Nd0.5Sr0.5Fe0.8Cu0.2O3−δ–xSm0.2Ce0.8O1.9 cobalt-free composite cathodes for intermediate temperature solid oxide fuel cells

Cobalt-free composites Nd_0.5Sr_0.5Fe_0.8Cu_0.2O_3−δ (NSFCu)–xSm_0.2Ce_0.8O_1.9 (SDC) (x = 0–60 wt%) are investigated as IT-SOFC cathodes. The characteristic properties of cobalt-free composite cathodes comparing to cobalt-based composites are revealed. The DC conductivity and thermal expansion coefficient of the composite cathodes decrease with the content of SDC x, while the polarization resistance R_p shows the least value with addition of 40 wt% of SDC. The power density of the single cell with NSFCu-40% SDC composite cathode improved significantly compared with that of undoped NSFCu cathode, with peak values of 488, 623, 849 and 1052 mW cm⁻² at 600, 650, 700, and 750 °C, respectively. Moreover, the performance of the composite cathode is stable within testing period of 370 h at 700 °C, indicating that the NSFCu-40% SDC is an excellent cobalt-free composite cathode applied in IT-SOFC.     

(La,Pr)0.8Sr0.2FeO3−δ–Sm0.2Ce0.8O2−δ composite cathode for proton-conducting solid oxide fuel cells

Mixed rare-earth (La, Pr)_0.8Sr_0.2FeO_3−δ–Sm_0.2Ce_0.8O_2−δ (LPSF–SDC) composite cathode was investigated for proton-conducting solid oxide fuel cells based on protonic BaZr_0.1Ce_0.7Y_0.2O_3−δ (BZCY) electrolyte. The powders of La_0.8−xPr_xSr_0.2FeO_3−δ (x = 0, 0.2, 0.4, 0.6), Sm_0.2Ce_0.8O_2−δ (SDC) and BaZr_0.1Ce_0.7Y_0.2O_3−δ (BZCY) were synthesized by a citric acid-nitrates self-propagating combustion method. The XRD results indicate that La_0.8−xPr_xSr_0.2FeO_3−δ samples calcined at 950 °C exhibit perovskite structure and there are no interactions between LPSF0.2 and SDC at 1100 °C. The average thermal expansion coefficient (TEC) of LPSF0.2–SDC, BZCY and NiO-BZCY is 12.50 × 10⁻⁶ K⁻¹, 13.51 × 10⁻⁶ K⁻¹ and 13.47 × 10⁻⁶ K⁻¹, respectively, which can provide good thermal compatibility between electrodes and electrolyte. An anode-supported single cell of NiO-BZCY|BZCY|LPSF0.2–SDC was successfully fabricated and operated from 700 °C to 550 °C with humidified hydrogen (∼3% H₂O) as fuel and the static air as oxidant. A high maximum power density of 488 mW cm⁻², an open-circuit potential of 0.95 V, and a low electrode polarization resistance of 0.071 Ω cm² were achieved at 700 °C. Preliminary results demonstrate that LPSF0.2–SDC composite is a promising cathode material for proton-conducting solid oxide fuel cells.     

Characteristics of Ba0.5Sr0.5Co0.8Fe0.2O3−δ–La0.9Sr0.1Ga0.8Mg0.2O3−δ composite cathode for solid oxide fuel cell

Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ–La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ composite cathodes are prepared successfully using combustion synthesis method. Microstructure, chemical compatibility and electrochemical performance have been investigated and analyzed in detail. SEM micrographs show that a structure with porosity and well-necked particles forms after sintering at 1000 °C in the composites. Grain growth is suppressed by addition of La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ phase and grain sizes decrease with increasing weight percent of La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ phase in the composites. Phase analysis demonstrates that chemical compatibility between Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ and La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ is excellent when the weight percent of La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ in the composite is not more than 40%. Through fitting ac impedance spectra, it is found that the ohmic resistance and polarization resistance decrease with increasing La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ content. The polarization resistance reaches a minimum at about 30 and 40 wt.% La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ in the composite.     

