Interface engineering of an electrospun nanofiber-based composite cathode for intermediate-temperature solid oxide fuel cells

Sluggish oxygen reduction reaction(ORR)kinetics are a major obstacle to developing intermediate-temperature solid-oxide fuel cells(IT-SOFCs).In particular,engineering the anion defect concentration at an interface between the cathode and electrolyte is important for facilitating ORR kinetics and hence improving the electrochemical performance.We developed the yttria-stabilized zirconia(YSZ)nanofiber(NF)-based composite cathode,where the oxygen vacancy concentration is controlled by varying the dopant cation(Y2O3)ratio in the YSZ NFs.The composite cathode with the optimized oxygen vacancy concentration exhibits maximum power densities of 2.66 and 1.51 W cm^(−2)at 700 and 600℃,respectively,with excellent thermal stability at 700℃ over 500 h under 1.0 A cm^(−2).Electrochemical impedance spectroscopy and distribution of relaxation time analysis revealed that the high oxygen vacancy concentration in the NF-based scaffold facilitates the charge transfer and incorporation reaction occurred at the interfaces between the cathode and electrolyte.Our results demonstrate the high feasibility and potential of interface engineering for achieving IT-SOFCs with higher performance and stability.

A High Dielectric N-Type Small Molecular Acceptor Containing Oligoethyleneglycol Side-Chains for Organic Solar Cellst

We report a new small molecular acceptor, ITIC-OEG, which is based on indacenodithieno[3,2-b]thiophene and 1,1-（dicyanomethylene）-3- indanone including oligoethyleneglycol （OEG） side-chains. ITIC-OEG was found to have higher dielectric constant （ε1=5.6} than that of a reference molecule of ITIC with normal alkyl substituents （ε1=3.9）. The dielectric constant of medium influences significantly the exciton binding energy and the resulting charge separation and recombination. The optical, electrochemical and morphological properties of ITIC-OEG and its photovoltaic characteristics were investigated by blending with a semi-crystalline donor polymer, PPDT2FBT, with comparison to those of ITIC. ITIC-OEG shows more red-shifted absorption and stronger crystalline packing than ITIC. However, the lower photovoltaic performance （with 1.58% power conversion efficiency, PCE） was measured for PPDT2FBT-ITIC-OEG, compared to PPDT2FBT：ITIC （5..52% PCE）. The incompatibility between PPDT2FBT and ITIC-OEG （due to high hydrophilic nature of OEG chains） resulted in poor intermixing with large domain separation over 300 nm, showing inefficient charge separation and significant charge recombination. Therefore, to investigate the effect of dielectric constant of the materials on the charge separation and recombination, the blend morphology of the PPDT2FBT：ITIC-OEG should be optimized first by improving their miscibility and phase separation.