IT-SOFC Cathode Research Articles

Temperature-controlled in-situ construction of composition-tunable nanoparticle-decorated SOFC cathodes with enhanced oxygen reduction kinetics and CO2 tolerance

High oxygen reduction reaction (ORR) catalytic activity and CO2 resistance of the cathode are fundamental to the commercial application of solid oxide fuel cells (SOFCs). Therefore, we develop a temperature-driven reduction-reoxidation strategy to in-situ construct heterostructured perovskite cathodes decorated with different nanoparticles by controlling the reduction temperature. For (Pr0.4Sr0.6)0.95Co0.2Fe0.8-xNixO3-δ (PSCFN, x = 0.05, 0.1), reduction (@700 °C)-reoxidation results in the exsolution of a ComFenNi3-m-nO4 spinel phase on the perovskite scaffold surface, while reduction (@750 °C)-reoxidation leads to the formation of both ComFenNi3-m-nO4 spinel phase and NiO nanoparticles. The exsolution of these highly active species increases the quantity of oxygen reduction active sites and effectively suppresses Sr segregation. The simultaneous formation of ComFenNi3-m-nO4 spinel phase and NiO nanoparticles induces B-site ion vacancies in the main phase, therefore facilitates the formation of oxygen vacancies. Additionally, the presence of ComFenNi3-m-nO4/NiO/PSCFN heterointerfaces promotes oxygen adsorption and transfer. The strong interactions among ComFenNi3-m-nO4, NiO, and PSCFN significantly enhance the structural stability. At 800 °C, Reo2-PSCFN0.1 achieves an output performance of 1.12 W cm−2, representing a 36.6 % enhancement compared to PSCFN0.1. Moreover, the Rp of Reo2-PSCFN0.1 is merely 0.0186 Ω cm2, marking a 40.4 % decrease relative to PSCFN0.1. This temperature-driven reduction-reoxidation strategy shows great promise as a novel approach for creating high-performance IT-SOFC cathodes.

A tutorial review on solid oxide fuel cells: fundamentals, materials, and applications

AbstractSolid oxide fuel cells (SOFCs) are recognized as a clean energy source that, unlike internal combustion engines, produces no CO2 during operation when H2 is used as a fuel. They use a highly efficient chemical-to-electrical energy conversion process to convert oxygen and hydrogen into electricity and water. They can provide smaller-scale power for transportation (e.g., cars, buses, and ships) and be scaled up to provide long-term energy for an electrical grid, making SOFCs a promising, clean alternative to hydrocarbon combustion. Conventional SOFCs faced challenges of high operating temperatures, high cost, and poor durability. Research into advanced cathode, anode, electrolyte, and interconnect materials is providing more insight into the ideal structural and chemical properties that enable the commercialization of highly stable and efficient intermediate temperature (IT) SOFCs. In this paper, we discuss the functional properties of the cathode, anode, electrolyte, and interconnectors for IT-SOFCs. The performance of SOFCs depends not only on the materials used but also on the optimization of operating conditions to maximize efficiency. The voltaic, thermodynamic, and fuel efficiency of SOFCs is presented.

Recent Advances in Barium Cobaltite-Based Perovskite Oxides as Cathodes for Intermediate-Temperature Solid Oxide Fuel Cells.

Solid oxide fuel cells (SOFCs) are considered as advanced energy conversion technologies due to the high efficiency, fuel flexibility, and all-solid structure. Nevertheless, their widespread applications are strongly hindered by the high operational temperatures, limited material selection choices, inferior long-term stability, and relatively high costs. Therefore, reducing operational temperatures of SOFCs to intermediate-temperature (IT, 500-800°C) range can remarkably promote the practical applications by enabling the use of low-cost materials and enhancing the cell stability. Nevertheless, the conventional cathodes for high-temperature SOFCs display inferior electrocatalytic activity for oxygen reduction reaction (ORR) at reduced temperatures. Barium cobaltite (BaCoO3-δ)-based perovskite oxides are regarded as promising cathodes for IT-SOFCs because of the high free lattice volume and large oxygen vacancy content. However, BaCoO3-δ-based perovskite oxides suffer from poor structural stability, inferior thermal compatibility, and insufficient ionic conductivity. Herein, an in-time review about the recent advances in BaCoO3-δ-based cathodes for IT-SOFCs is presented by emphasizing the material design strategies including functional/selectively doping, deficiency control, and (nano)composite construction to enhance the ORR activity/durability and thermal compatibility. Finally, the currently existed challenges and future research trends are presented. This review will provide valuable insights for the development of BaCoO3-δ-based electrocatalysts for various energy conversion/storage technologies.

