Ca and Pr substitution promoted the cell performance in LnSr3Fe3O10-δ cathode for solid oxide fuel cells

The substitution of Ca for Sr in the LnSr_3-xCa_xFe₃O_10-δ (x = 0–1.5, Ln = La, Pr, and Sm), Ruddlesden-Popper (RP) intergrowth structure was investigated to determine how the physical and electrochemical properties of this potential cathode material in solid oxide fuel cells (SOFCs) are impacted. A small amount of Ca incorporated into the structure reduced the thermal expansion coefficient, improved the electrical conductivity, and increased power density by up to 30% of a La_0.8Sr_0.2Ga_0.8Mg_0.2O₃ electrolyte-supported single cell. The microstructure and oxygen permeability of the materials were independent of Ca substitution. A phase transformation of LaSr_3-xCa_xFe₃O_10-δ to perovskite was observed when the Ca composition of x > 1.0. Among the substitution of Pr and Sm for La in LaSr_2.7Ca_0.3Fe₃O_10-δ, only PrSr_2.7Ca_0.3Fe₃O_10-δ was pure with no phase transformation found. The co-substitution of Pr and Ca promoted the reduction of Fe, enhanced the oxygen permeation and active surface, and diminished the contact resistance at the cathode-electrolyte interlayer. The co-substitution of Ca and Pr delivered good electrochemical performance of approximately 354 mWcm⁻² at 800 °C on a 0.3 mm thick La_0.8Sr_0.2Ga_0.8Mg_0.2O₃ electrolyte-supported cell and the lowest area specific resistance (ASR).     

Characterization of Ba0.5Sr0.5M1−xFexO3−δ (M = Co and Cu) perovskite oxide cathode materials for intermediate temperature solid oxide fuel cells

Ba_0.5Sr_0.5Co_1?xFe_xO_3?δ (x = 0.2, 0.6, and 0.8) and Ba_0.5Sr_0.5Cu_1?xFe_xO_3?δ (x = 0.6 and 0.8) perovskite oxides have been investigated as cathode materials for intermediate temperature solid oxide fuel cells. All the samples synthesized by a citrate–EDTA complexing method were single-phase cubic perovskite solid solutions. Then, the thermal expansion coefficient, electrical conductivities, the oxygen vacancy concentrations, the polarization resistances (R_p), and the power densities were measured. An increase in the Co content resulted in a decrease in the polarization resistance, the electrical conductivities at low temperatures, and the inflection point of the thermal expansion coefficient, but it led to an increase in the electrical conductivities at high temperatures, the oxygen vacancy concentrations, and the maximum power densities. The Cu-based system has similar behavior to the Co-based system; yet, in terms of the electrical conductivities, high Cu content gave a better result than low content for the entire range of temperatures.     

Synthesis and characterization of Ca3-xLaxCo4-yCuyO9+δ cathodes for intermediate temperature solid oxide fuel cells

The calcium cobaltite Ca_3-xLa_xCo_4-yCu_yO_9+δ with x and y = 0 and 0.1 were synthesized and the electrical, thermal, and catalytic behaviors for the oxygen reduction reaction (ORR) for use as air electrodes in intermediate-temperature solid oxide fuel cells (IT-SOFCs) were evaluated. X?ray diffraction confirms the Ca_3-xLa_xCo_4-yCu_yO_9+δ samples were crystallized in a monoclinic structure and scanning electron microscopic image shows lamella-like grain formation. Introduction of dopants decreases slightly the loss of lattice oxygen and thermal expansion co-efficient. The Ca_3-xLa_xCo_4-yCu_yO_9+δ samples exhibit good phase stability for long-term operation, thermal expansion, and chemical compatibility with the Ce_0.8Gd_0.2O_2-δ electrolyte. Among the studied samples, Ca_2.9La_0.1Co₄O_9+δ shows a maximum conductivity of 176 Scm^?1 at 800 °C. Although the doped samples exhibit a higher total electrical conductivity, an improved symmetrical cell performance is displayed by the undoped sample. Comparing the sintering temperatures, the composite cathode Ca₃Co₄O_9+δ + Ce_0.8Gd_0.2O_2-δ sintered at 800 °C exhibit the lowest area specific resistance of 0.154 Ω cm² at 800 °C in air. In the Ca_3-xLa_xCo_4-yCu_yO_9+δ + GDC composite cathodes, the charge-transfer process at high frequencies presents a major rate limiting step for the oxygen reduction reaction.     

