Bead-Structured Triple-Doped Carbon Nanocage/Carbon Nanofiber Composite as a Bifunctional Oxygen Electrocatalyst for Zn–Air Batteries

Zeolitic imidazolate framework (ZIF)-derived metal–nitrogen carbon (M–N–C) materials are considered as promising electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) applied in rechargeable zinc–air batteries (ZABs). However, due to their unsatisfied conductivity and aggregation, appropriate regulations about structure and components are still necessary to achieve superior bifunctional performance. Herein, by simple ion exchange and one-step electrospinning method, a beaded composite electrocatalyst (Fe, Co–N–C/CNF) with Fe, Co, N codoped carbon nanocages uniformly embedded in the carbon nanofibers one by one was synthesized, achieving simultaneous structural and compositional regulation. Benefiting from the beaded-like structure and dual sites, the Fe, Co–N–C/CNF exhibits outstanding bifunctional catalytic performance for the ORR and the OER. Ultraviolet photoelectron spectroscopy (UPS) reveals that Fe, Co–N–C/CNF has a low electron transfer barrier between active centers and the ORR (OER) intermediates, ultimately accelerating the reaction kinetics. In addition, the Fe, Co–N–C/CNF-based ZAB also demonstrates superior charge–discharge performance compared to the Pt/C-RuO2-based ZAB. This study not only offers an effective structural design strategy but also provides a component regulation method for ZIF-derived materials as bifunctional electrocatalysts.