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

Abstract

Controllable designing of heteroatom-doped carbon catalysts provides an insightful strategy for boosting the performance and kinetics of the oxygen reduction/evolution reaction (ORR/OER). However, the role of oxygen species is usually omitted. Herein, a facile oxygen engineering strategy is proposed to tune the oxygen species in N-doped porous carbon nanofibers (NPCNFs-O) via a facile electrospinning method, in which β-cyclodextrin acts as the pore inducer and oxygen regulator. Benefitting from the large specific surface area and synergistic effect of 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. Both experimental and theoretical calculations verify the crucial role of carboxyl groups, which regulate the local charge density and reduce the reaction energy barrier for enhancing the oxygen electrocatalytic activity. Moreover, a rechargeable zinc–air battery using NPCNF-O as the air cathode demonstrates a maximum power density of 125.1 mW cm–2 and long-term durability. Importantly, NPCNF-O can be served as an integrated freestanding electrode for portable zinc–air batteries. The work brings brilliant fundamental insights for constructing efficient metal-free carbon material catalysts for future energy conversion and storage systems.