SrCo1−xSbxO3−δ cathode materials prepared by Pechini method for solid oxide fuel cell applications

In this study, SrCo_1?ySb_yO_3?δ powders were prepared by a modified Pechini method. According to the study results, the cubic Pm3m phase of the SrCo_1?ySb_yO_3?δ ceramics was obtained as 10% of cobalt ions were substituted by antimony ions. Doping of Sb³⁺ ions appeared both to stabilize the Pm3m phase of the SrCo_1?ySb_yO_3?δ ceramics and to enhance densification and retard grain growth. The coefficient of thermal expansion of the SrCo_1?xSb_xO_3?δ ceramics increased with the content of the antimony ions, ranging from 10.17 to 15.37 ppm/°C at temperatures lower than the inflection point (ranging from 450 °C to 550 °C) and from 22.16 to 29.29 ppm/°C at higher temperatures. For the SrCo_0.98Sb_0.02O_3?δ ceramic, electrical conductivity reached a maximum of 507 S/cm at 450 °C. The ohmic and polarization resistances of the single cell with the pure SrCo_0.98Sb_0.02O_3?δ cathode at 700 °C read respectively 0.298 Ω cm² and 0.560 Ω cm². The single cell with the SrCo_0.98Sb_0.02O_3?δ-SDC composite cathode appeared to reduce the impedances with the R₀ and R_P at 700 °C reading respectively 0.109 Ω cm² and 0.127 Ω cm². Without microstructure optimization and measured at 700 °C, the single cells with the pure SrCo_0.98Sb_0.02O_3?δ cathode and the SrCo_0.98Sb_0.02O_3?δ-SDC composite cathode, demonstrated maximum power densities of 0.100 W/cm² and 0.487 W/cm². Apparently, SrCo_1?ySb_yO_3?δ is a potential cathode for use in IT-SOFCs.     

Electrochemical performance of La2NiO4+δ cathode for intermediate-temperature solid oxide fuel cells

The application of the La₂NiO_4+δ (LNO), one of the Ruddlesden–Popper series materials, as a cathode material for intermediate temperature solid oxide fuel cells is investigated in detail. LNO is synthesized via a complex method using ethylenediaminetetraacetic acid (EDTA) and citric acid. The effect of the calcination temperature of the LNO powder and the sintering temperature of the LNO cathode layer on the anode-supported cell, Ni–YSZ/YSZ/GDC/LNO, is characterized in view of the charge transfer resistance and the mass transfer resistance. Charge transfer resistance was not significantly affected by calcination and sintering temperature when the sintering temperature was not lower than the calcination temperature. Mass transfer resistance was primarily governed by the sintering temperature. The unit cell with the LNO cathode sintered at 1100 °C with 900 °C-calcined powder presented the lowest polarization resistance for all the measured temperatures and exhibited the highest fuel cell performances, with values of 1.25, 0.815, 0.485, and 0.263 W cm⁻² for temperatures of 800, 750, 700, and 650 °C, respectively.     

Characteristics of LaCo0.4Ni0.6-xCuxO3-δ ceramics as a cathode material for intermediate-temperature solid oxide fuel cells