Improved oxygen permeability of Ce0.8Sm0.2O2−δ–PrBaCo2O5+δ dual-phase membrane by surface-modifying porous layer

A porous PrBaCo₂O_5+δ or Ce_0.8Sm_0.2O_2−δ–50 vol.% PrBaCo₂O_5+δ (SDC–PBCO (5/5)) layer was deposited on dense Ce_0.8Sm_0.2O_2−δ–40 vol.% PrBaCo₂O_5+δ (SDC–PBCO (6/4)) membrane (450 μm) to enhance the oxygen permeability by increasing the surface area contacting with air. The oxygen permeation flux was measured in the temperature range of 825–945 °C. The results revealed that the oxygen permeation performance of Ce_0.8Sm_0.2O_2−δ–PrBaCo₂O_5+δ membranes can be significantly enhanced by coating SDC–PBCO (5/5) porous layer alone on the surface of feed side. The thickness of modification layer has obvious effect on the permeability of surface modified membrane. The modification on the feed side has much better effect than that on the permeate side. At 945 °C, the oxygen permeation flux of dense SDC–PBCO (6/4) membrane modified by porous SDC–PBCO (5/5) layer is 3.56 × 10⁻⁷ mol cm⁻² s⁻¹, 26% higher than that of the unmodified one.     

Electrical conductivity of cobalt doped La0.8Sr0.2Ga0.8Mg0.2O3−δ

La_0.8Sr_0.2Ga_0.8Mg_0.2O_3−δ (LSGM8282), La_0.8Sr_0.2Ga_0.8Mg_0.15Co_0.05O_3−δ (LSGMC5) and La_0.8Sr_0.2Ga_0.8Mg_0.115Co_0.085O_3−δ (LSGMC8.5) were prepared using a conventional solid-state reaction. Electrical conductivities and electronic conductivities of the samples were measured using four-probe impedance spectrometry, four-probe dc polarization and Hebb–Wagner polarization within the temperature range of 973–1173 K. The electrical conductivities in LSGMC5 and LSGMC8.5 increased with decreasing oxygen partial pressures especially in the high (>10⁻⁵ atm) and low oxygen partial pressure regions (<10⁻¹⁵ atm). However, the electrical conductivity in LSGM8282 had no dependency on the oxygen partial pressure. At temperatures higher than 1073 K, PO₂$P_{{\text{O}}_2}$ dependencies of the free electron conductivities in LSGM8282, LSGMC5 and LSGMC8.5 were about −1/4, and PO₂$P_{{\text{O}}_2}$ dependencies of the electron hole conductivities were about 0.25, 0.12 and 0.07, respectively. Oxygen ion conductivities in LSGMC5 and LSGMC8.5 increased with decreasing oxygen partial pressures especially in the high and low oxygen partial pressure regions, which was due to the increase in the concentration of oxygen vacancies. The change in the concentration of oxygen vacancies and the valence of cobalt with oxygen partial pressure were determined using a thermo-gravimetric technique. Both the electronic conductivity and oxygen ion conductivity in cobalt doped lanthanum gallate samples increased with increasing concentration of cobalt, suggesting that the concentration of cobalt should be optimized carefully to maintain a high electrical conductivity and close to 1 oxygen ion transference number.     

Cathode reaction mechanism of porous-structured Sm0.5Sr0.5CoO3−δ and Sm0.5Sr0.5CoO3−δ/Sm0.2Ce0.8O1.9 for solid oxide fuel cells

The cathode reaction mechanism of porous Sm_0.5Sr_0.5CoO_3−δ, a mixed ionic and electronic conductor (MIEC), is studied through a comparison with the composite cathode Sm_0.5Sr_0.5CoO_3−δ/Sm_0.2Ce_0.8O_1.9. First, the cathodic behaviour of porous Sm_0.5Sr_0.5CoO_3−δ and Sm_0.5Sr_0.5CoO_3−δ/Sm_0.2Ce_0.8O_1.9 are observed for micro-structure and impedance spectra according to Sm_0.2Ce_0.8O_1.9 addition, thermal cycling and long-term properties. The cathode reaction mechanism is discussed in terms of frequency response, activation energy, reaction order and electrode resistance for different oxygen partial pressures p(O₂) at various temperatures. Three elementary steps are considered to be involved in the cathodic reaction: (i) oxygen ion transfer at the cathode-electrolyte interface; (ii) oxygen ion conduction in the bulk cathode; (iii) gas phase diffusion of oxygen. A reaction model based on the empirical equivalent circuit is introduced and analyzed using the impedance spectra. The electrode resistance at high frequency (R_c,HF) in the impedance spectra represents reaction steps (i), due to its fast reaction rate. The electrode resistance at high frequency is independent of p(O₂) at a constant temperature because the semicircle of R_c,HF in the complex plane of the impedance spectra is held constant for different values of p(O₂). Reaction steps (ii) and (iii) are the dominant processes for a MIEC cathode, according to the analysis results. The proposed cathode reaction model and results for a solid oxide fuel cell (SOFC) well describe a MIEC cathode with high ionic conductivity, and assist the understanding of the MIEC cathode reaction mechanism.     