A novel Co-free and efficient Pr0.5Ba0.5Fe0.8Cu0.2O3-δ nanofiber cathode material for intermediate temperature solid oxide fuel cells

Fe-based perovskite without Co has a low thermal expansion coefficient and can be used as a solid oxide fuel cell (SOFC) cathode to ensure the thermal compatibility with the electrolyte; however, its further advancement is impeded by sluggish oxygen reduction reaction (ORR) dynamics. In this work, the electrospinning method and Cu doping strategy are employed to improve the microstructure and oxygen reduction kinetics of Pr0.5Ba0.5FeO3-δ cathodes. The results show that Pr0.5Ba0.5Fe0.8Cu0.2O3-δ has a unique fiber structure and high specific surface area, and the introduction of Cu facilitates the release of lattice oxygen, effectively increasing the oxygen vacancy content. The relaxation time distribution analysis and oxygen reduction reaction dynamics indicate that the oxygen adsorption-dissociation process is the main rate-limiting step in the oxygen reduction reaction of Pr0.5Ba0.5Fe0.8Cu0.2O3-δ electrode materials. At 700 °C, the area-specific resistance (ASR) of the symmetric cell of Pr0.5Ba0.5Fe0.8Cu0.2O3-δ fiber material is 0.071 Ω cm2, and the power density of the single cell reaches 988 mW cm−2, which shows good electrochemical output performance and long-term operational stability. The preparation of nanofiber cathodes with high specific surface area and porosity by electrospinning provides an effective strategy to enhance the electrocatalytic activity of the IT-SOFC cathode.

Preparation of high-performance multiphase heterostructures IT-SOFC cathode materials by Pr-induced in situ assembly

Here, in situ assembly in La0.6Sr0.4Co0.2Fe0.8O3-δ and CoFe2O4 composite (LSCFC) cathode was induced by Pr to form La0.6Sr0.4CoxFeyO3-δ/PrCoO3/Co3O4/PrO2 (LSCFC-PI) multiphase heterostructures. The surface of LSCFC-PI forms uniform nanoparticles, and the unique core-shell structure prevents Sr segregation, thereby enhancing CO2 tolerance and increasing oxygen reduction reaction (ORR) active sites. Furthermore, compared with LSCFC, LSCFC-PI increases the oxygen vacancy content of the cathode due to the existence of multiphase heterostructure, improves the ORR kinetics, and the conductivity is also greatly improved. The peak power density (PPD) of LSCFC-PI as a single-cell cathode at 700 ℃ reached 1.51 W cm−2, which was 2.65 times higher than that of LSCFC's 0.57 W cm−2, and in the long-term stability test at a constant voltage ∼0.8 V for 100 hours, showing excellent stability. In situ assembly of multiphase heterostructures is expected to become a new strategy for developing high-performance IT-SOFC cathodes.

Evaluation of highly conductive cermet cathodes synthesized with organic chelating agents and sintered at low temperatures for IT-SOFCs

