Solid oxide fuel cells (SOFC) are the cleanest, most efficient, and cost-effective option for direct conversion to electricity of a wide variety of fuels. While significant progress has been made in anode materials with enhanced tolerance to coking and contaminant poisoning, cathodic polarization still contributes considerably to energy loss, more so at lower operating temperatures. Here we report a synergistic effect of co-doping in a cation-ordered double-perovskite material, PrBa0.5Sr0.5Co2−xFexO5+δ, which has created pore channels that dramatically enhance oxygen ion diffusion and surface oxygen exchange while maintaining excellent compatibility and stability under operating conditions. Test cells based on these cathode materials demonstrate peak power densities ~2.2 W cm−2 at 600°C, representing an important step toward commercially viable SOFC technologies.

The strontium effect in PrBa 1-x Sr x Co 2 O 5+δ (x = 0, 0.25, 0.5, 0.75, and 1.0) oxides was investigated based on their structural characteristics, electrical properties, and electrochemical performance. Electrical conductivities increase with increasing strontium content due to the higher oxygen content and coordination number. The area specific resistance (ASR) of PrBa 1-x Sr x Co 2 O 5+δ were measured on Ce 0.9 Gd 0.1 O 1.95 (GDC) and the minimum ASR values were observed at x = 0.5 and 0.75. Electrochemical performance of PrBa 1-x Sr x Co 2 O 5+δ cathodes was measured using Ni-GDC anode-supported cell. The maximum power density was 1.08 W cm −2 at 600 • C for x = 0.5 and 0.75.Fuel cells are gaining increasing recognition as a source of lowemission power generation. Solid oxide fuel cells (SOFCs) are promising energy conversion devices, offering an environmentally-friendly process, excellent fuel flexibility, and high efficiency among various fuel cells. Despite their many advantages, they require high operating temperature (>1000 • C), which causes degradation of cell components from high-temperature oxidation, corrosion, chemical inter-diffusion and reaction, and structural failure. 1-4 As a solution, intermediate temperature solid oxide fuel cells (IT-SOFCs) operating in a temperature range of 500-700 • C have been introduced, providing attractive properties such as high oxygen ion diffusivity and a high surface exchange coefficient. 5 The main obstacle impeding practical use of IT-SOFCs is the poor activity of traditional cathode materials for electrochemical reduction of oxygen. Therefore, the development of a new cathode material with high electro-catalytic activity could be a major step toward the commercialization of IT-SOFCs.The perovskite oxides, particularly mixed ionic/electronic conductors (MIECs) containing Mn, Fe, Co, and/or Ni, have been extensively investigated as IT-SOFC cathode materials. Cobalt-containing oxides such as Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ , Pr 1-x Sr x CoO 3 , Sm 0.5 Sr 0.5 CoO 3 , La 1-x Sr x Co 1-y Fe y O 3-δ , and Ba 0.6 La 0.4 CoO 3 have attracted much interest due to their high electro-catalytic activity for the oxygen reduction reaction (ORR) at the cathode. [5][6][7][8][9][10][11] Recently, many researchers have focused on layered perovskite oxides based on their much higher chemical diffusion and surface exchange coefficient relative to those of ABO 3 -type perovskite oxides. The layered perovskite oxides can be attributed with the general formula AA B 2 O 5+δ , with the A-site being a rare earth element, the A site an alkaline earth element, and the B-site a transition element. These oxides consist of sequential layers [BO 2 ]-[AO]-[BO 2 ]-[A O] stacked along the c-axis. 12 This layered structure reduces the oxygen bonding strength in the [AO] layerand provides a disorder-free channel for ion motion, which enhances oxygen diffusivity. 13 Based on these promising properties, several groups have studied the layered perovskite oxide LnBaCo 2 O 5+δ (LnBCo) (Ln=La, Pr...

Recently, a novel cathode material PrBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+d (PBSCF) has been proposed as a solution to overcome the drawbacks of a conventional cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Here we report systematic procedures to optimize the sintering temperature and the composite for PBSCF as an IT-SOFC cathode. For optimization of the heat treatment conditions for a PBSCF composite cathode, the effects of sintering temperature on the microstructure and electrical transport properties of the material are examined. We also suggest the optimization processes to effectively expand the electrochemical reaction zone based on a combination of a mixed ionic and electronic conductor (MIEC) electrode and an ionically conducting phase (PBSCF-Ce 0.9 Gd 0.1 O 1.95 (GDC)x, x ¼ 0, 20, 40, 50, and 60 wt%). The optimal intersection point between these two processing systems is revealed to be 50 wt% of GDC containing a composite cathode sintered at 950 C for 4 h. The area specific resistance (ASR) of PBSCF-GDC50 sintered at 950 C for 4 h reaches a minimum value of 0.052 U cm 2 at 600 C, which is consistent with the electrochemical performance results representing peak power density of $2.0 W cm À2 at 600 C.

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Layered perovskite oxides have received extensive attention as promising cathode materials for solid oxide fuel cells (SOFCs) because of their faster diffusion coefficient and oxygen transport kinetics. With the goals of enhancing electrochemical properties and improving the durability, this study focuses on the effect of calcium (Ca) doping in PrBa 0.5 Sr 0.5Àx Ca x Co 2 O 5+d (x ¼ 0 and 0.25) layered perovskite oxides through an investigation of their structural characteristics, electrical properties, redox behavior, electrochemical performances, and stability. In the temperature range of 100-750 C, the electrical conductivity of PrBa 0.5 Sr 0.25 Ca 0.25 Co 2 O 5+d (PBSCaCO) is higher than that of Ca-free PrBa 0.5 Sr 0.5 Co 2 O 5+d (PBSCO). The area specific resistance (ASR) value of PBSCaCO-GDC (0.079 U cm 2 ) is lower than that of PBSCO-GDC (0.093 U cm 2 ) at 600 C, based on a GDC electrolyte. Moreover, PBSCaCO-GDC achieves a good performance of 1.83 W cm À2 at 600 C. PBSCaCO shows a stable power output without observable degradation for 100 h. On the basis of these results, the PBSCaCO cathode is an excellent candidate for IT-SOFC applications.