Characteristics of nano La0.6Sr0.4Co0.2Fe0.8O3−δ-infiltrated La0.8Sr0.2Ga0.8Mg0.2O3−δ scaffold cathode for enhanced oxygen reduction

The chemical compatibility and electrochemical properties of nanoLa_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ (LSCF)-infiltrated La_0.8Sr_0.2Ga_0.8Mg_0.2O_3−δ (LSGM) scaffold were manufactured and assessed for the application as a solid oxide fuel cell cathode with an LSGM electrolyte. When the LSCF and LSGM powder mixture was fired above 950 °C, the characteristic peaks of the two materials merged and an insulation peak (derived from LaSrGaO₄) was observed. To prevent reactions between LSCF and LSGM, an infiltration technique was utilized with the LSGM as a scaffold. Using this infiltration technique, nano LSCF particles (approximately 100 nm) can be uniformly coated on the LSGM scaffold surface. Good nano particle adhesion was observed at the LSGM/LSCF interface, even at relatively low firing temperatures (850 °C). The cathode polarization resistance (R_p) of the nano LSCF infiltrated LSGM scaffold cathode was lower than that of a conventional LSCF cathode. The improvement in performance of the nano LSCF-infiltrated cathode was attributed to an increase in the number of triple phase boundaries (TPB) as a result of the nano LSCF coating. In addition, the oxygen reduction reaction (ORR) paths were extended from the TPBs to the LSCF surface because LSCF particles are considerably smaller than the LSCF oxygen ion penetration depth (3–4 μm) over the temperature range of 700 °C–800 °C.     

Evaluation of A-site cation-deficient (Ba0.5Sr0.5)1−xCo0.8Fe0.2O3−δ (x > 0) perovskite as a solid-oxide fuel cell cathode

A-site cation-deficient (Ba_0.5Sr_0.5)_1−xCo_0.8Fe_0.2O_3−δ ((BS)_1−xCF) oxides were synthesized and evaluated as cathode materials for intermediate-temperature solid-oxide fuel cells (ITSOFCs). The material's thermal expansion coefficient, electrical conductivity, oxygen desorption property, and electrocatalytic activity were measured. A decrease in both the electronic conductivity and the thermal expansion coefficient was observed for increasing values of the stoichiometric coefficient, x. This effect was attributed to the creation of additional oxygen vacancies, the suppression of variation in the oxidation states of cobalt and iron, and the suppression of the spin-state transitions of cobalt ions. The increase in A-site cation deficiency resulted in a steady increase in cathode polarization resistance, because impurities formed at the cathode/electrolyte interface, reducing the electronic conductivity. A single SOFC equipped with a BS_0.97CF cathode exhibited peak power densities of 694 and 893 mW cm⁻² at 600 and 650 °C, respectively, and these results were comparable with those obtained with a Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ cathode. Slightly A-site cation-deficient (BS)_1−xCF oxides were still highly promising cathodes for reduced temperature SOFCs.     

Performance of solid oxide electrolysis cells based on composite La0.8Sr0.2MnO3−δ – yttria stabilized zirconia and Ba0.5Sr0.5Co0.8Fe0.2O3−δ oxygen electrodes

The electrochemical performance of solid oxide electrolysis cells (SOECs) having barium strontium cobalt ferrite (Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ) and composite lanthanum strontium manganite–yttria stabilized zirconia (La_0.8Sr_0.2MnO_3−δ–YSZ) oxygen electrodes has been studied over a range of operating conditions. Increasing the operating temperature (973 K to 1173 K) significantly increased electrochemical performance and hydrogen generation efficiency for both systems. The presence of water in the hydrogen electrode was found to have a marked positive effect on the EIS response of solid oxide cell (SOC) under open circuit voltage (OCV). The difference in operation between electrolytic and galvanic modes was investigated. Cells having BSCF oxygen electrodes (Ni–YSZ/YSZ/BSCF) showed greater performance than LSM-YSZ-based cells (Ni–YSZ/YSZ/LSM-YSZ) over the range of temperatures, in both galvanic and electrolytic regimes of operation. The area specific resistance (ASR) of the LSM-YSZ-based cells remained unchanged when transitioning between electrolyser and fuel cell modes; however, the BSCF cells exhibited an overall increase in cell ASR of ∼2.5 times when entering electrolysis mode.     