A novel semi-organic combustion approach using orange and lemon juice as chelating agents is employed to synthesize the perovskite Sr0.8X0.2Co0.2Fe0.8O3-δ (x = La, Ce) cathode for IT-SOFCs. This approach has been found to exhibit lower toxicity compared to chemical routes and lower impurities compared to green routes. The structural analysis validated the successful synthesis of perovskite Sr0.8X0.2Co0.2Fe0.8O3-δ (La, Ce) cathode materials with no prominent secondary phase of impurities while surface morphology revealed a porous and well-connected network of particles. EDS confirmed the composition and thermo-gravimetric analysis showed weight losses related to the creation of vacancies. The functional groups were investigated through FTIR and the conductivity measurements revealed higher electrical conductivity for Sr0.8X0.2Co0.2Fe0.8O3-δ (x = La, Ce) synthesized with orange juice as a chelating agent with Sr0.8La0.2Co0.2Fe0.8O3-δ exhibiting slightly higher value compared to Sr0.8Ce0.2Co0.2Fe0.8O3-δ. The electrochemical performance showed the highest power density of 354 and 313 mW·cm−2 at 700 °C obtained for cells having Sr0.8X0.2Co0.2Fe0.8O3-δ (x = La, Ce) cathodes synthesized with orange juice which was attributed to better crystallinity and uniform lattice. This work shows that a novel semi-organic route is successfully employed to synthesize the perovskite cathode materials for IT-SOFCs.

High performance of SrCo1-xZrxO3-δ perovskite cathodes for IT-SOFCs

Stabilization of a tetragonal perovskite structure in the SrCoO3-δ system at room temperature has been achieved through wet chemical techniques, and it has been successfully tested in Solid Oxide Fuel Cells (SOFCs). Chemical substitutions at the Co position were carried out by introducing different amounts of zirconium (SrCo1-xZrxO3−δ; x = 0.05, 0.08 and 0.11) to destabilize the columns of CoO6 octahedra sharing faces in the competitive 2H-hexagonal phase. The crystal structure was studied by X-ray diffraction (XRD) and neutron powder diffraction (NPD) at 25 °C and correlated with mechanical and electrical properties. Chemical compatibility studies between the samples and the La0.8Sr0.2Ga0.83Mg0.17O3-δ (LSGM) electrolyte revealed not interaction at high temperatures. Dilatometric analysis measurements showed a compatible thermal expansion with the LSGM electrolyte over the entire temperature range, demonstrating good mechanical compatibility. Furthermore, the relatively high conductivity values (∼83 S cm-1 at 850 °C) indicated their suitability as cathodes in SOFCs. Finally, test cells prepared with an electrolyte (LSGM) supported configuration provided a maximum output power exceeding 600 mW/cm2 using pure H2 as fuel at 850 °C. Importantly, the performance of the cathode materials did not degrade after extended operation at this temperature.

Fabrication and performance investigation of high entropy perovskite (Sr0.2Ba0.2Bi0.2La0.2Pr0.2)FeO3 IT-SOFC cathode material

The high-entropy oxide (HEO) concept expands the design space of solid oxide fuel cell (SOFC) cathode materials. There is great potential for the development of HEO cathode materials that has not been fully explored, and the relationship between their chemical composition, grain size, and electrochemical performance is not yet fully understood. This experimental design involved the preparation of single-phase perovskite (Sr0.2Ba0.2Bi0.2La0.2Pr0.2)FeO3 HEO SOFC cathode materials, and we systematically studied the effects of synthesis temperature and microstructure on their electrochemical performance. The results show that as the synthesis temperature increases, structural transformations from multiphase to single-phase perovskite HEO can be observed. It exhibits excellent conductivity and electrochemical performance (the minimum polarization resistance reaches 0.033 Ω∙cm2, and the maximum power density is 664 mW∙cm−2). The single-phase perovskite HEO sample exhibits higher electrochemical performances compared to those of multiphase perovskite. Furthermore, it exhibits outstanding ability to suppress Sr segregation, chemical compatibility with Ce0.8Sm0.2O1.9(SDC), and CO2 tolerance performance. The Distribution of relaxation time(DRT) analysis shows that as the synthesis temperature (1000–1150 ℃) increase, HEO single-phase formed and the oxygen atom reduction ability of the SBBLP samples was improved; and the adsorption of gas oxygen on the electrode surface is limited with porosity decreases. The work shows it is interesting and valuable to optimize the performance of SOFC cathode materials using a high entropy design.

