Rechargeable metal–air batteries and water splitting are highly competitive options for a sustainable energy future, but their commercialization is hindered by the absence of cost-effective, highly efficient and stable catalysts for the oxygen evolution reaction. Here we report the rational design and synthesis of a double perovskite PrBa0.5Sr0.5Co1.5Fe0.5O5+δ nanofiber as a highly efficient and robust catalyst for the oxygen evolution reaction. Co-doping of strontium and iron into PrBaCo2O5+δ is found to be very effective in enhancing intrinsic activity (normalized by the geometrical surface area, ∼4.7 times), as validated by electrochemical measurements and first-principles calculations. Further, the nanofiber morphology enhances its mass activity remarkably (by ∼20 times) as the diameter is reduced to ∼20 nm, attributed to the increased surface area and an unexpected intrinsic activity enhancement due possibly to a favourable eg electron filling associated with partial surface reduction, as unravelled from chemical titration and electron energy-loss spectroscopy.

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.

A multi-phase catalyst coating, composed of a thin-film PrBa 0.8 Ca 0.2 Co 2 O 5+d (PBCC) decorated with nanoparticles (NPs) of BaCoO 3Àx and PrCoO 3Àx , has dramatically enhanced the rate of oxygen reduction reaction. Oxygen molecules adsorb and dissociate rapidly on the NPs due to enriched surface oxygen vacancies, while the dissociated oxygen species transport quickly through the PBCC film into the cathode.

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A hybrid catalyst coating dramatically enhances the electrocatalytic activity and durability of a solid oxide fuel cell cathode.

PrBa0.8Ca0.2Co2O5+δ material has shown remarkable ORR activity and excellent CO2 tolerance, as confirmed by experimental and computational tools.

A class of double-perovskite compounds display fast oxygen ion diffusion and high catalytic activity toward oxygen reduction while maintaining excellent compatibility with the electrolyte. The astoundingly extended stability of NdBa(1-x)Ca(x)Co2O(5+δ) (NBCaCO) under both air and CO2-containing atmosphere is reported along with excellent electrochemical performance by only Ca doping into the A site of NdBaCo2O(5+δ) (NBCO). The enhanced stability can be ascribed to both the increased electron affinity of mobile oxygen species with Ca, determined through density functional theory calculations and the increased redox stability from the coulometric titration.

instability. [10] Very recently, 1D nanofiber cathode has shown both enhanced ORR activity and good thermal stability at the operating temperatures. [15][16][17] Moreover, such unique electrode architectures have the advantages of high porosity, good connectivity, and continuous pathway for charge and mass transport. [12,17,18] For example, a cathode composed of nanofibers of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF) and nanoparticles of Gd 0.1 Ce 0.9 O 2 (GDC) demonstrated a peak power density of about1.33 W cm −2 at 800 °C. [17] Further, the use of nanofibers in other work has also showed a reduction in polarization resistance or enhancement in cell performance. [19,20] However, the main concern is that the nanofibers/nanoparticles may not survive at the high operating temperature (750-800 °C) for a long period of time. Further, the nanofiber structure is hard to maintain when a ball-milling process is used for the preparation of electrode ink.In this communication, we report a unique cell design, consisting of a Ni-BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ (BZCYYb) anode, a GDC electrolyte, and an LSCF fiber cathode, to demonstrate a high-performance, low-temperature (LT)-SOFC. At 600 °C, the cell exhibits an OCV of 1.03 V, a peek power density of ≈0.62 W cm −2 , and a reliable long-term stable performance for 450 h at a constant voltage of 0.7 V when humidified H 2 (3 vol% water vapor) was used as fuel and ambient air as oxidant. Figure 1a schematically shows the fabrication of LSCF fiber mats by electrospinning the precursor solution of LSCF. The fiber mat shows a continuously connected fibrous network (Figure 1b), which was then fired at 950 °C and dispersed in acetone/V006 (mass ratio of 5:1), with a solid loading of 5 wt%. To fabricate a fiber-based cathode, 75 µL of the fiber slurry was then drop-coated on an electrolyte surface (in three times) using a syringe. Figure 1c shows some typical X-ray diffraction (XRD) patterns of a commercial LSCF powder and the LSCF fiber after firing in air at 800 °C for 2 h, suggesting that the phase of the LSCF fiber is similar to that of the commercial LSCF powder (no observable impurities). Figure 1d shows the typical transmission electron microscopy (TEM) images of the porous nanofibers after firing; the diameters of the fibers are ≈200 nm. It is also noted that the fibers are composed of LSCF nanoparticles with sizes of ≈50 nm and pores of ≈50 nm, as revealed by the Scanning Transmission Electron Microscope (STEM) image (inset). Figure 1e is an electron energy-loss spectroscopy (EELS) spectrum from a spot (≈1 nm in diameter) on the fiber in which peaks of O, Fe, Co, and La elements are clearly seen (Sr is out of the range). In addition, the EELS profile scanning (Figure 2f) from the red line in Figure 1d inset indicated a relatively uniform distribution of the elements in the LSCF nanofiber. The LSCF fiber we selected for SOFC cathode is the one generated by electrospinning LSCF precursor with concentration of Reducing the operating temperature of solid oxide fuel cells (SOFCs...