In-situ construction and activities of La0·8Sr1·2Fe0·5Ni0·5O4+δ@CNTs hybrids as bifunctional oxygen catalysts

Abstract

Perovskite oxides are proved to be promising oxygen bifunctional catalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Constructing a perovskite oxide/carbon composite with intimate interaction at the interface is of great importance for conductivity and bifunctional oxygen activities. In this work, combining “exsolution effect” of perovskite oxide at high temperature and reducing atmosphere, carbon nanotubes (CNTs) are in-situ synthesized on the surface of a La0·8Sr1·2Fe0·5Ni0·5O4+δ (LSFN) perovskite oxide with K2NiF4 structure via a simple chemical vapor deposition (CVD) method. Physical characterizations show that CNTs are twining around the surface of LSFN particles with strong interaction. Under the function of synergistic effect between LSFN and CNTs, more mobile oxygen species, improved surface electronic structure and optimized charge distribution and transformation are obtained. Finally, the as-prepared LSFN@CNTs composites exhibit superior oxygen electrocatalytic performances in alkaline solution, with an ORR overpotential of 761 mV at −1.0 mA cm−2, a small OER overpotential of 314 mV at 10 mA cm−2 and an enhanced cycling stability of >3000 cycles, which outperforms commercial IrO2 catalyst and published perovskite oxide based bifunctional oxygen catalysts.