BaZr0.2Ce0.8−xYxO3−δ solid oxide fuel cell electrolyte synthesized by sol–gel combined with composition-exchange method

This study reports the synthesis of proton-conducting BaZr_0.2Ce_0.8−xY_xO_3−δ (x = 0–0.4) oxides by using a combination of citrate-EDTA complexing sol–gel process and composition-exchange method. Compared to those oxides prepared from conventional sol–gel powders, the sintered BaZr_0.2Ce_0.8−xY_xO_3−δ pellets synthesized by sol–gel combined with composition-exchange method are found to exhibit improved sinterability, a higher relative density, higher conduction, and excellent thermodynamic stability against CO₂. Moreover, the Pt/electrolyte/Pt single cell using such a BaZr_0.2Ce_0.6Y_0.2O_3−δ electrolyte shows an obviously higher maximum powder density in the hydrogen-air fuel cell experiments. Based on the experimental results, we discuss the improvement mechanism in terms of calcined particle characteristics. This work demonstrates that the BaZr_0.2Ce_0.8−xY_xO_3−δ oxides synthesized by sol–gel combined with composition-exchange method would be a promising electrolyte for the use in H⁺-SOFC applications. More importantly, this new fabrication approach could be applied to other similar ABO₃-perovskite material systems.     

Characterization of nanosized Ce0.8Sm0.2O1.9-infiltrated Sm0.5Sr0.5Co0.8Cu0.2O3−δ cathodes for solid oxide fuel cells

This study investigates the microstructure and electrochemical properties of Sm_0.5Sr_0.5Co_0.8Cu_0.2O_3−δ (SSC-Cu) cathode infiltrated with Ce_0.8Sm_0.2O_1.9 (SDC). The newly formed nanosized electrolyte material on the cathode surface, leading the increase in electrochemical performances is mainly attributed to the creation of electrolyte/cathode phase boundaries, which considerably increases the electrochemical sites for oxygen reduction reaction. Based on the experiment results, the 0.4 M SDC infiltration reveals the lowest cathode polarization resistance (R_P), the cathode polarization resistances (R_p) are 0.117, 0.033, and 0.011 Ω cm² at 650, 750, and 850 °C, and the highest peak power density, are 439, 659, and 532 mW cm⁻² at 600, 700, and 800 °C, respectively. The cathode performance in SOFCs can be significantly improved by infiltrating nanoparticles of SDC into an SSC-Cu porous backbone. This study reveals that the infiltration approach may apply in SOFCs to improve their electrochemical properties.     

High performance proton-conducting solid oxide fuel cells with a stable Sm0.5Sr0.5Co3−δ-Ce0.8Sm0.2O2−δ composite cathode

A Sm_0.5Sr_0.5CoO_3−δ-Ce_0.8Sm_0.2O_2−δ (SSC-SDC) composite is employed as a cathode for proton-conducting solid oxide fuel cells (H-SOFCs). BaZr_0.1Ce_0.7Y_0.2O_3−δ (BZCY) is used as the electrolyte, and the system exhibits a relatively high performance. An extremely low electrode polarization resistance of 0.066 Ω cm² is achieved at 700 °C. The maximum power densities are: 665, 504, 344, 214, and 118 mW cm⁻² at 700, 650, 600, 550, and 500 °C, respectively. Moreover, the SSC-SDC cathode shows an essentially stable performance for 25 h at 600 °C with a constant output voltage of 0.5 V. This excellent performance implies that SSC-SDC, which is a typical cathode material for SOFCs based on oxide ionic conductor, is also a promising alternative cathode for H-SOFCs.     

Electrical performance and structural analysis of La1−xBaxGa0.8Mg0.2O3−δ solid electrolyte

The aim of this study was to develop La_1−xBa_xGa_1−yMg_yO_3−δ (x = 0.03–0.1, y = 0.2–0.25) (LBGM) electrolytes for intermediate-temperature solid-oxide fuel cells (SOFCs); these electrolytes were synthesized via a solid-state reaction. In the study, the La_1−xBa_xGa_1−yMg_yO_3−δ samples crystallized in an orthorhombic (Imma) structure, and a BaLaGa₃O₇ phase was detected for x ≥ 0.08 at a fixed y = 0.2. The solubility limit of the Ba ions increased with an increase in the Mg content in the matrix. Two active Raman bands at ca. 677 and 739 cm⁻¹ were observed, and they were attributed to the oxygen vacancies. The La_0.95Ba_0.05Ga_0.75Mg_0.25O_3−δ sample had a higher conductivity ca. 0.1 S/cm at 800 °C, and an activation energy of ca. 0.83–1.27 eV at 500–800 °C. The thermal expansion coefficient (TEC) of the LBGM samples at 200–800 °C was in the range of 10 × 10⁻⁶ to 14 × 10⁻⁶/°C.     

