Nanoscale Intertwined Biphase Nanofiber as Active and Durable Air Electrode for Solid Oxide Electrochemical Cells

We developed a novel and economical airelectrode for solidoxide cells, which is vital in zero carbon energy cycle. The poor temperature activity and durability due to surfaceSrsegregation are two main challenges restricting the practicabilityof state-of-the-art La1-x Sr x Co1-y Fe y O3 (LSCF) air electrodes for solidoxide electrochemical cells (SOCs). This article reports the recentdiscovery to unleash the constraints of performance and stabilityby constructing a novel nanofiber air electrode consisting of a LSCFhost and GDC guest in nanoscale intertwined moiety (LSCF/GDC NF).The electrical conductivity relaxation and distribution of relaxationtime results collectively disclosed the boosted surface oxygen exchangerate by two orders of magnitude at moderate SOC operation conditions(600 degrees C), as compared to commercial LSCF (1.01 x 10(-3) cm s(-1) vs 4.1 x 10(-5) cm s(-1)). As a result, the electrochemical performancewas synchronically promoted by over 5-fold (0.12 omega center dot cm(2) vs 0.64 omega center dot cm(2)). Moreover, the intervalstability test over 200 h in switching atmospheres (air/H2O/CO2) buttresses the superb robustness of LSCF/GDC NFwith an extremely slow deactivation rate of 1.79 x 10(-6) omega center dot cm(2) h(-1) and nondetectabletop-surface Sr segregation, collectively affirmed by X-ray photoelectronspectroscopy and low-energy ion scattering spectra. At atomic scale,the operando X-ray diffraction results preliminarily unravel thatthe formation of intertwined moiety employs the compressive strainon LSCF, which maintains the length of Sr-O against thermoinducedelongation. In addition, systemically, XPS and density functionaltheory simulation results prove the thermodynamically favored formationof oxygen vacancies at the biphase boundary in LSCF/GDC NF and raisedthe energy barrier for the formation of an intrinsic vacant Sr site.This study provides a practical and facile strategy to engineer theair electrode with enhanced performance and durability.