Increasing thermodynamic stability and electrochemical performance of IT-SOFC cathodes based on Ln2MO4 (Ln = La, Pr; M = Ni, Cu)

La2-xPrxNi1-yCuyO4+δ (x = 0.5, 1, 1.5, y = 0.4, 0.6, 0.8) were synthesized by a citrate-nitrate method and studied as cathode materials for IT-SOFCs by Electrochemical Impedance Spectroscopy (EIS) in symmetrical cells based on the Ce0.8Sm0.2O2-δ (SDC) and La28-zW4+zO54+1.5z (z = 0.85, LWO) electrolytes. Phase identification and crystal structure analysis by means of X-ray powder diffraction (XRPD) shows that solubility of copper y decreases with the increase in praseodymium content x due to increasing structural distortions. Thermodynamic stability of La2-xPrxNi1-yCuyO4+δ at intermediate temperatures in air tends to decrease with praseodymium doping level x and increases with copper substitution for nickel y. Oxides with x = 0.5 and 0.6≤y ≤ 0.8 are shown to be thermodynamically stable at 700 °C in air. Electrochemical performance of the La2-xPrxNi1-yCuyO4+δ electrodes improves with praseodymium and copper doping. The results of EIS measurements at different temperatures and oxygen partial pressures (P(O2)) reveal that the rate-determining step of the overall electrochemical process is charge transfer, which can be a combination of surface diffusion and bulk diffusion. EIS studies in dry and wet air indicate the presence of proton conduction in the studied electrodes. The area-specific resistances (ASRs) for La2-xPrxNi1-yCuyO4+δ with x = 0.5, y = 0.6 and y = 0.8 in contact with SDC are comparable with those reported for Pr2NiO4+δ and equal to 0.07 and 0.065 Ω cm2 at 800 °C.

An acidity-regulated double perovskite cathode for efficient and durable power generation of intermediate-temperature solid oxide fuel cells

This work reports a double perovskite oxide EuBa0.5Sr0.5Co2−xFexO5+δ (EBSCFx, x = 0.5, 1, and 1.5) as cathode for IT-SOFC. Specifically, the cell using EBSCF1.0 cathode delivers excellent performance with a PPD of 1.50 W cm−2 at 650 °C.

Tuning the ORR catalytic activity of LaFeO3-δ-based perovskite cathode for solid oxide fuel cells by doping with alkaline-earth metal elements

Co-based perovskite cathodes have demonstrated impressive catalytic activity for oxygen reduction reaction (ORR) at intermediate temperatures. However, these cathodes face the challenges such as high cost and thermal expansion coefficient (TEC) mismatch. On the other hand, Fe-based perovskite oxides like LaFeO3 exhibit more stable properties and lower TEC, but their ORR activity is not as remarkable as that of Co-based cathodes. In this study, La3+ at the A-site of LaFeO3 was substituted by aliovalent alkaline-earth metal cations. The research findings reveal that the doping of alkaline-earth metal ions induces the formation of structural defects and alters the valence state of Fe. This leads to an increase in the conductivity and oxygen vacancy concentration, which are critical for ORR kinetics in both H–SOFC and O–SOFC. Among the various dopants, Sr doped LaFeO3 (LSrF) exhibits the most outstanding ORR catalytic activity. This can be attributed to its highest total conductivity, O2− conductivity, oxygen surface exchange coefficient, and oxygen bulk diffusion coefficient. At 700 °C, single cell with LSrF cathode achieves peak power densities of 0.781 and 0.894 W cm−2, for O2--conducting solid oxide fuel cell (SOFC) and H+-conducting SOFC, respectively. These performances are essentially twice that of single cell with LaFeO3 cathode. The findings of this study provide valuable insights into doping strategies for Fe-based perovskite cathodes and contribute to the advancement of IT-SOFC cathode research.

Sc-doped Co-based perovskites as IT-SOFC cathode with high oxygen reduction reaction and CO2 tolerance

