Effect of surface bonding of FePC with electrospun carbon nanofiber on electrocatalytic performance for aprotic Li-O₂...

The bifunctional catalysts assist the complete reversible cycle of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) with low polarization of a lithium-oxygen (Li-O₂) battery were known to be critical cathode components. In this work, electrospun nitrogen-doped carbon nanofibers (N-CNFs) were prepared to use as supports to anchor iron phthalocyanine (FePc) bifunctional catalyst for oxygen (O₂) electrode in Li-O₂ batteries. By using FePc and N-CNFs, two different bonding composites were fabricated via diazonium reaction by refluxing and physical mixing methods which were resulting into covalent linkage via pyridine (Py) (denoted as FePc/Py/N-CNFs) and noncovalent interaction via π-π stacking (denoted as FePc/N-CNFs). The systematic characterizations confirmed that the spun carbon nanofibers were functionalized by pyridine and the anchored FePc molecule donated the axial ligand for the iron (Fe) center in the FePc/Py/N-CNFs composite. The FePc were embedded in the N-CNFs composites combining the electrocatalytic activity of the FePc with ORR/OER processes and N-CNFs with a three-dimensional (3D) interconnected porous network structure through a connecting link of one-dimensional (1D) porous and N-doping carbon nanofiber which exhibited a high performance when acting as the cathode in Li-O₂ batteries. However, the FePc/Py/N-CNFs composite showed the higher catalytic activity and prominent structural stability due to the FePc being strongly interlinked with the N-CNFs through the Py connection, which could avoid the deformation and agglomeration of FePC molecules during cycling and thus possessed the high electrochemical performance of the composite. This study demonstrated the unique design of FePc/Py/N-CNFs composite structure in this work would be found as a promising O₂ electrode material with enhanced electrochemical performance in rechargeable Li-O₂ batteries.