promising cathode for IT-SOFCs. A CGO electrolyte fuel cell with the PrBa_0.94Co₂O_5+δ cathode presents the attractive peak power density of ∼1.0 W cm⁻² at 700 °C. Furthermore, the oxygen reduction kinetics of the PrBa_0.94Co₂O_5+δ cathode is also studied, and the rate-limiting steps for oxygen reduction reaction are determined at different temperatures.     

Evaluation and optimization of Bi1−xSrxFeO3−δ perovskites as cathodes of solid oxide fuel cells

Lattice expansion behaviour, oxygen nonstoichiometry, mean iron oxidation state, electrical conductivity and interfacial polarization resistance of Bi_1−xSr_xFeO_3−δ were reported as a function of Sr-doping content for x = 0.3, 0.5 and 0.8. Among the series, Bi_0.5Sr_0.5FeO_3−δ (BSF5) demonstrates the optimum performance in terms of the lowest interfacial polarization resistance and the largest oxygen nonstoichiometry. It is demonstrated that the best microstructure and the lowest interfacial resistance can be obtained by firing BSF5 onto dense Sm_0.2Ce_0.8O_1.9 (SDC) electrolyte at 1000 °C. BSF5 exhibits good chemical compatibility with SDC; however, firing temperature above 1000 °C results in the formation of bismuth-deficient perovskite with inferior activity for oxygen reduction reaction. We also show that single-phase BSF5 cathode provides better electrode performance than its composite with SDC. This is due to the increased charge-transfer resistance upon adding SDC which have negligible electronic conductivity.     

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.     

Electrochemical performance of La2Cu1−xCoxO4 cathode materials for intermediate-temperature SOFCs

K₂NiF₄-type structure oxides La₂Cu_1−xCo_xO₄ (x = 0.1, 0.2, 0.3) are synthesized and evaluated as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). The materials are characterized by XRD, SEM and electrochemical impedance spectrum (EIS), respectively. The results show that no reaction occurs between La₂Cu_1−xCo_xO₄ electrode and Ce_0.9Gd_0.1O_1.95 (CGO) electrolyte at 1000 °C. The electrode forms good contact with the electrolyte after sintering at 800 °C for 4 h in air. The electrode properties of La₂Cu_1−xCo_xO₄ are studied under various temperatures and oxygen partial pressures. The optimum composition of La₂Cu_0.8Co_0.2O₄ results in 0.51 Ω cm² polarization resistance (R_p) at 700 °C in air. The rate limiting step for oxygen reduction reaction (ORR) is the charge transfer process. La₂Cu_0.8Co_0.2O₄ cathode exhibits the lowest overpotential of about 50 mV at a current density of 48 mA cm⁻² at 700 °C in air.     

The role of CuO modified La0·7Sr0·3FeO3 perovskite on intermediate-temperature partial oxidation of methane via chemical looping scheme

Synthesis gas production via chemical-looping partial oxidation (CLPO) of methane reduces operating cost and likely avoids carbon dioxide emissions. Previous studies exhibit La_0·7Sr_0·3FeO₃ (LSF) a good high-temperature oxygen carrier, but not being applicable in intermediate-temperature CLPO processes. This work proposes a CuO modified LSF (xCuO/LSF, x = 2,5,10,15) for enhancing the reactivity of oxygen carriers at relatively low temperatures. Characterization methods, including N₂ physisorption, ICP-OES, H₂-TPR, XRD and XPS, are implemented to determine properties of xCuO/LSF. Fixed-bed experiments determine the best candidate under 750 °C is 10CuO/LSF. The methane conversion rate of 10CuO/LSF is more than 3 times compared to that of unmodified LSF and the concentration of syngas increases by 375% with the H₂/CO molar ratio of about 2.5. The regenerability of 10CuO/LSF proves to be good. This study provides a promising and simple way to lower the operating temperature of the CLPO process, likely leading a considerable energy saving.     

Study on Sm1.8Ce0.2CuO4-Ce0.9Gd0.1O1.95 composite cathode materials for intermediate temperature solid oxide fuel cell

Sm_1.8Ce_0.2CuO₄-xCe_0.9Gd_0.1O_1.95 (SCC-xCGO, x = 0-12 vol.%) composite cathodes supported on Ce_0.9Gd_0.1O_1.95 (CGO) electrolyte are studied for applications in IT-SOFCs. Results show that Sm_1.8Ce_0.2CuO₄ material is chemically compatible with Ce_0.9Gd_0.1O_1.95 at 1000 °C. The composite electrode exhibits optimum microstructure and forms good contact with the electrolyte after sintering at 1000 °C for 4 h. The polarization resistance (R_p) reduces to the minimum value of 0.17 Ω cm² at 750 °C in air for SCC-CGO06 composite cathode. The relationship between R_p and oxygen partial pressure indicates that the reaction rate-limiting step is the surface diffusion of the dissociative adsorbed oxygen on the composite cathode.     

