Electrostatic Spinning Strategy to Prepare Cage-like PAN-Fiber Network-Wrapped Co–N–C Structures for the Oxygen Reduction Reaction

Abstract

Zeolitic imidazolate framework (ZIF)-derived carbon materials are highly desirable cathode catalysts for the oxygen reduction reaction (ORR). Unfortunately, ZIF-derived materials undergo microscale migration, structural collapse, and aggregation of Co atoms during high-temperature pyrolysis. Here, we used an electrospinning technique to combine polyacrylonitrile (PAN) with carbonized ZIF-67 that can obtain cage-like nanocomposite catalysts (Co–N–C@PAN) by repyrolysis. It is found that the obtained composite Co–N–C@PAN has a hierarchical structure, and a high surface area and pore space with a volume is favorable for the adequate disclosure of ORR active sites. More importantly, this cage-like structure forms a stable Co–N–C structure and allows Co nanoparticles to be uniformly found in the Co–N–C substrate, which improves the active site of Co–NX. The as-prepared samples exhibit superior performance for the ORR with an onset potential (Eonset) of 1.05 V versus the reversible hydrogen electrode (RHE) and a half-wave potential (E1/2) of 0.93 V versus the RHE, both of which are higher than commercial Pt/C. In addition, Co–N–C@PAN was applied as a cathode for zinc–air batteries and display a superior power density (132 mW cm–2) at a discharge current density of 219 mA cm–2. Furthermore, at a constant discharge current density of 10 mA cm–2, a specific capacity of 761 mA h gZn–1 was obtained. This study may provide an idea for the design and synthesis of nanostructures prepared by electrostatic spinning/ZIF composites.