In this study, the effects of Cu-ion substitution on the densification, microstructure, and physical properties of LaCo_0.4Ni_0.6-xCu_xO_3-δ ceramics were investigated. The results indicate that doping with Cu ions not only enhances the densification but also promotes the grain growth of LaCo_0.4Ni_0.6-xCu_xO_3-δ ceramics. The Cu substitution at x ≤ 0.2 can suppress the formation of La₄Ni₃O₁₀, while the excess Cu triggers the formation of La₂CuO_4.032 phase. The p-type conduction of LaCo_0.4Ni_0.6O_3-δ ceramic was significantly raised by Cu substitution because the acceptor doping ($\begin{array}{c}\hfill \begin{array}{c}\hfill \begin{array}{c}\hfill \begin{array}{c}\hfill C{u}_{Ni}^{\text{'}}\hfill \end{array}\hfill \end{array}\hfill \end{array}\hfill \end{array}$) triggered the formation of hole carriers; this effect was maximized in the case of LaCo_0.4Ni_0.4Cu_0.2O_3-δ composition (1480 S cm^?1 at 500 °C). Thermogravimetric data revealed a slight weight increase of 0.29% for LaCo_0.4Ni_0.4Cu_0.2O_3-δ compact up to 871 °C; this is due to the incorporation of oxygen that creates metal vacancies and additional $\begin{array}{c}\hfill \begin{array}{c}\hfill \begin{array}{c}\hfill \begin{array}{c}\hfill \begin{array}{c}\hfill h^{?}\hfill \end{array}\hfill \end{array}\hfill \end{array}\hfill \end{array}\hfill \end{array}$carriers, partially compensating the conductivity loss due to the spin-disorder scattering. As the temperature of the LaCo_0.4Ni_0.4Cu_0.2O_3-δ compacts rose above 871 °C, significant weight loss with temperature was observed because of the release of lattice oxygen to the ambient air as a result of Co (IV) thermal reduction accompanied by the formation of oxygen vacancies. A solid oxide fuel cell (SOFC) single cell with Sm_0.2Ce_0.8O_2-δ (electrolyte) and LaCo_0.4Ni_0.4Cu_0.2O_3-δ (cathode) was built and characterized. The Ohmic (0.256 Ω cm²) and polarization (0.434 Ω cm²) resistances of the single cell at 700 °C were determined; and the maximum power density was 0.535 W cm^?2. These results show that LaCo_0.4Ni_0.4Cu_0.2O_3-δ is a very promising cathode material for SOFC applications.     

Electrical properties of (La0.9Ca0.1)(Co1−xNix)O3−δ cathode materials for SOFCs

Modified perovskite ceramics (La_0.9Ca_0.1)(Co_1?xNi_x)O_3?δ (x = 0–0.3) cathodes for solid oxide fuel cells (SOFCs) were synthesized by solid state reaction. The lattice parameters, electrical conductivity, activation energy, and microstructures of these specimens were investigated systematically in this study. The results exhibited that all specimens are rhombohedron structures and their tolerance factors were greater than 0.97, indicating that the perovskite was not distorted by Ni²⁺ cation substitution for the B site of (La_0.9Ca_0.1)CoO_3?δ. The microstructures of the (La_0.9Ca_0.1)(Co_1?xNi_x)O_3?δ specimens showed good densification, and were well-sintered, with few pores. The electrical conductivity behavior conformed to the nature of a semiconductor, for all specimens. As x = 0.1, the electrical conductivity reached the maximum value of 750.3 S/cm at 800 °C, and the activation energy calculated from the Arrhenius plot of the electrical conductivity versus the reciprocal of temperature is 7.1 kJ/mol.The novelty of this study is its introduction of the concept of defect chemistry to explain the relationship between compensation mechanisms and electrical conductivity. The information gleaned regarding charge compensation mechanisms and defect formation may be valuable for a better understanding of the cathode of (La_0.9Ca_0.1)(Co_1?xNi_x)O_3?δ ceramics used for SOFCs. Moreover, the information about oxygen content versus temperature is useful for expressing the relationship between electrical conductivity and composition. Therefore, we also used thermogravimetric analysis combined with the room-temperature oxygen content which was determined by iodometric titration to investigate the oxygen content from room temperature to high temperature, in air. Based on the experimental results, the (La_0.9Ca_0.1)(Co_0.9Ni_0.1)O_3?δ specimen shows high electrical conductivity. Consequently, it is identified as a promising candidate for cathode SOFC applications.     