La1-xSrxFeO3 perovskite-type oxides for chemical-looping steam methane reforming: Identification of the surface elements and redox cyclic performance

We report a family of perovskite-type oxides La_1-xSr_xFeO₃ (x = 0.1, 0.3, 0.5, 0.7, 1.0) prepared by combustion method as effective redox catalysts for methane partial oxidation and thermochemical water splitting in a cyclic redox scheme. The effect of Sr-doping on the characterizations and properties of these perovskite-type oxides were studied by means of X-ray diffraction (XRD), hydrogen temperature-programmed reduction (H₂-TPR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM). All the as-prepared and regenerated samples with various Sr substitutions exhibited pure crystalline perovskite structure. The oxygen carrying capacity of the La_1-xSr_xFeO₃ perovskites was improved by doping Sr into the La-site. Besides, Sr-substitution has obvious effects on the valences of the Fe cations in the B-site and the oxygen species distribution of the La_1-xSr_xFeO₃ perovskites. We recommend La_0.7Sr_0.3FeO₃ as the optimal oxygen carrier in the series because it gives the maximum O_la/O_ad (O_la and O_ad stand for lattice oxygen and adsorbed oxygen species, respectively.) ratio of 3.64:1, which can be regarded as a criterion for the reactivity and selectivity of partial oxidation of methane into syngas of the oxygen carriers. Up to 80% CH₄ conversion in the methane partial oxidation step and 96% of H₂ concentration in the water splitting step were achieved in ten successive redox tests conducted in a fixed bed reactor at 850 °C with La_0.7Sr_0.3FeO₃ as a redox catalyst. The electronic properties of the original LaFeO₃ cell and its lattice substituted by Sr were calculated based on the density functional theory method. Electronic structure analysis demonstrates that doping of Sr makes LaFeO₃ more electric conductive and its electron is prone to be excited. This is in agreement with the test results that La_0.7Sr_0.3FeO₃ exhibited better performance in chemical looping reactions.     

Electrode redox properties of Ba1−xLaxFeO3−δ as cobalt free cathode materials for intermediate-temperature SOFCs

Cobalt-free perovskite oxides Ba_1−xLa_xFeO_3−δ (x = 0.1–0.4) were synthesized by glycine-nitrate combustion method and investigated as a candidate cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). Cubic perovskite structure was obtained when 10–20 mol% La was substituted at Ba-site in Ba_1−xLa_xFeO_3−δ, and the crystal structure was transformed from cubic structure into orthorhombic one at x ≥ 0.2 with an addition of lanthanum doping. The thermal expansion coefficients of Ba_1−xLa_xFeO_3−δ oxides decreased gradually with La content due to increasing electrostatic attraction forces. A gradual increase existed in electrical conductivity tendency with La content due to disproportionation of Fe³⁺ and the larger extent of electron clouds. The electrode redox performance was investigated by electrochemical impedance spectroscopy. Among Ba_1−xLa_xFeO_3−δ series oxides, Ba_0.9La_0.1FeO_3−δ exhibited the best electrochemical performance. The area specific resistance (ASR) of Ba_0.9La_0.1FeO_3−δ was 0.079 Ω cm², 0.37 Ω cm², and 2.15 Ω cm² at 800, 700 and 600 °C under open circuit potential. To investigate electrochemical performances after cathodic polarization, bias potentials were employed on Ba_1−xLa_xFeO_3−δ cathode at 650–800 °C. The results demonstrated the potential applications for Ba_0.9La_0.1FeO_3−δ as cathode materials for IT-SOFCs as a tradeoff between electrochemical and thermal expansion performance.     