Preparation and characterization of new cobalt-free cathode Pr0.5Sr0.5Fe0.8Cu0.2O3−δ for IT-SOFC

A new cobalt-free perovskite oxide Pr_0.5Sr_0.5Fe_0.8Cu_0.2O_3−δ (PSFC) has been synthesized and evaluated as cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The chemical compatibility of PSFC with Sm_0.2Ce_0.8O_1.9 (SDC) electrolyte has be proven by XRD, and its electrical conductivity reaches the maximum value of 264.1 S cm⁻¹ at 475 °C. Symmetrical cells with the configuration of PSFC/SDC/PSFC are used for the impedance study and the polarization resistance (Rp) of PSFC cathode is as low as 0.050 Ω cm² at 700 °C. Single cells, consisting of Ni–YSZ/YSZ/SDC/PSFC structure, are assembled and tested from 550 °C to 800 °C with wet hydrogen (∼3% H₂O) as fuel and static air as oxidant. A maximum power density of 1077 mW cm⁻² is obtained at 800 °C. All the results suggest that the cobalt-free perovskite oxide PSFC is a very promising cathode material for application in IT-SOFC.     

Fabrication and characterization of Sm0.2Ce0.8O2−δ-Sm0.5Sr0.5CoO3−δ composite cathode for anode supported solid oxide fuel cell

The Sm_0.5Sr_0.5CoO_3−δ (SSC) with perovskite structure is synthesized by the glycine nitrate process (GNP). The phase evolution of SSC powder with different calcination temperatures is investigated by X-ray diffraction and thermogravimetric analyses. The XRD results show that the single perovskite phase of the SSC is completely formed above 1100 °C. The anode-supported single cell is constructed with a porous Ni-yttria-stabilized zirconia (YSZ) anode substrate, an airtight YSZ electrolyte, a Sm_0.2Ce_0.8O_2−δ (SDC) barrier layer, and a screen-printed SSC-SDC composite cathode. The SEM results show that the dense YSZ electrolyte layer exhibits the good interfacial contact with both the Ni-YSZ and the SDC barrier layer. The porous SSC-SDC cathode shows an excellent adhesion with the SDC barrier layer. For the performance test, the maximum power densities are 464, 351 and 243 mW cm⁻² at 800, 750 and 700 °C, respectively. According to the results of the electrochemical impedance spectroscopy (EIS), the charge-transfer resistances of the electrodes are 0.49 and 1.24 Ω cm², and the non charge-transfer resistances are 0.48 and 0.51 Ω cm² at 800 and 700 °C, respectively. The cathode material of SSC is compatible with the YSZ electrolyte via a delicate scheme employed in the fabrication process of unit cell.     

A cobalt-free Sm0.5Sr0.5FeO3−δ–BaZr0.1Ce0.7Y0.2O3−δ composite cathode for proton-conducting solid oxide fuel cells

A cobalt-free Sm_0.5Sr_0.5FeO_3−δ–BaZr_0.1Ce_0.7Y_0.2O_3−δ (SSF–BZCY) was developed as a composite cathode material for proton-conducting solid oxide fuel cells (H-SOFC) based on proton-conducting electrolyte of stable BZCY. The button cells of Ni-BZCY/BZCY/SSF–BZCY were fabricated and tested from 550 to 700 °C with humidified H₂ (～3% H₂O) as a fuel and ambient oxygen as oxidant. An open-circuit potential of 1.024 V, maximum power density of 341 mW cm⁻², and a low electrode polarization resistance of 0.1 Ω cm² were achieved at 700 °C. The experimental results indicated that the SSF–BZCY composite cathode is a good candidate for cathode material.     

