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...