Intermediate temperature single-chamber methane fed SOFC based on Gd doped ceria electrolyte and La0.5Sr0.5CoO3−δ as cathode

Single-chamber fuel cells with electrodes supported on an electrolyte of gadolinium doped ceria Ce_1−xGd_xO_2−y with x = 0.2 (CGO) 200 μm thickness has been successfully prepared and characterized. The cells were fed directly with a mixture of methane and air. Doped ceria electrolyte supports were prepared from powders obtained by the acetyl-acetonate sol–gel related method. Inks prepared from mixtures of precursor powders of NiO and CGO with different particle sizes and compositions were prepared, analysed and used to obtain optimal porous anodes thick films. Cathodes based on La_0.5Sr_0.5CoO₃ perovskites (LSCO) were also prepared and deposited on the other side of the electrolyte by inks prepared with a mixture of powders of LSCO, CGO and AgO obtained also by sol–gel related techniques. Both electrodes were deposited by dip coating at different thicknesses (20–30 μm) using a commercial resin where the electrode powders were dispersed. Finally, electrical properties were determined in a single-chamber reactor where methane, as fuel, was mixed with synthetic air below the direct combustion limit. Stable density currents were obtained in these experimental conditions. Temperature, composition and flux rate values of the carrier gas were determinants for the optimization of the electrical properties of the fuel cells.     

Electrocatalytic performance of Ni modified MnOx/C composites toward oxygen reduction reaction and their application in Zn–air battery

A series of Ni modified MnO_x/C composites were synthesized by introducing NaBH₄ to MnO₂/C aqueous suspension containing Ni(NO₃)₂. The physical properties and the activity of the composites toward the oxygen reduction reaction (ORR) were investigated via transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and the electrochemical techniques. The results show that the higher activity of the composites toward the ORR is correlated with the higher content of MnOOH species transformed from Mn(II) on the surface of the composite. The main nickel species in the composites is Ni(OH)₂, while Ni(OH)₂ shows little activity toward the ORR. However, introducing Ni(OH)₂ with proper amount into the MnO_x/C improves the distribution of the active material MnO_x, which contributes to a surface with more MnOOH. The optimal composite is of the Ni/Mn atomic ratio of 1:2 and the MnO_x loading of 28 wt.%. The maximum power density of the zinc–air battery with the optimized Ni modified MnO_x/C as the cathode catalyst reaches up to 122 mW cm⁻², much higher than the one with the MnO_x/C as the air cathode catalyst (89 mW cm⁻²), and slightly higher than those with the Pd/C and Pt/C as the cathode catalysts.     

Electrochemical performance of Nd1.93Sr0.07CuO4 nanofiber as cathode material for SOFC

Nd_1.93Sr_0.07CuO₄ nanofibers are prepared by electrospinning technique followed by a simple thermal treatment. The morphology and phase evolution of as-obtained fibers are characterized by TG-DTA, XRD, FT-IR and SEM, respectively. Typical ceramic fiber diameter is 100–200 nm, with length exceeding tens of microns. Rapid heating the nanofiber cathode at 1000 °C for 15 min results in homogeneous porous microstructure and good contact with the CGO electrolyte. EIS analysis of the nanofiber electrode gives a polarization resistance of 0.26 Ω cm² at 700 °C in air, two times smaller than that from the powder cathode with the same composition. The excellent electrochemical performance can be attributed to the well constructed microstructure of the fiber cathode, which can promote surface oxygen diffusion or adsorption processes on the cathode.     

Co-deficient PrBaCo2−xO6−δ perovskites as cathode materials for intermediate-temperature solid oxide fuel cells: Enhanced electrochemical performance and oxygen reduction kinetics

Co-deficient PrBaCo_2?xO_6?δ perovskites (x = 0, 0.02, 0.06 and 0.1) are synthesized by a solid-state reaction, and the effects of Co-deficiency on the crystal structure, oxygen nonstoichiometry and electrochemical properties are investigated. The PrBaCo_2?xO_6?δ samples have an orthorhombic layered perovskite structure with double c axis. The degree of oxygen nonstoichiometry increases with decreasing Co content (0 ≤ x ≤ 0.06) and then slightly decreases at x = 0.1. All the samples exhibit the electrical conductivity values of >300 S cm^?1 in the temperature range of 100–800 °C in air, which match well the requirement of cathode. With significantly enhanced electrochemical performance and good chemical compatibility between PrBaCo_2?xO_6?δ and CGO, this system of Co-deficient perovskite is promising cathode material for IT-SOFCs. Among all these components, PrBaCo_1.94O_6?δ gives lowest polarization resistance of 0.059 Ω cm² at 700 °C in air. When tested as cathode in fuel cell, the anode-supported Ni-YSZ|YSZ|CGO|PrBaCo_1.94O_6?δ cell delivers a maximum peak power density of 889 mW cm^?2 at 650 °C, which is higher than that of PrBaCoO_6?δ cathode-based cell (764 mW cm^?2). The oxygen reduction kinetics at the PrBaCo_1.94O_6?δ cathode interface is also explored, and the rate-limiting steps for oxygen reduction reaction are determined.     