Ba0.95La0.05Fe0.8Ni0.2O3−δ perovskite as efficient cathode electrocatalysts for proton-conducting solid oxide fuel cells

The key issue that limits the electrochemical performance of proton-conducting solid oxide fuel cells (H⁺-SOFCs) is the sluggish kinetics of the oxygen reduction reaction (ORR) of cathode at intermediate and low temperatures. Herein, oxygen vacancy engineering is conducted on cobalt-free Ba_0.95La_0.05FeO_3?δ (BLF) by nickel substitution, which is confirmed by density functional theory computations. Nickel-substituted BLF material (Ba_0.95La_0.05Fe_1?xNi_xO_3?δ (x = 0, 0.1, 0.2, 0.3)) can promote the generation of oxygen vacancies and improve catalytic activity, which is found to be in line with the experimental results of XPS. The phase structure, microstructure, and electrochemical performance of Ba_0.95La_0.05Fe_0.8Ni_0.2O_3?δ (BLFNi0.2) are well-investigated. The single cells with the BLFNi0.2-BaCe_0.7Zr_0.1Y_0.1Yb_0.1O_3?δ (BCZYYb) composite cathode achieve low polarization resistance (R_p) of 0.099 Ω cm² and a peak power density of 631 mW cm^?2 at 700 °C while maintaining good durability for 120 h with no observable degradation. The results demonstrate that Ni-doped BLF is a promising cobalt-free cathode material for H⁺-SOFCs.     

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).     

Evaluation of GdBaCuCo0.5Fe0.5O5+δ as cathode material for intermediate temperature solid oxide fuel cells

The GdBaCuCo_0.5Fe_0.5O_5+δ (GBCCF) layered perovskite oxide was evaluated as novel cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). Its electrical conductivity was 9–13 S cm^?1 at 650–800 °C in air. The average thermal expansion coefficient (TEC) of GBCCF was 14.4 × 10^?6 K^?1, which was close to that of the typical electrolyte material. The cathode polarization resistance of GBCCF was 0.650 Ω cm² at 750 °C and it decreases to 0.118 Ω cm² when Ce_0.9Gd_0.1O_1.95 (GDC) was added to form a GBCCF–GDC composite cathode. Preliminary results indicated that layered perovskite GBCCF was a promising alternative cathode material for IT-SOFCs.     

Highly electrocatalytic activity Ruddlesden−Popper type electrode materials for solid oxide fuel cells

To promote the viability of commercial solid oxide fuel cell (SOFC), developing novel oxygen electrodes with high electrochemical activity is essential. Herein, a series Ruddlesden-Popper oxides, Sr_3?xLa_xFe₂O_7?δ (SLFx), are successfully synthesized and evaluated as potential cathode materials for SOFC. The oxygen desorption behavior, electrochemical activity and oxygen reduction reaction (ORR) kinetics of the SLFx cathodes are systematically discussed. The Sr_2.9La_0.1Fe₂O_7?δ (SLF10) cathode exhibits highest oxygen vacancy concentration and excellent electrocatalytic performance, as evidenced by a low polarization resistance of 0.14 Ω cm² and high maximum power density of 0.77 W cm^?2 at 700 °C. From electrochemical impedance spectra and distribution of relaxation times analysis, the oxygen adsorption/desorption process is the rate-limiting step toward ORR at the cathode interface. Furthermore, SLF10 shows considerable polarization overpotentials in both SOFC and solid oxide electrolysis cell (SOEC) modes, indicating that SLF10 is a promising bifunctional electrode for electrocatalytic oxygen reaction.     

Electrochemical and microstructural characteristics of nanoperovskite oxides Ba0.2Sr0.8Co0.8Fe0.2O3−δ (BSCF) for solid oxide fuel cells

Nanoperovskite oxides, Ba_0.2Sr_0.8Co_0.8Fe_0.2O_3?δ (BSCF), were synthesized via the co-precipitation method using Ba, Sr, Co, and Fe nitrates as precursors. Next, half cells were fabricated by painting BSCF thin film on Sm_0.2Ce_0.8O_x (samarium doped ceria, SDC) electrolyte pellets. X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical impedance spectroscopy (EIS) measurements were carried out on the BSCF powders and pellets obtained after sintering at 900 °C. Investigations revealed that single-phase perovskites with cubic structure was obtained in this study. The impedance spectra for BSCF/SDC/BSCF cells were measured to obtain the interfacial area specific resistances (ASR) at several operating temperatures. The lowest values of ASR were found to be 0.19 Ω cm², 0.14 Ω cm² 0.10 cm², 0.09 Ω cm² and 0.07 Ω cm² at operating temperatures of 600 °C, 650 °C, 700 °C, 750 °C and 800 °C, respectively. The highest conductivity was found for cells sintered at 900 °C with an electrical conductivity of 153 S cm^?1 in air at operating temperature of 700 °C.     