(La0.74Bi0.10Sr0.16)MnO3−δ–Ce0.8Gd0.2O2−δ cathodes fabricated by ion-impregnating method for intermediate-temperature solid oxide fuel cells

Porous composite cathodes were fabricated by impregnating (La_0.74Bi_0.10Sr_0.16)MnO_3−δ (LBSM) electronic conducting structure with the ionic conducting Ce_0.8Gd_0.2O_2−δ (GDC) phase. The ion impregnation of the GDC phase significantly enhanced the electrocatalytic activity of the LBSM electrodes for the O₂ reduction reactions, and the ion-impregnated LBSM–GDC composite cathodes showed excellent performance. At 700 °C, the value of the cathode polarization resistance (Rc) was only 0.097 Ω cm² for an ion-impregnated LBSM–GDC cathode, and the performance was gradually improved by increasing the loading of the impregnated GDC. For the performance testing of single cells, the maximum power density was 1036 mW cm⁻² at 700 °C for a cell with the LBSM–GDC cathode. The results demonstrated the unique combination of the LBSM electronic conducting structure with high ionic conducting GDC phase was a valid method to improve the electrode performance, and the ion-impregnated LBSM–GDC was a promising composite cathode material for the intermediate-temperature solid oxide fuel cells.     

Oxygen reduction mechanism at Ba0.5Sr0.5Co0.8Fe0.2O3−δ cathode for solid oxide fuel cell

Perovskite structure Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCF) and La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ (LSGM) powders have been successfully synthesized by glycine–nitrate combustion process. A porous and crack-free BSCF cathode is obtained by spraying the slurry of BSCF powders and terpineol onto LSGM pellet. The oxygen reduction reaction mechanism has been investigated by AC impedance spectroscopy and cyclic voltammetry method. AC impedance spectroscopy analysis shows that there are two different processes in the cathode reaction which are related to oxygen dissociation/adsorption and bulk oxygen diffusion. And the molecular oxygen is involved in the rate-determining step. The polarization resistance decreases with an increase of temperature and the oxygen partial pressure. With an increase of the applied DC bias, the logarithm of the polarization resistance decreases linearly due to additional oxygen vacancies and the lowered chemical potential of oxygen at the BSCF/LSGM interface by the applied voltage. The exchange current density reaches to 182 mA cm⁻² at 700 °C, suggesting that the ORR kinetics at the BSCF/LSGM interface is high due to the excellent mixed ionic and electronic conductivity of BSCF.     

Investigation on scandium-doped manganate La0.8Sr0.2Mn1−xScxO3−δ cathode for intermediate temperaturesolid oxide fuel cells

Scandium-doped lanthanum strontium manganate La_0.8Sr_0.2Mn_1−xSc_xO_3−δ (LSMS) combined with YSZ as composite cathode for anode-supported solid oxide fuel cell is investigated. The LSMS powders are prepared using the modified Pechini method. The XRD and H₂-TPR results reveal that non-stoichiometric defects are introduced into the perovskite lattice of LSMS samples as a result of Sc substitution, which leads to increased oxygen ion mobility in the Sc containing samples. But high level doping of Sc may results in the segregation of the Sc₂O₃ secondary phase at elevated temperature. The cells with the LSMS-containing cathodes exhibit higher performances, especially at lower temperatures, which can be ascribed to the increased oxygen anionic vacancies in the LSMS.     

Palladium and ceria infiltrated La0.8Sr0.2Co0.5Fe0.5O3−δ cathodes of solid oxide fuel cells

La_0.8Sr_0.2Co_0.5Fe_0.5O_3−δ (LSCF) cathodes infiltrated with electrocatalytically active Pd and (Gd,Ce)O₂ (GDC) nanoparticles are investigated as high performance cathodes for the O₂ reduction reaction in intermediate temperature solid oxide fuel cells (IT-SOFCs). Incorporation of nano-sized Pd and GDC particles significantly reduces the electrode area specific resistance (ASR) as compared to the pure LSCF cathode; ASR is 0.1 Ω cm² for the reaction on a LSCF cathode infiltrated with 1.2 mg cm⁻² Pd and 0.06 Ω cm² on a LSCF cathode infiltrated with 1.5 mg cm⁻² GDC at 750 °C, which are all significantly smaller than 0.22 Ω cm² obtained for the reaction on a conventional LSCF cathode. The activation energy of GDC- and Pd-impregnated LSCF cathodes is 157 and 176 kJ mol⁻¹, respectively. The GDC-infiltrated LSCF cathode has a lower activation energy and higher electrocatalytic activity for the O₂ reduction reaction, showing promising potential for applications in IT-SOFCs.