Self-assembled Fe-doped PrBaCo2O5+δ composite cathodes with disorder transition region for intermediate-temperature solid oxide fuel cells

PrBa(Co_1-xFe_x)₂O_5+δ polymorphs (0.1 < x < 0.4, denoted as PBCF-x with Fe-doping level x) are reported and dual phase of cubic phase Pr_0.5Ba_0.5Co_1−xFe_xO_3−δ and tetragonal phase PrBa(Co_1-xFe_x)₂O_5+δ are co-produced through an common sol–gel method. The co-generation of the dual-phases leads to the formation of abundant hetero-interfaces between the neighboring crystal phases and the synergic effect demonstrates remarkably high oxygen adsorption and dissociation ability in the air. The density functional theory (DFT) calculation establishes that the existence of hetero-interfaces promotes oxygen reduction reaction activity (ORR) which is crucial to improve cathode performance of proton-conducing solid oxide fuel cells (H–SOFCs). Moreover, an outstanding electrochemical performance is obtained for the single cell with a PBCF03 cathode and the research demonstrates that a self-assemble dual phase cathode can be an effective approach for developing high-performing H–SOFCs.     

Electrochemical characterization of Pr2CuO4 cathode for IT-SOFC

The electrochemical properties of Pr₂CuO₄ (PCO) electrode screen-printed on Ce_0.9Gd_0.1O_1.95 (CGO) electrolyte were investigated. PCO was synthesized by a solid-state route from the stoichiometric mixture of oxides at 1273 K, 20 h. Thermogravimetric analysis (TGA) of PCO both in air and Ar demonstrated its stability up to 1173 K. X-ray powder diffraction study of the PCO–CGO mixture annealed in air at 1173 K for 100 h did not reveal chemical interaction between materials. The oxygen reduction on porous PCO electrodes applied on CGO electrolyte was studied in a symmetrical cell configuration by AC impedance spectroscopy at OCV conditions at 773–1173 K and pO₂$p_{{\text{O}}_2}$ = 10⁻⁴–1 atm. Analysis of the data revealed that depending on temperature and oxygen partial pressure different rate-determining steps of the overall oxygen reduction reaction take place. Calculated value of area specific resistance (ASR) of PCO electrode is 1.7 ± 0.2 Ω cm² at 973 K in air and it is constant after 6 subsequent thermocycles. We have found that oxygen reduction on PCO applied on CGO takes mainly place at the triple-phase boundary (TPB) since Adler–Lane–Steele (ALS) model is not valid. Therefore electrochemical characteristics of PCO electrode can be improved by further optimization of both microstructure of the electrode and electrode/electrolyte interface and PCO can be considered as a promising cathode material for intermediate temperature solid oxide fuel cells (IT-SOFC).     

Tuning activity of Pt/FeOx/TiO2 catalysts synthesized through selective-electrostatic adsorption for hydrogen purification by prox reaction

Hydrogen purification by removing CO traces was studied via the preferential CO oxidation (PROX) reaction using highly dispersed Pt catalysts supported on dual oxide FeO_x/TiO₂. These catalysts were prepared by the strong electrostatic adsorption (SEA) method by varying the pH of synthesis and the calcination temperature. By measuring the point of zero charge (PZC) of the support components, it was possible to determine the pH in which Pt can be selectively deposited onto one of the support components, obtaining Pt dispersion values above 90%. The selective SEA of a Pt precursor onto the co-support (FeO_x) was achieved at a synthesis pH between the PZCs of the support components (i.e., TiO₂ PZC = 5.2 and Fe₂O₃ PZC = 6.9) by using a Pt anionic complex. The catalytic activity for the PROX reaction, expressed in terms of the CO conversion, O₂ selectivity to CO₂, apparent activation energy, and turnover frequency, confirmed that the SEA prepared catalysts were active and selective for the PROX reaction. XPS and TPR results of the Pt/FeO_x/TiO₂ catalysts showed the formation of Pt-FeO_x interfaces, called as (Pt-FeO_x)_i interfacial sites, which enhanced the stability and catalytic activity for the PROX reaction. The concentration of these sites can be controlled by the synthesis conditions used, mainly pH and to a lower extent the calcination temperature.     