Insight of BaCe0.5Fe0.5O3−δ twin perovskite oxide composite for solid oxide electrochemical cells

One-pot synthesized twin perovskite oxide composite of BaCe_0.5Fe_0.5O_3−δ (BCF), comprising cubic and orthorhombic perovskite phases, shows triple-conducting properties for promising solid oxide electrochemical cells. Phase composition evolution of BCF under various conditions was systematically investigated, revealing that the cubic perovskite phase could be fully/partially reduced into the orthorhombic phase under certain conditions. The reduction happened between the two phases at the interface, leading to the microstructure change. As a result, the corresponding apparent conducting properties also changed due to the difference between predominant conduction properties for each phase. Based on the revealed phase composition, microstructure, and electrochemical properties changes, a deep understanding of BCF's application in different conditions (oxidizing atmospheres, reducing/oxidizing gradients, cathodic conditions, and anodic conditions) was achieved. Triple-conducting property (H⁺/O²⁻/e⁻), fast open-circuit voltage response (∼16–∼470 mV) for gradients change, and improved single-cell performance (∼31% lower polarization resistance at 600°C) were comprehensively demonstrated. Besides, the performance was analyzed under anodic conditions, which showed that the microstructure and phase change significantly affected the anodic behavior.     

Synthesis and applications of composite cathode based on Sm0.5Sr0.5Co3−δ for solid oxide fuel cell

Cobaltite based perovskites, such as Sm_0.5Sr_0.5Co_3?δ (SSC), are attractive solid oxide fuel cell (SOFC) cathodes due to their high electrochemical activity and electrical conductivity. To obtain higher fuel cell performance with smaller particles, nano-sized SSC powders were synthesized by a complex method with/without carbon black, HB170. However, during synthesis, carbon black reacted with Sr, and unfortunately formed SrCO₃. To obtain pure perovskite SSC, a calcination temperature of 900 °C is needed. At 680 °C, an SOFC with SSC (calcined at 700 °C and synthesized without HB170) exhibited a higher fuel cell performance, of 0.68W·cm^?2, than that with SSCHB (calcined at 900 °C and synthesized with HB170), of 0.58W·cm^?2. Adding GDC for composite cathode is more effective in SSCHB porous cathodes than in SSC porous cathodes. At 680 °C, the composite cathode of SSCHB6-GDC4 exhibited the highest maximum power density of 0.72W·cm^?2 which results from the combined effects of lowered charge transfer polarization and mass transfer polarization. To obtain higher fuel cell performance, optimum composition and processes are necessary.     

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.     

Nanofiber-based LaxSr1−xTiO3-GdyCe1−yO2−δ composite anode for solid oxide fuel cells

La_xSr_1−xTiO₃ (LST) nanofibers with pure perovskite structure, smooth surface, uniform diameter and length are prepared by electrospinning technique, and applied as scaffolds of La_xSr_1−xTiO₃-Gd_yCe_1−yO_2−δ (LST-GDC) composite anodes for SOFCs. The optimal La doping ratio of LST scaffold has been found to be 0.4, and 0.2 the optimal Gd doping ratio of GDC impregnation phase. The LST:GDC optimal mass ratio of nanofiber-based composite anode has been found to be 1:1.5481, and the composite anode (electrolyte is yttria-stabilized zirconia) to show low interfacial polarization resistances of 0.7309, 0.4688 and 0.2966 Ω cm² at 800, 850 and 900 °C, respectively. In addition, the microstructure of LST materials has been found to plays an important role on the electrochemical performance of the anodes, and the LST nanofiber scaffolds to show the higher porosity leading to a larger triple phase (ionic conduction phase, electronic conduction phase and gas phase) boundary (TPB) area for the composite anodes.     

