Designed synthesis of three-dimensional callistemon-like networks structural multifunctional electrocatalyst: Graphitic-carbon-encapsulated Co nanoparticles/N-doped carbon nanotubes@carbon nanofibers for Zn-air batteries application

Here, we successfully synthesize three-dimensional (3D) callistemon-like hierarchical networks structural catalysts (CoNC/NCNTs@CNF) in which Co nanoparticles are encapsulated within N-doped carbon nanotubes apexes via electrospinning method combined with two-step pyrolysis process. Benefiting from the unique 3D callistemon-like structure, CoNC/NCNTs@CNF affords adequate surface area (261 m2 g−1) and the enhanced electronic conductivity (even superior to Pt/C and RuO2). Due to the synergistic effect of the coupling between highly Co–N–C active sites and unique 3D callistemon-like structure, CoNC/NCNTs@CNF was explored as the trifunctional electrocatalysts for oxygen reduction reaction, oxygen evolution reaction, and hydrogen evolution reaction. Further, we assemble the catalysts as an air electrode for Zn-air batteries, demonstrating a maximum power density of 260 mW cm−2, and excellent cycling stability even after 43 h at 5 mA cm−2. Thus, this work offers a guide to the design of metal organic frameworks-derived 3D structure materials combined with electrospinning for wider application in renewable energy technologies.