Oxygen Engineering Enables N-Doped Porous Carbon Nanofibers as Oxygen Reduction/Evolution Reaction Electrocatalysts for Flexible Zinc-Air Batteries

Controllable designing of heteroatom-doped carboncatalysts provides an insightful strategy for boosting the perform-ance and kinetics of the oxygen reduction/evolution reaction(ORR/OER). However, the role of oxygen species is usuallyomitted. Herein, a facile oxygen engineering strategy is proposed totune the oxygen species in N-doped porous carbon nanofibers(NPCNFs-O) via a facile electrospinning method, in which beta-cyclodextrin acts as the pore inducer and oxygen regulator.Benefitting from the large specific surface area and synergistic effectof N,O codoping, the NPCNF-O catalyst exhibits superior ORR(E1/2= 0.85 V vs reversible hydrogen electrode (RHE)) and OER(Ej=10= 1.556 V vs RHE) activities with excellent stability. Bothexperimental and theoretical calculations verify the crucial role ofcarboxyl groups, which regulate the local charge density and reduce the reaction energy barrier for enhancing the oxygenelectrocatalytic activity. Moreover, a rechargeable zinc-air battery using NPCNF-O as the air cathode demonstrates a maximumpower density of 125.1 mW cm-2and long-term durability. Importantly, NPCNF-O can be served as an integrated freestandingelectrode for portable zinc-air batteries. The work brings brilliant fundamental insights for constructing efficient metal-free carbonmaterial catalysts for future energy conversion and storage systems.

Automated summary

The study proposes a simple oxygen engineering strategy to improve the performance of heteroatom-doped carbon catalysts for oxygen reduction/evolution reactions. The crucial role of carboxyl groups in enhancing the oxygen electrocatalytic activity is verified through experimental and theoretical calculations. Additionally, the catalyst shows potential applications in zinc-air batteries.