Ce0.9Gd0.1O1.95 supported La0.6Sr0.4Co0.2Fe0.8O3−δ cathodes for solid oxide fuel cells

Lanthanum-based iron- and cobalt-containing perovskite has a high potential as a cathode material because of its high electro-catalytic activity at a relatively low operating temperature in solid oxide fuel cells (SOFCs) (600–800). To enhance the electro-catalytic reduction of oxidants on La_0.6Sr_0.4Co_0.2Fe_0.8O_3?δ (LSCF), Ga doped ceria (Ce_0.9Gd_0.1O_1.95, GDC) supported LSCF (15LSCF/GDC) is successfully fabricated using an impregnation method with a ratio of 15 wt% LSCF and 85 wt% GDC. The cathodic polarization resistances of 15LSCF/GDC are 0.015 Ω cm², 0.03 Ω cm², 0.11 Ω cm², and 0.37 Ω cm² at 800 °C, 750 °C, 700 °C, and 650 °C, respectively. The simply mixed composite cathode with LSCF and GDC of the same compositions shows 0.05 Ω cm², 0.2 Ω cm², 0.56 Ω cm², and 1.20 Ω cm² at 800 °C, 750 °C, 700 °C, and 650 °C, respectively. The fuel cell performance of the SOFC with 15LSCF/GDC shows maximum power densities of 1.45 W cm^?2, 1.2 W cm^?2, and 0.8 W cm^?2 at 780 °C, 730 °C, and 680 °C, respectively. GDC supported LSCF (15LSCF/GDC) shows a higher fuel cell performance with small compositions of LSCF due to the extension of triple phase boundaries and effective building of an electronic path.     

Evaluation of (Ba0.5Sr0.5)0.85Gd0.15Co0.8Fe0.2O3−δ cathode for intermediate temperature solid oxide fuel cell

A perovskite-type (Ba_0.5Sr_0.5)_0.85Gd_0.15Co_0.8Fe_0.2O_3?δ (BSGCF) oxide has been investigated as the cathode of intermediate temperature solid oxide fuel cells (IT-SOFCs). Coulometric titration, thermogravimetry analysis, thermal expansion and four-probe DC resistance measurements indicate that the introduction of Gd³⁺ ions into the A-site of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3?δ (BSCF) leads to the increase in both oxygen nonstoichiometry at room temperature and electrical conductivity. For example, the conductivity of BSGCF is 148 S cm^?1 at 507 °C, over 4 times as large as that of BSCF. Furthermore, the electrochemical activity toward the oxygen reduction reaction is also enhanced by the Gd doping. Impedance spectra conducted on symmetrical half cells show that the interfacial polarization resistance of the BSGCF cathode is 0.171 Ω cm² at 600 °C, smaller than 0.297 Ω cm² of the BSCF cathode. A Ni/Sm_0.2Ce_0.8O_1.9 anode-supported single cell based on the BSGCF cathode exhibits a peak power density of 551 mW cm^?2 at 600 °C.     

Evaluation of bismuth doped La2-xBixNiO4+δ (x = 0, 0.02 and 0.04) as cathode materials for solid oxide fuel cells

Bismuth doped La_2-xBi_xNiO_4+δ (x = 0, 0.02 and 0.04) oxides are investigated as SOFC cathodes. The effects of Bi doping on the phase structure, thermal expansion, electrical conduction behavior as well as electrochemical performance are studied. All the samples exist as a tetragonal Ruddlesden-Popper structure. Bi-doped LBNO-0.02 and LBNO-0.04 have good chemical and thermal compatibility with LSGM electrolyte. The average TEC over 20–900°С was 13.4 × 10^?6 and 14.2 × 10^?6 K^?1 for LBNO-0.02 and LBNO-0.04, respectively. The electrical conductivity was decreasing with the rise of Bi doping content. EIS measurement indicates Bi doping can decrease the ASR values. At 750 °C, the obtained ASR for LBNO-0.04 is 0.18 Ωcm², which is 56% lower than that of the sample without Bi doping, suggesting Bi doping is beneficial to the electrochemical catalytic activity of LBNO cathodes.     

Combustion Synthesis of PrBa2Cu3O7−δ and YBa2Cu3O7−δ cuprate materials

PrBaCuO and YBaCuO cuprate materials were prepared from cooper, barium peroxide, and yttrium/praseodymium oxide by SHS and standard solid-state synthesis. SHS reactions were carried out using relatively large cooper particles (< 63 im) to obtain small product samples (13 mm in diameter). High ambient temperature was used to stabilize a combustion front in the ignited pellets. Explored was the effect of cooper particles size, starting density, and ambient temperature on phase evolutions in synthesized materials.