The development of cathode materials with high oxygen reduction reaction (ORR) activity and stability in intermediate temperature (IT) environments is a key factor in the commercialization of solid oxide fuel cells (SOFC). In this paper, the ORR activity of the cathode is improved by doping high-valent Sc3+ ions at the B-site of the Sr0.5La0.5Co0.8Cu0.2-xScxO3–δ (x = 0, 0.02, 0.04), in which Sr0.5La0.5Co0.8Cu0.18Sc0.02O3–δ (SLCCS2) shows the best electrochemical performance, and the area-specific resistance of SLCCS2 at 700 °C is only 0.047 Ω cm2, much lower than the 0.087 Ω cm2 of Sr0.5La0.5Co0.8Cu0.2O3–δ (SLCC), and the peak power density of SLCCS2 reached 1.098 W cm−2, which is 1.84 times that of SLCC (0.598 W cm−2). In addition, SLCCS2 effectively reduces the thermal expansion coefficient, improves thermal matching with traditional electrolytes, and overcomes the problem of insufficient long-term SOFC stability caused by the high thermal expansion coefficient of Co-based perovskite to a certain extent. SLCCS2 also exhibits excellent CO2 tolerance. Considering comprehensively, SLCCS2 is expected to become an IT-SOFC cathode material with development potential.

Electrochemical investigation of Pr6O11 infiltration into La0.8Sr0.2MnO3-δ-Ce0.9Gd0.1O1.95 cathodes for IT-SOFC

Infiltration through spray-pyrolysis deposition is a one-step and effective method for enhancing the electrode performance of solid oxide fuel cells (SOFCs) at intermediate temperatures. Among various infiltrated electrodes, Pr6O11 has shown promising electrocatalytic properties for oxygen reduction reaction (ORR), despite its relatively low electrical conductivity. This study focuses on obtaining Pr6O11-infiltrated cathodes using spray-pyrolysis deposition, with different porous backbone layers that exhibit electronic and/or ionic conductivity: La0.8Sr0.2MnO3-δ (LSM), Ce0.9Gd0.1O1.95 (CGO), and LSM-CGO composite. The electrochemical properties and the subprocesses involved in the ORR are investigated in symmetrical cells. It is observed that the polarization resistance (Rp) decreases when the backbone layer exhibits high ionic conductivity. At 650 °C, the Rp values are 0.03, 0.06 and 0.1 Ω cm2 for CGO, LSM-CGO and LSM backbones, respectively. The dependence of Rp contributions with pO2 reveals that the same electrochemical processes are involved regardless of the backbone composition, confirming a less resistive oxide-ion transport from the TPB into the electrolyte with the CGO backbone. In contrast, the CGO backbone exhibits higher series resistance (Rs) (44.5 Ω cm), attributed to an increased contribution of ohmic losses compared to the LSM backbone (39.8 Ω cm). This study provides valuable insights into the performance and optimization of Pr6O11-infiltrated cathodes with different backbone compositions for their implementation in SOFCs.

Generation of nanoflowers and nanoneedles on Co-based layered perovskite of IT-SOFC cathode affecting electrical conductivities

In this study, the unusual microstructure and electrical properties of SmBa0.5Sr0.5Co2O5+d (SBSCO) layered perovskite cathodes with dense and porous microstructures were analyzed by changing the applied current.Unique nanostructure shapes were observed when a high current was applied to a cathode with both dense and porous microstructures of the same chemical composition for electrical conductivity measurement. Nanoflower and nanoneedles, which are types of nanoseeds, were discovered. The nanoneedles were found on the entire surface of the SBSCO cathode, whereas nanoflowers were only present on part of the cathode surface.Results from an Energy Dispersive Spectrometer (EDS) analysis revealed that the nanoneedles generated on the SBSCO matrix had a chemical composition of SmBaCo2O5+d (SBCO).The electrical conductivity of the porous cathode with SBCO nanoneedles (nanoneedle cathode) was 238 S/cm at 700 °C under decreasing temperature in an air atmosphere (Air Down) during the experiment. In comparison, the electrical conductivity of the porous cathode without nanoneedles (normal cathode) was 136 S/cm at the same experiment condition (700 °C, Air Down). This indicates that the electrical conductivity of the nanoneedle cathode was significantly higher than that of the normal cathode.