A high-performance ceramic composite anode for protonic ceramic fuel cells based on lanthanum strontium vanadate

The composite electrodes for protonic ceramic fuel cells (PCFC) were fabricated by infiltration of (La_0.8Sr_0.2)FeO_3−δ (LSF) cathode and (La_0.7Sr_0.3)V_0.90O_3−δ (LSV) anode into a porous protonic ceramic, Ba(Ce_0.51Zr_0.30Y_0.15Zn_0.04)O_3−δ (BCZY-Zn), respectively. Further, Pd-ceria catalysts were added into the composite anode. In the same method, the oxygen ion conducting fuel cells with the yttria-stabilized zirconia as an electrolyte (YSZ cell) were also fabricated. At 973 K, the non-ohmic area specific resistance (ASR) of PCFC (0.09 Ω cm²) was much smaller than that of the YSZ cell (0.28 Ω cm²) although the protonic conductivity of BCZY-Zn was slightly smaller than the oxygen ion conductivity of YSZ. According to the analysis of the symmetric cells with BCZY-Zn as an electrolyte, the LSV-composite anode showed better performance than the LSF-composite cathode at low temperatures.     

Electrochemical performance of novel NGCO-LSCF composite cathode for intermediate temperature solid oxide fuel cells

In this study, a co-dopant CGO was synthesized to produce more efficient cathode materials for intermediate temperature solid oxide fuel cell (IT-SOFC) applications. Neodymium (Nd) was doped into CGO in four different weight ratios in the formula Nd_xGd_0.15Ce_0.85-xO_2-δ (NGCO); the selected percentages for x were 1%, 3%, 5% and 7%. XRD patterns showed pure phase for all synthesized compositions and good compatibility at high temperature under static air with the most common ceramic cathode material in IT-SOFC (La_0·60Sr_0·40Co_0·20Fe_0·80O_2-ä, LSCF). Impedance spectroscopic characterization of symmetrical cells of the composite NGCO-LSCF at different temperatures (650–800 °C in steps of 50 °C) and a frequency range of 0.1–1 MHz in synthetic air revealed interesting results. The lowest polarization resistance (R_p) was achieved for Nd_0.05Gd_0.15Ce_0·80O_2-δ (0.06 Ω cm² at 800 °C, 0.17 Ω cm² at 750 °C, 0.31 Ω cm² at 700 °C, and 0.59 Ω cm² at 650 °C). The expected decrease in R_p was not observed for the sample with higher Nd content (7% Nd). Thus, it can be said that there is a distinction between the compositions Nd_0.05Gd_0.15Ce_0·80O_2-δ and Nd_0.07Gd_0.15Ce_0·78O_2-δ; the co-doping of Nd in NGCO incremented the oxygen ion diffusion path, thereby optimization in the triple phase boundary (TPB) sites was obtained. Furthermore, SEM and TGA measurements were conducted to clarify the reasons of such improvements. This work showed that an NGCO-LSCF composite can be considered as a potential candidate for cathode material for future IT-SOFC applications.     

Promotion on electrochemical performance of Ba‐deficient Ba1 − xBi0.05Co0.8Nb0.15O3 − δ cathode for intermediate temperature solid oxide fuel cells

Reducing the operating temperature is the developing trend for solid oxide fuel cells. The key is to develop the cathode with high electrocatalytic activity for oxygen reduction reaction operated at reduced temperatures. Ba‐deficient Ba_1 ? xBi_0.05Co_0.8Nb_0.15O_3 ? δ (Ba_1 ? xBCN, 0 ≤ x ≤ 0.10) are synthesized by solid‐state reaction method and evaluated as novel cathodes for intermediate‐temperature solid oxide fuel cells. Ba_1 ? xBCN is preserved to primitive cubic perovskite phase and meets the compatibility requirement with gadolinium doped ceria oxide (GDC) electrolyte at 950°C. Though the Ba deficiency distorts the cell symmetry, it improves the charge transfer steps rapidly, ascribing to the improvement of oxygen vacancy concentration. The polarization resistance of Ba_0.95BCN is as low as 0.056 Ω cm² in air at 700°C. The peak power density of the single cell with this cathode is as high as 1.41 W cm^?2 at 750°C with wet H₂ as fuel and air as oxidant, indicating the great potential for enhanced performance of Co‐based cathodes with A‐site deficiency.