Electrochemical characteristic of non-stoichiometric SmBa0.45Sr0.5Co2O5+d layered perovskite oxide system for IT-SOFC cathode

In this study, the composition of the layered perovskite SmBa0.5Sr0.5Co2O5+d was changed to different non-stoichiometric compositions by changing the substitution amount of Ba and Sr.SmBa0.45Sr0.5Co2O5+d (SBSCO-0.45/0.5) showed the lowest area specific resistance (ASR) because the area % caused by high binding energy (HBE) of O1s in the X-ray photoelectron spectroscopy (XPS) analysis was the largest compared to all other tested compositions and also the unit cell volume was smaller than that of other samples.The dense SmBa0.5Sr0.48Co2O5+d (SBSCO-0.5/0.48) showed the highest electrical conductivity. This is because SBSCO-0.5/0.48 has the smallest decrease in oxygen contents compared to other samples when subject to temperature increase. Also, through XPS analysis, it was found that the area % of the Co3+ and Co4+ coexistence regions of Co2p of SBSCO-0.5/0.48 was the largest. The electrical conductivity values and behaviors of the porous SBSCO-0.45/0.5 and SBSCO-0.5/0.48 were not significantly different.Comparing the single-cell performance with composite cathodes comprised of SBSCO-0.45/0.5 and SBSCO-0.5/0.48 with CGO91, the results show that the single-cell with the SBSCO-0.45/0.5 and CGO91 cathode showed higher maximum power density.

Self-assembled cathode induced by polarization for high-performance solid oxide fuel cell

Herein, we developed an unsintered LaCo0.6Ni0.4O3−δ-Er0.4Bi1.6O3 cathode for IT-SOFC. The cathode/electrolyte interface is induced via polarization, and competitive performance is achieved.

Effect of Infiltration Ce0.8Sm0.2O1.9 Against Double Perovskite Performance LaBa0.5Sr0.5Co2O5+δ as IT-SOFC Cathode

Modifying the sample surface by infiltration technique using Ce0.8Sm0.2O1.9 (SDC) electrolyte has been done to increase the catalytic activity of the LaBa0.5Sr0.5Co2O5+δ (LBSC) cathode. The cathode powder structure was evaluated using X-ray diffraction (XRD) at room temperature, and the LBSC cathode microstructure was analyzed using scanning electron microscopy (SEM). The electrical conductivity of the LBSC cathode was tested using the four-probe DC method. Symmetrical cells were tested using a potentiostat Voltalab PGZ 301 and a digital source meter Keithley 2420. LBSC powder was discovered to have a tetragonal structure (space group: P4/mmm) with lattice parameters of a = 3.86253 Å, c = 7.73438 Å, and V = 115.338 Å. From the SEM image, the LBSC cathode has homogeneous, dense, and highly porous grains. The electrical conductivity showed metallic behavior, gradually decreasing from 167 S.cm-1 at 300℃ to 105 S.cm-1 at 800℃. A significant increase in current density (io) of 275% occurred at 800℃ from 154.10 mA.cm−2 (pure LBSC) to 577.86 mA.cm−2 (LBSC+0.5M SDC). The activation energy value (Ea) of symmetrical cells was determined using electrochemical impedance spectroscopy (EIS), low-field (LF), and high-field (HF) techniques. The activation energy of the LBSC+0.5 M SDC specimen was 47.9 kJ mol-1 or 79.4% lower than the activation energy of the LBSC cathode specimen without infiltration at atmospheric pressure of 0.03 atm. These results indicate that SDC infiltration of the LBSC cathode can reduce the activation energy of the significant. The cathode membrane adheres quite well to the electrolyte membrane, the cathode porosity varies in the range of 1–4 µm, and the grain size is 0.1–1.5 µm.

Development of La1.7Ca0.3Ni1-yCuyO4+δ Materials for Oxygen Permeation Membranes and Cathodes for Intermediate-Temperature Solid Oxide Fuel Cells.

The La1.7Ca0.3Ni1-yCuyO4+δ (y = 0.0-0.4) nickelates, synthesized via a solid-state reaction method, are investigated as prospective materials for oxygen permeation membranes and IT-SOFC cathodes. The obtained oxides are single-phase and possess a tetragonal structure (I4/mmm sp. gr.). The unit cell parameter c and the cell volume increase with Cu-substitution. The interstitial oxygen content and total conductivity decrease with Cu-substitution. The low concentration of mobile interstitial oxygen ions results in a limited oxygen permeability of Cu-substituted La1.7Ca0.3NiO4+δ ceramic membranes. However, increasing the Cu content over y = 0.2 induces two beneficial effects: enhancement of the electrochemical activity of the La1.7Ca0.3Ni1-yCuyO4+δ (y = 0.0; 0.2; 0.4) electrodes and decreasing the sintering temperature from 1200 °C to 900 °C. Enhanced electrode activity is due to better sintering properties of the developed materials ensuring excellent adhesion and facilitating the charge transfer at the electrode/electrolyte interface and, probably, faster oxygen exchange in Cu-rich materials. The polarization resistance of the La1.7Ca0.3Ni1.6Cu0.4O4+δ electrode on the Ce0.8Sm0.2O1.9 electrolyte is as low as 0.15 Ω cm2 and 1.95 Ω cm2 at 850 °C and 700 °C in air, respectively. The results of the present work demonstrate that the developed La1.7Ca0.3Ni0.6Cu0.4O4+δ-based electrode can be considered as a potential cathode for intermediate-temperature solid oxide fuel cells.

Enhanced Performance of La0.8Sr0.2FeO3-δ-Gd0.2Ce0.8O2-δ Cathode for Solid Oxide Fuel Cells by Surface Modification with BaCO3 Nanoparticles.

Recently, Fe-based perovskite oxides, such as Ln1-xSrxFeO3-δ (Ln = La, Pr, Nd, Sm, Eu) have been proposed as potential alternative electrode materials for solid oxide fuel cells (SOFCs), due to their good phase stability, electrocatalytic activity, and low cost. This work presents the catalytic effect of BaCO3 nanoparticles modified on a cobalt-free La0.8Sr0.2FeO3-δ-Gd0.2Ce0.8O2-δ (LSF-GDC) composite cathode at an intermediate-temperature (IT)-SOFC. An electrochemical conductivity relaxation investigation (ECR) shows that the Kchem value of the modified LSF-GDC improves up to a factor of 17.47, demonstrating that the oxygen reduction process is effectively enhanced after surface impregnation by BaCO3. The area-specific resistance (ASR) of the LSF-GDC cathode, modified with 9.12 wt.% BaCO3, is 0.1 Ω.cm2 at 750 °C, which is about 2.2 times lower than that of the bare cathode (0.22 Ω.cm2). As a result, the anode-supported single cells, with the modified LSF-GDC cathode, deliver a high peak power density of 993 mW/cm2 at 750 °C, about 39.5% higher than that of the bare cell (712 mW/cm2). The single cells based on the modified cathode also displayed good performance stability for about 100 h at 700 °C. This study demonstrates the effectiveness of BaCO3 nanoparticles for improving the performance of IT-SOFC cathode materials.

Evaluation of Nd0.8-x Sr0.2Ca x CoO3-δ (x = 0, 0.05, 0.1, 0.15, 0.2) as a cathode material for intermediate-temperature solid oxide fuel cells.

A series of Nd0.8−xSr0.2CaxCoO3−δ(x = 0, 0.05, 0.1, 0.15, 0.2) cathode materials was synthesized by sol–gel method. The effect of Ca doping amount on the structure was examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), thermal expansion, and X-ray photoelectron spectroscopy (XPS). Electrochemical properties were evaluated for possible application in solid oxide fuel cell (SOFC) cathodes. Results showed that second phase NdCaCoO4+δ is generated when the Ca doping amount is higher than 0.1. The increase in Ca limits the electronic compensation capacity of the material, resulting in a decrease in thermal expansion coefficient (TEC). With the increase of Ca content, the conductivity increases at first and then decreases, and the highest value of 443 S cm−1 is at x = 0.1 and T = 800 °C. Nd0.7Sr0.2Ca0.1CoO3−δ exhibits the lowest area specific resistance of 0.0976 Ω cm2 at 800 °C. The maximum power density of Nd0.7Sr0.2Ca0.1CoO3−δ at 800 °C is 409.31 mW cm−2. The Ca-doped material maintains good electrochemical properties under the coefficient of thermal expansion (CTE) reduction and thus can be used as an intermediate-temperature SOFC (IT-SOFC) cathode.